Unit I: Diversity of Living World Chapter 1 Living World

Learning Objectives

The learner will be able to, • Differentiate living and non-living things. • Appreciate the attributes of living organisms. • Compare the different classifications proposed by biologists. • Recognize the general characters, structure and reproduction of Bacteria. • Identify the characteristic features of Archaebacteria, Cyanobacteria, Earth was formed some 4.6 billion years ­Mycoplasma and Actinomycetes. ago. It is the life supporting planet with • Describe the characteristic features land forms like mountains, plateaus, of fungi. glaciers, etc., Life on earth exists within • Discuss on the structure and uses a complex structure called biosphere. of Mycorrhizae and Lichens. There exist many mysteries and wonders in the living world some are not visible but the activity of some capture the attention of all. For example the response Chapter Outline of sunflower­ to the sunlight, the twinkling 1.1 Attributes of Living firefly in the dark forest, the rolling water organisms droplets on the surface of lotus leaf, the closure of the leaf of venus fly trap on 1.2 Viruses insect touch and a squid squeezing ink to 1.3 Classification of escape from its predator. From this it is Living world clear that the wonder planet earth harbors 1.4 Bacteria both landforms and life forms. Have you 1.5 Fungi thought of DNA molecule? It is essential for the regulation of life and is made up

1

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 1 02-06-2018 13:43:38 of carbon, hydrogen, oxygen, nitrogen cells. Therefore, growth in living thing is and phosphorus thus nonliving and living intrinsic. In unicellular organisms like things exist together to make our planet bacteria and amoeba growth occurs by cell unique. division and such cell division also leads According to a survey made by to the growth of their population. Hence, Mora et al., 2011 the number of estimated growth and reproduction are mutually species on earth is 8.7 million. The living inclusive events. world includes microbes, plants, animals Cellular structure and human beings which possess unique and distinct characteristic feature. All living organisms are made up of cells which may be prokaryotic or eukaryotic. 1.1 Attributes of living organisms Prokaryotes are unicellular, lack membrane bound nuclei and organelles The attributes of living organisms are given like mitochondria, endoplasmic reticulum, below and is represented in Figure 1.1 golgi bodies and so on (Example: Bacteria and Blue green algae). In Eukaryotes a Growth Nutrition Movement definite nucleus and membrane bound organelles are present. Eukaryotes may ATTRIBUTES Metabolism OF LIVING Reproduction be unicellular (Amoeba) or multicellular ORGANISMS (Oedogonium). Reproduction Respiration Irritability Excretion Reproduction is one of the fundamental Figure 1.1: Attributes of living organisms characteristic features of living organisms. It is the tendency of a living organism Growth to perpetuate its own species. There are two types of reproduction namely Growth is an intrinsic property of all asexual and sexual. Asexual reproduction living organisms through which they can (Figure 1.2) refers to the production of increase cells both in number and mass. the progeny possessing features more Unicellular and multicellular organisms or less similar to those of parents. The grow by cell division. In plants, growth sexual reproduction brings out variation is indefinite and occurs throughout through recombination. Asexual their life. In animals, growth is definite reproduction in living organisms occurs and occurs for some period. However, by the production of conidia (Aspergillus, cell division occurs in living organisms Penicillium), budding (Hydra and ), to repair and heal the worn out tissues. binary fission (Bacteria and Amoeba) Growth in non-living objects is extrinsic. fragmentation (Spirogyra), protonema Mountains, boulders and sand mounds (Mosses) and regeneration (Planaria). grow by simple aggregation of material Exceptions are the sterile worker bees and on the surface. Living cells grow by the mules addition of new protoplasm within the

2

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 2 02-06-2018 13:43:38 is essential for the living organism to maintain internal condition to survive in the environment. Movement, Nutrition, Respiration and Excretion are also considered as the property of living things. (a) (b) The levels of organization in living organism begin with atoms and end in Biosphere. Each level cannot exist in isolation instead they form levels of integration as given in Figure 1.3. Metabolism The sum total of all the chemical reactions taking place in a cell of living (c) (d) organism is called metabolism. It is broadly divided into anabolism and Figure 1.2: Types of Asexual Reproduction catabolism. The difference between (a) Conidia formation-Penicillium, anabolism and catabolism is given in (b) Budding-Yeast, (c) Fragmentation- Table 1.1 Spirogyra, (d) Regeneration-Planaria Table 1.1: Difference between Response to stimuli anabolism and catabolism All organisms are capable of sensing their Anabolism Catabolism environment and respond to various physical, chemical and biological stimuli. Building up Breaking down Animals sense their surroundings by sense process process organs. This is called Consciousness. Smaller Larger molecule Plants also respond to the stimuli. Bending molecules break into smaller of plants towards sunlight, the closure of combine together units leaves in touch-me-not plant to touch are to form larger some examples for response to stimuli molecule in plants. This type of response is called Chemical energy The stored chemical Irritability. is formed and energy is released Homeostasis stored and used Property of self-regulation and tendency Example: Example: to maintain a steady state within an Synthesis of Breaking down of external environment which is liable proteins from glucose to CO2 and to change is called Homeostasis. It amino acids water

3

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 3 02-06-2018 13:43:41 Biosphere Did you go through the headlines of news papers in recent times? Have you heard Ecosystem III Ecosystem of the terms EBOLA, ZIKA, AIDS, SARS, H1N1 etc? There are serious entities which Community are considered as “Biological Puzzle” Population and cause disease in man. They are called viruses. We have learnt about the attributes Individual organism II Individual organism of living world in the previous chapter. Organ systems Now we shall discuss about viruses which Living connect the living and nonliving world. Organs The word virus is derived from Tissues Latin meaning ‘Poison’. Viruses are Living cells sub-microscopic, obligate intracellular Living cells I parasites. They have nucleic acid core

Organelles Colloids surrounded by protein coat. Viruses in their native state contain only a single Molecules & Crystals Compounds type of nucleic acid which may be either DNA or RNA. The study of viruses is Mixture Living Non Atoms called Virology. Figure 1.3: The levels of organization and integration in living organism

Activity 1.1 Collect Vallisneria leaves or Chara from nearby aquarium and observe a leaf or Chara thallus (internodal region)under the microscope. You could see cells clearly under the microscope. Could W.M. Stanley you notice the movement of cytoplasm? (1904-1971) The movement of cytoplasm is called An American Scientist obtained virus cytoplasmic streaming or cyclosis. in crystallised form from infected tobacco juice in the year 1935. 1.2 Viruses He was jointly awarded “Nobel Prize” in Chemistry in 1946 with J.H. Northrop.

1.2.1 Milestones in Virology 1796 Edward Jenner used vaccination for small pox 1886 Adolf Mayer demonstrated the infectious nature of Tobacco mosaic virus using sap of mosaic leaves

4

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 4 02-06-2018 13:43:41 1892 Dimitry Ivanowsky proved that 1.2.3 Characteristic features of Viruses viruses are smaller than bacteria Living Characters 1898 M.W. Beijierink defined the infectious agent in tobacco leaves • Presence of nucleic acid and protein. as ῾Contagium vivum fluidum’ • Capable of mutation 1915 F.W.Twort identified Viral infection • Ability to multiply within living cells. in Bacteria • Able to infect and cause diseases in 1917 d’Herelle coined the term living beings. ‘Bacteriophage’ 1984 Luc Montagnier and Robert Gallo • Show irritability. discovered HIV (Human Immuno • Host –specific Deficiency Virus). Non-living Characters 1.2.2 Size and shape • Can be crystallized. Viruses are ultramicroscopic particles. They • Absence of metabolism. are smaller than bacteria and their diameter range from 20 to 300 nm (1nm = 10-9metres). • Inactive outside the host. Bacteriophage measures about 10-100 nm in • Do not show functional autonomy. size. The size of TMV is 300×20 nm. • Energy producing enzyme system is absent. Generally viruses are of three types based on shape and symmetry (Figure 1.4). 1.2.4 Classification of Viruses i. Cuboid symmetry – Example: Among various classifications proposed Adenovirus, Herpes virus. for viruses the classification given by ii. Helical symmetry – Example: David Baltimore in the year 1971 is Influenza virus, TMV. given below. The classification is based iii. Complex or Atypical – Example: on mechanism of RNA production, the Bacteriophage, Vaccinia virus. nature of the genome (single stranded –ss

RNA

Head Fibre DNA Capsid Collar DNA Sheath

Protein Basal plate

Tail fibre (a) (b) (c)

(a) Adenovirus (b) Tobacco Mosaic virus (c) T4 Bacteriophage Figure 1.4: Shapes of Viruses

5

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 5 02-06-2018 13:43:42 Table 1.2: Different Classes of viruses Class Example Class 1 - Viruses with dsDNA Adenoviruses Class 2 –Viruses with (+) sense ssDNA Parvo viruses Class 3 –Viruses with dsRNA Reo viruses Class 4 –Viruses with (+) sense ssRNA Toga viruses Class 5 – Viruses with (–) antisense ssRNA Rhabdo viruses Class 6 – Viruses with (+) sense ss RNA –RT that replicate with DNA Retro viruses intermediate in life cycle Class 7 – Viruses with ds DNA – RT that replicate with RNA Hepadna intermediate in life cycle viruses

or double stranded - ds ), RNA or DNA, 1.2.5 Tobacco Mosaic Virus (TMV) the use of reverse transcriptase(RT), ss Tobacco mosaic virus was discovered RNA may be (+) sense or (–) antisense. in 1892 by Dimitry Ivanowsky from the Viruses are classified into seven classes Tobacco plant. Viruses infect healthy (Table 1.2). plants through vectors like aphids, locusts Viral genome etc. The first visible symptom of TMV is discoloration of leaf colour along the Each virus possesses only one type of veins and show typical yellow and green nucleic acid either DNA or RNA. The mottling which is the mosaic symptom. nucleic acid may be in a linear or circular The downward curling and distortion of form. Generally nucleic acid is present young apical leaves occurs, plant becomes as a single unit but in wound tumour stunted and yield is affected. virus and in influenza virus it is found in segments. The viruses possessing Structure DNA are called ‘Deoxyviruses’ whereas Electron microscopic studies have revealed those possessing RNA are called that TMV is a rod shaped (Figure 1.4b) ‘Riboviruses’. Majority of animal helical virus measuring about 280x150µm and bacterial viruses are DNA viruses with a molecular weight of 39x106 Daltons. (HIV is the animal virus which possess The virion is made up of two constituents, a RNA). Plant viruses generally contain protein coat called capsid and a core called RNA (Cauliflower Mosaic virus possess nucleic acid. The protein coat is made up DNA). The nucleic acids may be single of approximately 2130 identical protein stranded or double stranded. On the subunits called capsomeres which are basis of nature of nucleic acid viruses present around a central single stranded are classified into four Categories. They RNA molecule. The genetic information are Viruses with ssDNA (Parvoviruses), necessary for the formation of a complete dsDNA (Bacteriophages), ssRNA (TMV) TMV particle is contained in its RNA. The RNA consists of 6,500 nucleotides. and dsRNA(wound tumour virus).

6

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 6 02-06-2018 13:43:42 1.2.6 Bacteriophage sites present on bacterial cell surface. The Viruses infecting bacteria are called lipopolysaccharides of tail fibres act as Bacteriophages. It literally means ‘eaters receptor in phages. The process involving of bacteria’ (Gr: Phagein = to eat). Phages the recognition of phage to bacterium are abundant in soil, sewage water, fruits, is called landing. Once the contact vegetables, and milk. is established between tail fibres and bacterial cell, tail fibres bend to anchor Structure of T4 bacteriophage the pins and base plate to the cell surface.

The T4 phage is tadpole shaped and This step is called pinning. consists of head, collar, tail, base plate and (ii) Penetration fibres (Figure 1.4). The head is hexagonal The penetration process involves mechanical which consists of about 2000 identical and enzymatic digestion of the protein subunits. The long helical tail of the host. At the recognition site phage consists of an inner tubular core which is digests certain cell wall structure by viral connected to the head by a collar. There enzyme (lysozyme). After pinning the tail is a base plate attached to the end of tail. sheath contracts (using ATP) and appears The base plate contains six spikes and tail shorter and thicker. After contraction of fibres. These fibres are used to attach the the base plate enlarges through which phage on the cell wall of bacterial host DNA is injected into the cell wall without during replication. A dsDNA molecule of using metabolic energy. The step involving about 50 µm is tightly packed inside the ­injection of DNA particle alone into the head. The DNA is about 1000 times longer bacterial cell is called Transfection. The than the phage itself. empty protein coat leaving outside the cell 1.2.7 Multiplication or Life Cycle of is known as ‘ghost’. Phages (iii) Synthesis Phages multiply through two different This step involves the degradation of types of life cycle. a. Lytic or Virulent cycle bacterial chromosome, protein synthesis b. Lysogenic or Avirulent life cycle and DNA replication. The phage nucleic acid takes over the host biosynthetic a. Lytic Cycle machinery. Host DNA gets inactivated and During lytic cycle of phage, disintegration breaks down. Phage DNA suppresses the of host bacterial cell occurs and the synthesis of bacterial protein and directs progeny virions are released (Figure 1.5a). the metabolism of the cell to synthesis The steps involved in the lytic cycle are as the proteins of the phage particles and follows: simultaneously replication of Phage DNA (i) Adsorption also takes place. (iv) Assembly and Maturation Phage (T4) particles interact with cell wall of host (E. coli). The phage tail The DNA of the phage and protein coat are makes contact between the two, and tail synthesized separately and are assembled fibres recognize the specific receptor to form phage particles. The process of

7

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 7 02-06-2018 13:43:42 Capsid assembling the phage particles is known as DNA maturation. After 20 minutes of infection Bacterial about 300 new phages are assembled. Adsorption genome (v) Release The phage particle gets accumulated Phage Penetration DNA inside the host cell and are released by the lysis of host cell wall. b. Lysogenic Cycle Synthesis In the lysogenic cycle the phage DNA Host cell gets integrated into host DNA and gets multiplied along with nucleic acid of the host. No independent viral particle is Assembly and maturation formed (Figure 1.5b). As soon as the phage injects its linear DNA into the host cell, it becomes circular and integrates into the bacterial Release chromosome by recombination. The Release of new phage integrated phage DNA is now called particle prophage. The activity of the prophage (a) Phage gene is repressed by two repressor proteins which are synthesized by phage genes. Phage DNA This checks the synthesis of new phages Bacterial chromosome within the host cell. However, each time the bacterial cell divides, the prophage multiplies along with the bacterial Circular phage DNA chromosome. On exposure to UV radiation and chemicals the excision of phage DNA may occur and results in lytic cycle. Virion is an intact infective virus particle which is non-replicating outside a host cell. Prophage Viroid is a circular molecule of ssRNA without a capsid and was discovered by T.O.Diener in the year 1971. The RNA of Reproducing viroid has low molecular weight. Viroids bacterial cell cause citrus exocortis and potato spindle (b) tuber disease in plants. Virusoids were discovered by Figure 1.5: Multiplication cycle of phage J.W.Randles and co-workers in 1981. (a) Lytic cycle, (b) Lysogenic cycle They are the small circular RNAs which

8

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 8 02-06-2018 13:43:42 are similar to viroids but they are always 1.2.8 Viral diseases linked with larger molecules of the viral Viruses are known to cause disease RNA. in plants, animals and Human beings Prions were discovered by Stanley (Figure 1.6). A list of viral disease is given B. Prusiner in the year 1982 and are in Table 1.3 proteinaceous infectious particles. They are the causative agents for about a dozen ­fatal ­degenerative disorders of the ­central ­nervous system of humans and other ­animals. For example Creutzfeldt – Jakob Disease (CJD), Bovine Spongiform Encephalopathy (BSE) – commonly known as mad cow disease and scrapie disease of sheep. (a) Viruses infecting blue green algae are called Cyanophages and are first Blister reported by Safferman and Morris in like the year 1963(Example: LPP1 - Lyngbya, pustules­ Plectonema and Phormidium). Similarly, Hollings(1962) reported viruses infecting cultivated and (b) causing die back disease. The viruses attacking fungi are called Mycoviruses Figure 1.6: Viral diseases (a) Mosaic or Mycophages. disease of tomato, (b) Symptom of Chicken pox

Table 1.3: Viral diseases Plant diseases Animal diseases Human diseases 1. Tobacco mosaic 1. Foot and mouth disease 1. Common cold 2. Cauliflower mosaic of cattle 2. Hepatitis B 3. Sugarcane mosaic 2. Rabies of dog 3. Cancer 4. Potato leaf roll 3. Encephalomyelitis of 4. SARS(Severe Acute Respiratory Syndrome) 5. Bunchy top of banana horse 5. AIDS(Acquired Immuno 6. Leaf curl of papaya Deficiency Syndrome) 7. Vein clearing of Lady’s 6. Rabies finger 7. Mumps 8. Rice tungro disease 8. Polio 9. Cucumber mosaic 9. Chikungunya 10. Tomato mosaic disease 10. Small Pox 11. Chicken pox 12. Measles

9

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 9 02-06-2018 13:43:47 Theophrastus, “Father of Botany” used the morphological characters to classify plants into trees, shrubs and herbs. Aristotle classified animal into two groups. i.e., Enaima (with red blood) and Anaima (without red blood). Carl Streaks on Tulip flowers are due to Linnaeus classified living world into Tulip breaking Virus which belong to two groups namely Plants and Animals Potyviridae group. based on morphological characters. His Viruses of Baculoviridae group are classification faced major setback because commercially exploited as insecticides. prokaryotes and Eukaryotes were grouped Cytoplasmic polyhedrosis Granulo together. Similarly fungi, heterotrophic viruses and Entomopox virus were organisms were placed along with the employed as potential insecticides. photosynthetic plants. In course of time, the development of tools compelled 1.3 Classification of Living World taxonomists to look for different areas like cytology, anatomy, embryology, molecular From the Previous chapter we know that the biology, phylogeny etc., for classifying planet earth is endowed with living and non organisms on earth. Thus new dimensions -living things. In our daily life we see several to classifications were put forth from time things in and around us. Imagine you are on to time. a trip to Hill station. You are enjoying the beauty of mountains, dazzling colour of the 1.3.1 Need of Classification flowers, and melodious sound of the birds. Classification is essential to achieve You may be capturing most of the things following needs you come across in the form of photography. • To relate things based on common Now, from this experience can you mention characteristic features. the objects you came across? Can you record your observations and tabulate them. How • To define organisms based on the will you organize the things? Will you place salient features. mountain and flowers together or tall trees • Helps in knowing the relationship and trailing herbs in one category or place amongst different groups of it in different category? If you place it in organisms. different category, what made you to place • It helps in understanding the them in different category? So classification evolutionary relationship between is essential and could be done only by organisms. understanding and comparing the things based on some characters. In this chapter 1.3.2 Classification of Living world we shall learn about classification of living A comparison of classification proposed world. for classification of living world is given Many attempts have made in the in Table 1.4 past to classify the organisms on earth.

10

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 10 02-06-2018 13:43:48 Table 1.4: Systems of Classification Two Kingdom Three Kingdom Four Kingdom Five Kingdom

Carl Linnaeus Ernst Haeckel Copeland R.H. Whittaker (1735) (1866) (1956) (1969) 1. Plantae 1. Protista 1. Monera 1. Monera 2. Animalia 2. Plantae 2. Protista 2. Protista 3. Animalia 3. Plantae 3. Fungi 4. Animalia 4. Plantae 5. Animalia

1.3.3 Five Kingdom Classification heterotrophic organisms, cell wall R.H.Whittaker, an American taxonomist lacking and cell wall bearing organisms proposed five kingdom classification in thus making these two groups more the year 1969. The Kingdoms include heterogeneous. Monera, Protista, Fungi, Plantae and • Viruses were not included in the Animalia (Figure 1.7). The criteria system. adopted for the classification include cell structure, thallus organization, mode of Carl Woese and co-workers in the year nutrition, reproduction and phylogenetic 1990 introduced three domains of life viz., relationship. A comparative account of Bacteria, Archaea and Eukarya based the salient features of each kingdom is on the difference in rRNA nucleotide given in Table 1.5 sequence, lipid structure of the cell membrane. A revised six Kingdom Merits classification for living world was • The classification is based on the proposed by Thomas Cavalier-Smith in complexity of cell structure and the year 1998 and the Kingdom Monera organization of thallus. is divided in to Archaebacteria and • It is based on the mode of nutrition Eubacteria. Recently Ruggerio et al., 2015 • Separation of fungi from plants published a seven kingdom classification which is a practical extension of • It shows the phylogeny of the organisms Thomas Cavalier’s six kingdom scheme. Demerits According to this classification there are two superkingdoms (Prokaryota • The kingdom Monera and protista and Eukaryota) Prokaryota include accommodate both autotrophic and

11

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 11 02-06-2018 13:43:49 Fungi Animalia Plantae Basidiomycotaa AArthropoda Spepepermatophyta Annenenelidad Mollusca Pteridophyta Ascomommycoota Vertebratee NeNNematoda

mycetemyce Protochoordatao Zygomycota Echinodermataa Bryryoyophyta Myxomyce Charophytaa Chaetognatha OOomycete Phaeophhhyta DictyosteliiDictyostDictyosteliidae CChlorophyta raran Platyhelminthes Coelenterata Rhodophythyta Poriferferaera Bacillariophytaa

Mastigophora

Ciliophphorapho

Rhizopodhizopoda Cyanophyta Bacterriar Protista

Monera Figure Figure1.10 Five1.7: Five kingdom kingdom classi classificationfication

two kingdoms namely Archaebacteria and Eubacteria. Eukaryota include the Red tide is caused Protozoa, chromista, fungi, Plantae by toxic bloom of and Animalia. A new Kingdom, the Dinoflagellates like Chromista was erected and it included Gymnodinium breve and all algae whose chloroplasts contain Gonyaulax tamarensis. chlorophyll a and c, as well as various A major red tide incident in west colorless forms that are closely related coast of Florida in the year 1982 killed to them. Diatoms, Brown algae, Hundreds and thousands of fishes. cryptomonads and Oomycetes were placed under this kingdom. Activity 1.2 Visit to a pond and record the names of the biotic components of it with the help of your teacher. Tabulate the data and segregate them according to Five Kingdom classification

12

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 12 02-06-2018 13:43:49 Sponges, and Invertebrates Vertebrates Mostly motile Mostly Heterotrophic (Holozoic) absent Tissue/organ/organ Tissue/organ/organ system Eukaryotic Animalia Algae, Bryophytes, Bryophytes, Algae, Pteridophytes, and Gymnosperms Angiosperms Mostly Non-motile Mostly Autotrophic (Photosynthetic) Present (made up of of up (made Present cellulose) Tissue/organ Eukaryotic Plantae Kingdom Yeast, Mushrooms Mushrooms Yeast, and Non-motile Heterotrophic- or parasitic Saprophytic Present (made up of of up (made Present cellulose) or chitin Multicellular unicellular and Eukaryotic Fungi mparison of Five Kingdoms Five of mparison Co

Amoeba, Table 1.5: Table Chrysophytes, Chrysophytes, Dinoflagellates, Slime Euglenoids, molds, Plasmodium, Trypanosoma, Paramecium Motile or or Motile non-motile Autotrophic- Photosynthetic. Heterotrophic Present in some in some Present of up (made in cellulose), absent others Unicellular Eukaryotic Protista

Archaebacteria, Archaebacteria, Eubacteria, Cyanobacteria, and Actinomycetes Mycoplasma Motile or or Motile non-motile Autotrophic (Phototrophic, Chemoautotrophic) Heterotrophic and (parasitic saprophytic) Present of up (made and Peptidoglycan Mucopeptides) Unicellular Prokaryotic Monera Organisms Motility Nutrition Cell wall Level of organization Cell type Criteria

13

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 13 02-06-2018 13:43:49 1.4 Bacteria 1.4.1 Milestones in Bacteriology 1829 C.G. Ehrenberg coined the term Bacteria Friends or Foes? Bacterium Have you noticed the preparation of curd 1884 Christian Gram introduced in our home? A little drop of curd turns Gram staining method the milk into curd after some time. What is 1923 David H. Bergy published First responsible for this change? Why it Sours? edition of Bergey’s Manual The change is brought by Lactobacillus lactis, a bacterium present in the curd. 1928 Fredrick Griffith discovered The sourness is due to the formation of Bacterial transformation Lactic acid. Have you been a victim of 1952 Joshua Lederberg discovered of Typhoid? It is a bacterial disease caused Plasmid by Salmonella typhi, a bacterium. So we Bacteria are prokaryotic, unicellular, can consider this prokaryotic organism as ubiquitous, microscopic organisms. The friend and foe, due to their beneficial and study of Bacteria is called Bacteriology. harmful activities. Bacteria were first discovered by a Dutch scientist, Anton van Leeuwenhoek in 1676 and were called “animalcules”. 1.4.2 General characteristic features of Bacteria • They are Prokaryotic organisms and lack nuclear membrane and membrane bound organelles. • The Genetic material is called nucleoid or genophore or incipient nucleus • The cell wall is made up of Polysaccharides and proteins Robert Koch (1843–1910) • Most of them lack chlorophyll, hence Robert Heinrich Hermann Koch they are heterotrophic (Vibrio cholerae) was a German physician and but some are autotrophic and possess microbiologist. He is considered as Bacteriochlorophyll (Chromatium) the founder of modern bacteriology. • They reproduce vegetatively by Binary He identified the causal organism for fission and endospore formation. Anthrax, Cholera and Tuberculosis. • They exhibit variations which are due to The experimental evidence for the genetic recombination and is achieved concept of infection was proved by him through conjugation, transformation (Koch’s postulates). He was awarded and transduction. Nobel prize in Medicine/Physiology The shape and flagellation of the bacteria in the year 1905. varies and is given in Figure 1.8

14

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 14 02-06-2018 13:43:50 Monotrichous Coccus Diplococcus Tetracoccus Staphylococcus

Lophotrichous

Sarcina Streptococcus

Amphitrichous

Bacillus Diplobacillus

Peritrichous

Vibrio

Spirillum Atrichous

Figure 1.8: Shape and flagellation in bacteria

1.4.3 Ultrastructure of a Bacterial cell The bacterial cell reveals three layers (i) Capsule/Glycocalyx (ii) Cell wall and (iii) Cytoplasm (Figure 1.9)

Capsule Cell wall Plasma membrane

Mesosome

Cytoplasm Nucleoid (DNA)

Flagellum

Plasmid

Inclusion Polyribosome

Pilus

Figure 1.9: Ultrastructure of a bacterial cell

15

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 15 02-06-2018 13:43:51 Cytoplasm Duodenal and Gastric ulcers are caused by Cytoplasm is thick and semitransparent. Helicobacter pylori, It contains ribosomes and other cell a Gram negative inclusions. Cytoplasmic inclusions like bacterium. glycogen, poly-β-hydroxybutyrate granules, sulphur granules and gas vesicles are • Bt toxin from Bacillus thuringiensis present. finds application in raising insect resistant crops (Bt Crops). Bacterial chromosome The bacterial chromosome is a single Capsule/Glycocalyx circular DNA molecule, tightly coiled Some bacteria are surrounded by a and is not enclosed in a membrane as in gelatinous substance which is composed Eukaryotes. This genetic material is called of polysaccharides or polypeptide or both. Nucleoid or Genophore. It is amazing A thick layer of glycocalyx bound tightly to note that the DNA of E.coli which to the cell wall is called capsule. It protects measures about 1mm long when uncoiled, cell from desiccation and antibiotics. contains all the genetic information of The sticky nature helps them to attach to the organism. The DNA is not bound to substrates like plant root surfaces, Human histone proteins. The single chromosome teeth and tissues. It helps to retain the or the DNA molecule is circular and at nutrients in bacterial cell. one point it is attached to the plasma membrane and it is believed that this Cell wall attachment may help in the separation of The bacterial cell wall is granular and is two chromosomes after DNA replication. rigid. It provide protection and gives shape Plasmid to the cell. The chemical composition of cell wall is rather complex and is made up of Plasmids are extrachromosomal double Peptidoglycan or mucopeptide ( N-acetyl stranded, circular, self-replicating, autonomous glucosamine, N-acetyl muramic acid elements. They contain genes for fertility, and peptide chain of 4 or 5 aminoacids). antibiotic resistant and heavy metals. It One of the most abundant polypeptide also help in the production of bacteriocins called porin is present and it helps in the and toxins which are not found in bacterial diffusion of solutes. chromosome. The size of a plasmid varies from 1 to 500 kb usually plasmids contribute Plasma membrane to about 0.5 to 5.0% of the total DNA of The plasma membrane is made up of bacteria. The number of plasmids per cell lipoprotein. It controls the entry and exit varies. Plasmids are classified into different of small molecules and ions. The enzymes types based on the function. Some of them involved in the oxidation of metabolites are F (Fertility) factor, R (Resistance) (i.e., the respiratory chain) as well as the plasmids, Col (Colicin) plasmids, Ri photosystems used in photosynthesis are (Root inducing) plasmids and Ti (Tumour present in the plasma membrane. inducing) plasmids.

16

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 16 02-06-2018 13:43:51 Mesosomes Danish Physician Christian Gram in These are localized infoldings of plasma the year1884. It is a differential staining membrane produced into the cell in the procedure and it classifies bacteria into form of vesicles, tubules and lamellae. two classes - Gram positive and Gram They are clumped and folded together to negative. The steps involved in Gram maximize their surface area and helps in staining procedure is given in Figure respiration and in binary fission. 1.10. The Gram positive bacteria retain crystal violet and appear dark violet Polysomes / Polyribosomes whereas Gram negative type loose the The ribosomes are the site of protein crystal violet and when counterstained synthesis. The number of ribosome per by safranin appear red under a cell varies from 10,000 to 15,000. The microscope. ribosomes are 70S type and consists of two subunits (50S and 30S). The ribosomes Prepare a smear of bacterial culture are held together by mRNA and form polyribosomes or polysomes. Stain with Crystal violet for 30 seconds Flagella Certain motile bacteria have numerous thin hair like processes of variable length Rinse in distilled water for 2 seconds emerge from the cell wall called flagella. It is 20–30 μm in diameter and 15 μm in Grams Iodine for 1 minute length. The flagella of Eukaryotic cells contain 9+2 microtubles but each flagellum in bacteria is made up of a single fibril. Rinse in distilled water Flagella are used for locomotion. Based on the number and position of flagella there Wash in 95% ethanol or acetone are different types of bacteria (Figure 1.8) for 10 to 30 seconds Fimbriae or Pili Pili or fimbriae are hair like appendages Rinse in distilled water found on surface of cell wall of gram-negative bacteria (Example: Safranin for 30–60 seconds Enterobacterium). The pili are 0.2 to 20 µm long with a diameter of about 0.025µm. In addition to normal pili there are special Rinse in distilled water and blot type of pili which help in conjugation called sex pili are also found. Observe under microscope 1.4.4 Gram staining procedure The Gram staining method to Figure 1.10: Steps involved in Gram differentiate bacteria was developed by Staining

17

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 17 02-06-2018 13:43:51 Most of the gram positive cell wall 2. Outer membrane 3.Lipopolysaccharide. contain considerable amount of teichoic Thus the different results in the gram stain acid and teichuronic acid. In addition, are due to differences in the structure and they may contain polysaccharide composition of the cell wall (Figure 1.11). molecules. The gram negative cell wall The difference between Gram Positive contains three components that lie outside and Gram negative bacteria is given in the peptidoglycan layer. 1. Lipoprotein Table 1.6.

GRAM POSITIVE GRAM NEGATIVE

Outer membrane Lipoproteins Peptidoglycan Periplasmic space Cytoplasmic membrane

Lipopolysaccharides Porin Protein

Figure 1.11: Difference between Gram positive and Gram negative bacteria

Table 1.6: Difference between Gram Positive and Gram Negative Bacteria S.No Characteristics Gram positive Bacteria Gram negative Bacteria 1. Cell wall Single layered with Triple layered with 0.015µm-0.02µm 0.0075µm–0.012µm thick 2. Rigidity of cell wall Rigid due to presence of Elastic due to presence of Peptidoglycans lipoprotein-polysaccharide mixture 3. Chemical composition Peptidoglycans-80% Peptidoglycans-3 to 12% Polysaccharide-20% rest is polysaccharides and Teichoic acid present lipoproteins. Teichoic acid absent 4. Outer membrane Absent Present 5. Periplasmic space Absent Present 6. Susceptibility to Highly susceptible Low susceptible penicillin 7. Nutritional requirements Relatively complex Relatively simple 8. Flagella Contain 2 basal body rings Contain 4 basal body rings 9. Lipid and lipoproteins Low High 10. Lipopolysaccharides Absent Present

18

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 18 02-06-2018 13:43:51 Example: Escherichia coli and ­Salmonella What are Magnetosomes ? Capnophilic Bacteria Intracellular chains of 40-50 Bacteria which require CO2 for their magnetite (Fe3O4) particles are growth are called as capnophilic found in bacterium Aquaspirillum bacteria. Example: Campylobacter magnetotacticum and it helps the bacterium to locate nutrient rich Nutrition sediments. On the basis of their mode of nutrition bacteria are classified into two types 1.4.5 Life processes in Bacteria namely Autotrophs and Heterotrophs Respiration I Autotrophic Bacteria Bacteria which can synthesis their own Two types of respiration is found in food are called autotrophic bacteria. Bacteria. They are 1. Aerobic respiration They may be further subdivided as 2. Anaerobic respiration 1. Aerobic respiration A. Photoautotrophic bacteria:- These bacteria require oxygen as terminal Bacteria use sunlight as their source of acceptor and will not grow under energy to synthesize food. They may be anaerobic conditions (i.e. in the absence 1. Photolithotrophs: of O2) Example: Streptococcus In Photolithotrophs the hydrogen donor Obligate aerobes is an inorganic substance. Some Micrococcus species are obligate a. Green sulphur bacteria: In this type of aerobes (i.e. they must have oxygen to bacteria the hydrogen donor is H2S and survive). possess pigment called Bacterioviridin. 2. Anaerobic respiration Example: Chlorobium These bacteria do not use oxygen for b. Purple sulphur bacteria: For bacteria growth and metabolism but obtain their belong to this group the hydrogen donor energy from fermentation reactions. is Thiosulphate, Bacteriochlorophyll Example: Clostridium is present. Chlorophyll containing Facultative anaerobes chlorosomes are present Example: There are bacteria that can grow either Chromatium. using oxygen as a terminal electron acceptor 2. Photoorganotrophs or anaerobically using fermentation They utilize organic acid or alcohol as reaction to obtain energy. When a facultative hydrogen donor. Example: Purple non anaerobe such as E. coli is present at a site sulphur bacteria – Rhodospirillum. of infection like an abdominal abscess, it B. Chemoautotrophic bacteria can rapidly consume all available O2 and change to anaerobic metabolism producing They do not have photosynthetic pigment an anaerobic environment and thus allow hence they cannot use sunlight energy. the anaerobic bacteria that are present to These type of bacteria obtain energy from grow and cause disease. organic or inorganic substance.

19

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 19 02-06-2018 13:43:51 1.Chemolithotrophs This type of bacteria oxidize inorganic compound to release energy Examples Cell wall Nucleoid 1. Sulphur bacteria Endospore Thiobacillus thiooxidans 2. Iron bacteria Thick wall Ferrobacillus ferrooxidans 3. Hydrogen bacteria Hydrogenomonas Daughter cells 4. Nitrifying bacteria Nitrosomonas and Nitrobacter (a) (b) 2. Chemoorganotrophs Figure 1.12: Asexual Reproduction in This type of bacteria oxidize organic Bacteria (a) Binary fission, compounds to release energy. (b) Endospore Examples Endospores 1. Methane bacteria – Methanococcus During unfavourable condition bacteria 2. Acetic acid bacteria – Acetobacter produce endospores. Endospores are 3. Lactic acid bacteria – Lactobacillus produced in Bacillus megaterium, Bacillus sphaericus and Clostridium tetani. II. Heterotrophic Bacteria Endospores are thick walled resting They are Parasites (Clostridium, . During favourable condition, they Mycobacterium) Saprophytes (Bacillus germinate and form bacteria. mycoides) or Symbiotic (Rhizobium in Sexual Reproduction root nodules of leguminous crops). Typical sexual reproduction involving the 1.4.6 Reproduction in Bacteria formation and fusion of gametes is absent Bacteria reproduces asexually by Binary in bacteria. However gene recombination fission, conidia and endospore formation can occur in bacteria by three different (Figure 1.12). Among these Binary fission methods they are is the most common one. 1. Conjugation Binary fission 2. Transformation 3. Transduction Under favourable conditions the cell divides into two daughter cells. The 1. Conjugation nuclear material divides first and it is J. Lederberg and Edward L. Tatum followed by the formation of a simple demonstrated conjugation in E. coli. in the median constriction which finally results year 1946. In this method of gene transfer in the separation of two cells. the donor cell gets attached to the recipient

20

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 20 02-06-2018 13:43:51 Heat-Killed R-Strain and Heat- cell with the help of pili. The pilus grows (a) R-Strain S-Strain S-Strain killed S- Strain in size and forms the conjugation tube. The plasmid of donor cell which has the F+ (fertility factor) undergoes replication. Only one strand of DNA is transferred to the recipient cell through conjugation tube. The recipient completes the structure

of double stranded DNA by synthesizing MouseMl liives MouseMd diesi MouseMl liives MouseMd diesi the strand that complements the strand acquired from the donor (Figure 1.13).

Conjugation pilus Chromosome F plasmid F+ cell F- cell

F+ cell F+ cell

Figure 1.13: Conjugation

2. Transformation Transfer of DNA from one bacterium (b) to another is called transformation (Figure 1.14). In 1928 the bacteriologist Figure 1.14: Transformation in Bacteria Frederick Griffith demonstrated (a) Griffith’s experiment on Transformation transformation in Mice using (b) Mechanism of Transformation Diplococcus pneumoniae. Two strains of this bacterium are present. One strain cells and R-type cells were injected produces smooth colonies and are into the mouse. The mouse died. The virulent in nature (S type) In addition avirulent rough strain of Diplococcus another strain produced rough colonies had been transformed into S-type cells. and are avirulent (R type). When S-type The hereditary material of heat killed of cells were injected into the mouse, S-type cells had transformed R-type cell the mouse died. When R-type of cells into virulent smooth strains. Thus the were injected, the mouse survived. phenomenon of changing the character He injected heat killed S-type cells of one strain by transferring the DNA of into the mouse the mouse did not die. another strain into the former is called When the mixture of heat killed S-type Transformation.

21

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 21 02-06-2018 13:43:52 3. Transduction bacterial DNA is called Generalised Zinder and Lederberg (1952) discovered transduction. Transduction in Salmonella typhimurum. (ii) Specialized or Restricted Transduction Phage mediated DNA transfer is called The ability of the bacteriophage to carry Transduction (Figure 1.15). only a specific region of the bacterial Transduction is of two types DNA is called specialized or restricted (i) Generalized Transduction (ii) Specialized transduction. or Restricted Transduction. 1.4.7 Economic importance of Bacteria (i) Generalized Transduction Bacteria are both beneficial and Harmful. The ability of a bacteriophage to carry The beneficial activities of bacteria are genetic material of any region of given in Table 1.7

Phage Phage DNA

Bacterial chromosome

Virulent Defective phage particle

Defective particle Recipient Cell

Generalised Transduction Specialised Transduction Figure 1.15: Transduction in Bacteria

22

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 22 02-06-2018 13:43:52 Table 1.7: Economic importance of Bacteria Beneficial aspects Bacteria Role 1. Soil fertility Ammonification 1. Bacillus ramosus Convert complex proteins in the dead 2. Bacillus mycoides bodies of plants and animals into ammonia which is later converted into ammonium salt Nitrification 1. Nitrobacter Convert ammonium salts into nitrites and 2. Nitrosomonas nitrates Nitrogen fixation 1. Azotobacter (i) Converting atmospheric nitrogen into 2. Clostridium organic nitrogen 3. Rhizobium (ii) The nitrogenous compounds are also oxidized to nitrogen (iii) All these activities of bacteria increase soil fertility 2. Antibiotics 1. Streptomycin Streptomyces griseus It’s cures urinary infections, tuberculosis, meningitis and pneumonia 2. Aureomycin Streptomyces aureofaciens It’s used as a medicine to treat whooping cough and eye ­infections 3. Chloromycetin Streptomyces venezuelae It cure typhoid fever 4. Bacitracin Bacillus licheniformis It is used to treat syphilis 5. Polymyxin Bacillus polymyxa It cure some bacterial diseases 3. Industrial Uses 1. Lactic acid Streptococcus lactis and Convert milk sugar lactose into lactic acid Lactobacillus bulgaricus 2. Butter Streptococcus lactis, Leuconostoc citrovorum 3. cheese Lactobacillus acidophobus, Convert milk into butter, cheese, curd and Lactobacillus lactis yoghurt 4. Curd Lactobacillus lactis 5. Yoghurt Lactobacillus bulgaricus 6. Vinegar Acetobacter aceti This bacteria oxidizes ethyl alcohol (Acetic acid) obtained from molasses by fermentation to vinegar(acetic acid) (Continued) 23

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 23 02-06-2018 13:43:52 7. Alcohol and Clostridium acetobutylicum Alcohols and acetones are prepared from Acetone molasses by fermentation activity of the (i) Butyl alcohol anaerobic bacterium (ii) Methyl ­alcohol 8. Retting of fibres Clostridium tertium The fibres from the fibre yielding plants are separated by the action of Clostridium is called retting of fibres Escherichia coli Living in the intestine of human beings produce large quantities of vitamin K and 9. Vitamins vitamin B complex

Clostridium acetobutylicum Vitamin B2 is prepared by the fermentation of sugar 10. Curing of Tea Mycococcus candisans, The special flavor and aroma of the tea and Tobacco Bacillus megatherium and tobacco are due to fermentation

Bacteria are known to cause disease in plants, animals and Human beings. The List is given in Table 1.8, 1.9, 1.10 and Figure 1.16

Table 1.8: Plant diseases caused by Bacteria S.No. Name of the Host Name of the disease Name of the pathogen 1. Rice Bacterial blight Xanthomonas oryzae 2. Apple Fire blight Erwinia amylovora 3. Carrot Soft rot Erwinia caratovora 4. Citrus Citrus canker Xanthomonas citri 5. Cotton Angular leaf spot Xanthomonas malvacearum 6. Potato Ring rot Clavibacter michiganensis subsp. sepedonicus 7. Potato Scab Streptomyces scabies

Table 1.9: Animal diseases caused by Bacteria S. No Name of the Animal Name of the disease Name of the pathogen 1. Sheep Anthrax Bacillus anthracis 2. Cattle Brucellosis Brucella abortus 3. Cattle Bovine tuberculosis Mycobacterium bovis 4. Cattle Black leg Clostridium chanvei

24

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 24 02-06-2018 13:43:52 Table 1.10: Human diseases caused by Bacteria S.No Name of the disease Name of the pathogen 1. Cholera Vibrio cholerae 2. Typhoid Salmonella typhi 3. Tuberculosis Mycobacterium tuberculosis 4. Leprosy Mycobacterium leprae 5. Pneumonia Diplococcus pneumonie 6. Plague Yersinia pestis 7. Diphtheria Corynebacterium diptheriae 8. Tetanus Clostridium tetani 9. Food poisoning Clostridium botulinum 10. Syphilis Treponema pallidum

and prepare a smear by squeezing the content into a clean slide. Follow Gram staining method and identify the bacteria.

Bacteria forms (a) (b) Biofilms and leads Figure 1.16: Plant diseases caused by to dental caries bacteria (a) Citrus canker (b) Potato scab and Urinary tract infection (UTI) Have you heard about the word Ralstonia synthesize PHB (Poly-β- “Probiotics” hydroxybutyrate) a microbial plastic which is biodegradable.

1.4.8 Archaebacteria Archaebacteria are primitive prokaryotes and are adapted to thrive in extreme environments like hot springs, high salinity, low pH and so on. They are mostly Probiotic milk products, tooth paste are chemoautotrophs. The unique feature of available in the Market. Lactobacillus, this group is the presence of lipids like Bifidobacterium are used to prepare glycerol & isopropyl ethers in their cell probiotic yoghurt and tooth paste membrane. Due to the unique chemical composition the cell membrane show Activity 1.3 resistance against cell wall antibiotics and Collect some root nodules of leguminous lytic agents. Example: Methanobacterium, crops. Draw diagram. Wash it in tap water Halobacterium, Thermoplasma.

25

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 25 02-06-2018 13:43:55 calcium carbonate. They have a geological • Pseudomonas age of 2.7 billion years. Their abundance putida is a superbug in the fossil record indicates that (genetically engineered) cyanobacteria helped in raising the level which breakdown of free oxygen in the atmosphere. hydrocarbons. Cyanobacteria are popularly called • “Pruteen” is a single cell protein as 'Blue green algae' or 'Cyanophyceae'. derived from Methylophilus and They are photosynthetic, prokaryotic Methylotropus. organisms. According to evolutionary • Agrobacterium tumefaciens cause record Cyanobacteria are primitive crown gall disease in plants but its forms and are found in different inherent tumour inducing principle habitats. Most of them are fresh water helps to carry the desired gene and few are marine (Trichodesmium into the plant through Genetic and Dermacarpa) Trichodesmium engineering. erythraeum a cyanobacterium imparts • Thermus aquaticus is a thermophilic red colour to sea (Red sea). Species of gram negative bacteria which Nostoc, Anabaena lead an endophytic produces Taq Polymerase a key life in the coralloid root of Cycas, enzyme for Polymerase Chain leaves of aquatic fern Azolla and Reaction (PCR). thallus of hornworts like Anthoceros • Methanobacterium is employed in by establishing a symbiotic association biogas production. Halobacterium, and fix atmospheric nitrogen. Members an extremophilic bacterium grows like Gloeocapsa, Nostoc, Scytonema are in high salinity. It is exploited for found as phycobionts in lichen thalli the production β carotene. Salient features • The members of this group are 1.4.9 Cyanobacteria (Blue Green Algae) prokaryotes and lack motile How old are Cyanobacteria? reproductive structures. Stromatolites reveals the truth • The thallus is unicellular in Chroococcus, Colonial in Gloeocapsa and filamentous trichome in Nostoc. • Gliding movement is noticed in some species(Oscillatoria). • The protoplasm is differentiated into central region called centroplasm and peripheral region bearing chromatophore called chromoplasm. • The photosynthetic pigments include c-phyocyanin and c-phycoerythrin Stromatolites are deposits formed when along with myxoxanthin and colonies of cyanobacteria bind with myxoxanthophyll.

26

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 26 02-06-2018 13:43:56 • The reserve food material is Chroococcus Gloeocapsa Nostoc Cyanophycean starch. • In some forms a large colourless cell is found in the terminal or intercalary position called Heterocysts. They are involved in nitrogen fixation. • They reproduce only through vegetative Spirulina methods and produce Akinetes (thick wall dormant cell formed from vegetative cell), Hormogonia (a portion of filament get detached and Fission Akinete Endospore (Synechocystis) (Anabaena) (Dermacarpa) reproduce by cell division), fission, Endospores. • The presence of mucilage around the thallus is characteristic feature of this group. Therefore, this group is also called Myxophyceae. • Sexual reproduction is absent. • Microcystis aeruginosa, Anabaena Figure 1.17: Structure and reproduction flos-aquae cause water blooms in cyanophyceae and release toxins and affect the aquatic organism. Most of them fix 1.4.10 Mycoplasma or Mollicutes atmospheric nitrogen and are used as biofertilizers (Example: Nostoc, The Mycoplasma are very small Anabaena). Spirulina is rich in (0.1–0.5µm), pleomorphic gram negative protein hence it is used as single cell microorganisms. They are first isolated protein. The thallus organisation and by Nocard and co-workers in the year methods of reproduction is given in 1898 from pleural fluid of cattle affected Figure 1.17 with bovine pleuropneumonia. They lack cell wall and appears like “Fried Egg” in culture. The DNA contains low Guanine and Cytosine content than true bacteria. They cause disease in animals and plants. Little leaf of brinjal, witches broom of legumes phyllody of cloves, sandal spike are some plant diseases caused A prokaryote takes a joy ride on by mycoplasma. Pleuropneumonia is polar bear (Aphanocapsa montana - caused by Mycoplasma mycoides. The a cynobacterium grow on the fur of a structure of Mycoplasma is given in polar bear). Figure 1.18.

27

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 27 02-06-2018 13:43:56 1.5 Fungi Cell membrane World War II and Penicillin History speaks on fungi

Ribosome

DNA Strand

Figure 1.18: Structure of Mycoplasma Alexander Fleming 1.4.11 Actinomycetes (Actinobacteria) Discovery of Penicillin in the year 1928 is a serendipity in the world of medicine. Actinomycetes are also called ‘Ray The History of World War II recorded fungi’ due to their mycelia like growth the use of Penicillin in the form of yellow They are anaerobic or facultative powder to save lives of soldiers. For this anaerobic microorganisms and are Gram discovery - The wonderful antibiotic he positive. They do not produce an aerial was awarded Nobel Prize in Medicine in . Their DNA contain high the year 1945. guanine and cytosine content (Example: Streptomyces). 1.5.1 Milestones in Frankia is a symbiotic actinobacterium 1729 P.A.Micheli conducted which produces root nodules and fixes culture experiments nitrogen in non – leguminous plants such 1767 Fontana proved that Fungi could as Alnus and Casuarina. They produce cause disease in plants multicellular . Actinomyces 1873 C.H. Blackley proved fungi could bovis grows in oral cavities and cause cause allergy in Human beings lumpy jaw. 1906 A.F.Blakeslee reported Streptomyces is a mycelial forming heterothallism in fungi Actinobacteria which lives in soil, 1952 Pontecarvo and Raper reported they impart “earthy odor” to soil after Parasexual cycle rain which is due to the presence of The word ‘’ is derived from geosmin (volatile organic compound). Latin meaning ‘’. Fungi are Some important antibiotics namely, ubiquitous, eukaryotic, achlorophyllous Streptomycin, Chloramphenicol, and heterotrophic organisms. They exist Tetracycline are produced from this in unicellular or multicellular forms. genus. The study of fungi is called mycology

28

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 28 02-06-2018 13:43:59 (Greek: mykes – mushroom: logos – hyphae. Example: Fusarium study). P.A. Micheli is considered as founder of Mycology. Few renowned mycologists include Arthur H.R. Buller, John Webster, D.L.Hawksworth, G.C.Ainsworth, B.B.Mundkur, K.C.Mehta, C.V. Subramanian and T.S. Sadasivan.

Septate mycelium Coenocytic mycelium

Figure 1.19: Types of mycelium

E.J. Butler (1874-1943) • The mycelium is organised into loosely Father of Indian Mycology. He or compactly interwoven fungal tissues established Imperial Agricultural called plectenchyma. It is further Research Institute at Pusa, Bihar. It divided into two types prosenchyma was later shifted to New Delhi and at and pseudoparenchyma. In the former present known as Indian Agricultural type the hyphae are arranged loosely Research Insitute (IARI) He published but parallel to one another In the latter a book, ‘Fungi and Disease in Plants’ on hyphae are compactly arranged and Indian plant diseases in the year 1918. loose their identity. • In holocarpic forms the entire thallus 1.5.2 General characteristic features is converted into reproductive • Majority of fungi are made up of structure whereas in Eucarpic some thin, filamentous branched structures regions of the thallus are involved in called hyphae. A number of hyphae the reproduction other regions remain get interwoven to form mycelium. vegetative. Fungi reproduce both by The cell wall of fungi is made up of a asexual and sexual methods. The polysaccharide called chitin (polymer asexual phase is called Anamorph and of N-acetyl glucosamine). the sexual phase is called Teleomorph. • The fungal mycelium is categorised Fungi having both phases are called into two types based on the presence or Holomorph. absence of septa (Figure 1.19). In lower In general sexual reproduction in fungi fungi the is aseptate, multinucleate includes three steps 1. Fusion of two and is known as coenocytic mycelium protoplasts (plasmogamy) 2. Fusion of (Example: Albugo). In higher fungi a nuclei (karyogamy) and 3. Production of septum is present between the cells of the haploid spores through meiosis. Methods of

29

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 29 02-06-2018 13:43:59 reproduction in fungi is given in Figure 1.20 Mucor, Rhizopus). 1.5.3 Methods of Reproduction in Fungi 4. Spermatization: In this method a uninucleate pycniospore/microconidium Asexual Reproduction is transferred to receptive hyphal cell 1. Zoospores: They are flagellate structures (Example: Puccinia/Neurospora) produced in zoosporangia (Example: 5. Somatogamy: Fusion of two somatic Chytrids) cells of the hyphae (Example: Agaricus) 2. Conidia: The spores produced on Nucleus condiophores (Example: Aspergillus) 3. Oidia/Thallospores/Arthrospores: The hypha divide and develop in to spores called oidia (Example: Erysiphe). 4. Fission: The vegetative cell divide into 2 daughter cells. (Example: (a) Budding - Yeast Schizosaccharomyces-yeast). 5. Budding: A small outgrowth is developed on parent cell, which gets detached and become independent. (b) Fission - Yeast (Example: Saccharomyces-yeast) 6. : Thick walled resting spores are called

(Example: Fusarium). Sterigma Metula Sexual Reproduction Ramus 1. Planogametic copulation: Fusion of motile gamete is called planogametic Conidiophore copulation. a. Isogamy – Fusion of (c) Conidia formation - Penicillium morphologically and physiologicall similar gametes. (Example: Synchytrium). b. Anisogamy – Fusion of morphologically or physiologically dissimilar gametes (Example: Allomyces). c. Oogamy – Fusion of both morphologically and physiologically dissimilar gametes. (Example: Monoblepharis) 2. Gametangial contact: During sexual Chlamydospore reproduction a contact is established between antheridium and Oogonium (Example: Albugo) 3. Gametangial copulation: Fusion of (d) Thallospore - (e) Chlamydospore - gametangia to form (Example: 30 Erysiphe Fusarium

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 30 02-06-2018 13:43:59 Trichogyne

Microconidia

Archicarp (f) Sporangia - Mucor

‘+’ Strain ‘-’ Strain (i) Spermatisation - Neurospora

Progametangium Figure 1.20: Reproduction in Fungi

1.5.4 Classification of Fungi Many mycologists have attempted to classify fungi based on vegetative and Zygospore reproductive characters. Traditional classifications categorise fungi into 4 classes – Phycomycetes, Ascomycetes, Zygosporangium Basidiomycetes and Deuteromycetes. Among these ‘Phycomycetes’ include fungal species of Oomycetes, Chytridiomycetes and Zygomycetes which are considered as lower fungi indicating (g) Gametangial copulation - Rhizopus algal origin of fungi. Constantine J. Alexopoulos and Charles W. Mims in Antheridium the year 1979 proposed the classification of fungi in the book entitled ‘Introductory Mycology’. They classified fungi into three divisions namely Gymnomycota, Mastigomycota and Amastigomycota. There are 8 subdivisions, 11 classes, 1 form class and 3 form subclasses in the classification proposed by them. The salient features of some of the classes – Fertilization tube Oomycetes, Zygomycetes, Ascomycetes, Oogonium Basidiomycetes and Form class (h) Gametangial contact - Albugo Deuteromycetes are discussed below.

31

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 31 02-06-2018 13:44:01 Recently, with the advent of molecular methods myxomycetes and oomycetes were reclassified and treated under chromista. Oomycetes Coenocytic mycelium is present. The cell (b) wall is made up of Glucan and Cellulose. Zoospore with one whiplash and one Figure 1.21: Zygomycetes (a) Rhizopus tinsel flagellum is present. Sexual (b) Pilobolus reproduction is Oogamous. Example: • The mycelium is branched and Albugo coenocytic. Zygomycetes • Asexual reproduction by means of • Most of the species are saprophytic spores produced in sporangia. and live on decaying plant and animal • Sexual reproduction is by the fusion of matter in the soil. Some lead parasitic the gametangia which results in thick life (Example: Entomophthora on walled Zygospore. It remains dormant housefly) for long periods. The zygospore • Bread fungi (Example: Mucor, undergoes meiosis and produce spores. Rhizopus) and Coprophilous fungi Ascomycetes (Fungi growing on dung Example: Pilobolus) belong to this group • Ascomycetes include a wide range (Figure 1.21). of fungi such as , powdery mildews, cup fungi, morels and so on Sporangium Columella (Figure 1.22). Sporangiospore

Sporangiophore

(a) Morchella

Rhizoids

(a)

(b) Peziza

32

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 32 02-06-2018 13:44:04 • Although majority of the species live in terrestrial environment, some live in aquatic environments both fresh water and marine. • The mycelium is well developed, branched with simple septum. (c) Cleistothecium • Majority of them are saprophytes but few parasites are also known (Powdery Ostiole mildew – Erysiphe). • Asexual reproduction takes place by fission, budding, oidia, conidia, chlamydospore. Paraphysis • Sexual reproduction takes place by the fusion of two compatible nuclei. • Plasmogamy is not immediately (d) V.S. of Perithecium followed by karyogamy, instead a Ascus dikaryotic condition is prolonged for Paraphysis Ascospore several generations. • A special hyphae called ascogenous hyphae is formed. • A crozier is formed when the tip of the (e) V.S. of Apothecium ascogenous hyphae recurves forming a hooked cell. The two nuclei in the penultimate cell of the hypha fuse to form a diploid nucleus. This cell form young ascus. • The diploid nucleus undergo meiotic Ascospore division to produce four haploid nuclei, which further divide mitotically to form eight nuclei. The nucleus gets organised into 8 . • The ascospores are found inside a bag like structure called ascus. Due to the presence of ascus, this group is popularly called "Sac fungi". • Asci gets surrounded by sterile hyphae (f) Steps involved in the development of Ascus forming fruit body called . Figure 1.22: Structure and reproduction • There are 4 types of namely in Ascomycetes Cleistothecium (Completely closed),

33

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 33 02-06-2018 13:44:05 Perithecium (Flask shaped with • The mycelium is well developed, ostiole), Apothecium (Cup shaped, septate with dolipore septum(bracket open type) and Pseudothecium. like). Three types of mycelium namely Primary (Monokaryotic), Secondary Basidiomycetes (Dikaryotic) and tertiary are found. • Basidiomycetes include puff balls, • Clamp connections are formed to toad stools, Bird’s nest fungi, Bracket maintain dikaryotic condition. fungi, stink horns, rusts and smuts (Figure 1.23). • Asexual reproduction is by means of conidia, oidia or budding. • Sexual reproduction is present but sex organs are absent. Somatogamy or spermatisation results in plasmogamy. Karyogamy is delayed and dikaryotic phase is prolonged. (a) Agaricus (b) Geaster Karyogamy takes place in and it is immediately followed by meiotic division. • The four nuclei thus formed are transformed into which are borne on sterigmata outside the basidium (Exogenous ). The basidium is club shaped with four basidiospores, thus this group of fungi is popularly (c) Dolipore septum called “Club fungi”. The fruit body formed is called Basidiocarp.

Deuteromycetes or Fungi Imperfecti The fungi belonging to this group lack sexual reproduction and are called imperfect fungi. A large number of species live as saprophytes in soil and many are plant and animal parasites. Asexual Nucleus reproduction takes place by the production of conidia, chlamydospores, budding, (d) Clamp connection oidia etc., Conidia are also produced Figure 1.23: Structure and in special structures called Pycnidium, Reproduction in Basidiomycetes Acervulus, Sporodochium and Synnema (Figure 1.24). Parasexual cycle • The members are terrestrial and lead a operates in this group of fungi. This brings saprophytic and parasitic mode of life. genetic variation among the species.

34

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 34 02-06-2018 13:44:06 yeast. They deteriorate the timber. Fungi cause food poisoning due the production of toxins. The Beneficial and harmful activities of fungi are discussed below: Pycniospore Beneficial activities

Food Mushrooms like Lentinus edodes, Agaricus bisporus, Volvariella volvaceae are consumed for their high nutritive value. (a) Pycnidium - Phoma Yeasts provide vitamin B and Eremothecium

Conidium ashbyii is a rich source of Vitamin B12. Seta Conidiophore Medicine Fungi produce antibiotics which arrest the growth or destroy the bacteria. (b) Acervulus - Colletotrichum Some of the antibiotics produced by fungi include Penicillin (Penicillium notatum) Cephalosporins (Acremonium chrysogenum) Griseofulvin (Penicillium Conidia griseofulvum). Ergot alkaloids (Ergotamine) produced by Claviceps purpurea is used as vasoconstrictors. Industries Production of Organic acid: For the commercial production of organic acids fungi are employed in the Industries. Some of the organic acids and fungi which help in the production of organic acids are: Citric acid and Gluconic acid – Aspergillus (c) Synnemata - Graphium niger; Itaconic acid – Aspergillus terreus, Figure 1.24: Reproduction in Kojic acid – Aspergillus oryzae. Deuteromycetes Bakery and Brewery Yeast(Saccharomyces cerevisiae) is used for 1.5.5. Economic importance fermentation of sugars to yield alcohol. Fungi provide delicious and nutritious Bakeries utilize yeast for the production food called mushrooms. They recycle the of Bakery products like Bread, buns, minerals by decomposing the litter thus rolls etc., Penicillium roquefortii and adding fertility to the soil. Dairy industry Penicillium camemberti were employed in is based on a single celled fungus called cheese production.

35

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 35 02-06-2018 13:44:07 Production of enzymes plant growth and is used as growth Aspergillus oryzae, Aspergillus niger were promoter. employed in the production of enzymes Harmful activities like Amylase, Protease, Lactase etc., Fungi like Amanita phalloides, Amanita ’Rennet’ which helps in the coagulation of verna, Boletus satanus are highly poisonous milk in cheese manufacturing is derived due to the production of Toxins. These fungi from Mucor spp. are commonly referred as “Toad stools”. Agriculture Aspergillus, Rhizopus, Mucor and Mycorrhiza forming fungi like Penicilium are involved in spoilage of food Rhizoctonia, Phallus, Scleroderma helps in materials. Aspergillus flavus infest dried absorption of water and minerals. foods and produce carcinogenic toxin Fungi like Beauveria bassiana, called aflatoxin. Metarhizium anisopliae are used as Patulin, ochratoxin A are some of the Biopesticides to eradicate the pests of crops. toxins produced by fungi. Gibberellin, produced by a fungus Fungi cause diseases in Human beings Gibberella fujikuroi induce the and Plants (Table 1.11 and Figure 1.25)

(a) of wheat (b) Anthracnose of beans Puccinia graminis var tritici Colletotrichum lindemuthianum. Figure 1.25: Fungal disease in plants.

Table 1.11: Diseases caused by fungi S. No Name of the disease Causal organism Plant diseases 1. Blast of Paddy Magnaporthe grisea 2. Red rot of sugarcane Colletotrichum falcatum 3. Anthracnose of Beans Colletotrichum lindemuthianum 4. White rust of crucifers Albugo candida 5. Peach leaf curl Taphrina deformans 6. Rust of wheat Puccinia graminis tritici Human diseases 1. Athlete’s foot Epidermophyton floccosum 2. Candidiasis Candida albicans 3. Coccidioidomycosis Coccidioides immitis 4. Aspergillosis Aspergillus fumigatus

36

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 36 02-06-2018 13:44:07 Activity 1.4 place it on a slide and stain the mycelium Get a button mushroom. Draw diagram using lactophenol cotton blue. Observe of the fruit body. Take a thin longitudinal the mycelium and sporangium under the section passing through the gill and microscope and Record your observation observe the section under a microscope. and identify the fungi and its group based Record your observations. on characteristic features. 1.5.6 Mycorrhizae Dermatophytes are fungi which cause infec- The Symbiotic association between fungal tion in skin. Exa­ mple: mycelium and roots of plants is called as Trichophyton, Tinea, mycorrhizae. In this relationship fungi Microsporum and Epidermophyton absorbs nutrition from the root and in turn the hyphal network of mycorrhizae forming The late blight disease of Potato by fungi helps the plant to absorb water and Phytophthora infestans caused a million mineral nutrients from the soil (Figure 1.26) deaths, and drove more to emigrate Mycorrhizae are classified into three types from Ireland (1843-1845). In India Helminthosporium oryzae, Blight of Importance of Mycorrhizae Paddy is also a factor for Bengal famine • Helps to derive nutrition in Monotropa, in 1942-1943 a saprophytic angiosperm, • Improves the availability of minerals Activity 1.5 and water to the plants. Keep a slice of bread in a clean plastic tray • Provides drought resistance to the or plate. Wet the surface with little water. plants Leave the setup for 3 or 4 days. Observe the mouldy growth on the surface of the bread. • Protects roots of higher plants from Using a needle remove some mycelium and the attack of plant pathogens

Mycorrhizae Ectomycorrhizae Endomycorrhizae Ectendomycorrhizae The fungal myceli- The hyphae grows mainly inside the roots, The fungi form both um forms a dense penetrate the outer cortical cells of the plant mantle and also pen- sheath around the root. A small portion of the mycelium is etrates the cortical root called mantle. found outside the root. This form is also called cells. The hyphal net- Vesicular Arbuscular Mycorrhizal fungi (VAM work penetrate the Fungi) due to the presence of Vesicle or arbuscle intercellular spac- like haustoria. es of the epidermis 1. Arbuscular mycorrhizae(VAM) and cortex to form Example: Gigaspora Hartignet. Exam- 2. Ericoid mycorrhizae-Example: Oidiodendron ple: Pisolithus tinc- 3. Orchid mycorrhizae -Example: Rhizoctonia torius.

37

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 37 02-06-2018 13:44:08 like (Figure 1.27). • The distribution of algal cells distinguishes lichens into two forms namely Homoiomerous (Algal cells evenly distributed in the thallus) and Vesicle Heteromerous (a distinct layer of Fungal sheath algae and fungi present) Epiblema Cortex Arbuscle Mycelium • If the fungal partner of lichen belongs

Endomycorrhizae Ectomycorrhizae to ascomycetes, it is called Ascolichen and if it is basidiomycetes it is called Figure 1.26: T.S. of root showing Basidiolichen. mycorrhizae 1.5.7 Lichens The symbiotic association between algae and fungi is called lichens. The algal partner is called Phycobiont or Photobiont and the fungal partner is called Mycobiont. Algae provide nutrition for fungal partner in turn fungi provide protection and also help to (a) Crustose lichen fix the thallus to the substratum through rhizinae. Asexual reproduction takes place through fragmentation, Soredia and Isidia. Phycobionts reproduce by akinetes, hormogonia, aplanospore etc., Mycobionts undergo sexual reproduction and produce ascocarps. Classification (b) Foliose Lichen • Based on the habitat lichens are classified into following types: Corticolous( on Bark) Lignicolous(on Wood) Saxicolous(on rocks) Terricolous(on ground) Marine(on siliceous rocks of sea) Fresh water(on siliceous rock of fresh water). • On the basis of morphology of the thallus they are divided into Leprose (c) Fruticose Lichen (a distinct fungal layer is absent) Crustose-crust like; Foliose-leaf like; Figure 1.27: Types of Lichens Fruticose- branched pendulous shrub

38

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 38 02-06-2018 13:44:15 Lichens secrete organic acids like Oxalic prokaryotic and are adapted to thrive in acids which corrodes the rock surface and extreme environments. Cyanobacteeria are helps in weathering of rocks, thus acting as prokaryotic organisms and are also called pioneers in Xerosere. Usnic acid produced Blue Green Algae. The members of this from lichens show antibiotic properties. group are ensheathed by mucilage cover. Lichens are sensitive to air pollutants They reproduce by vegetative and asexual especially to sulphur-di-oxide. Therefore, methods. they are considered as pollution indicators. Fungi are Eukaryotic, heterotrophic, The dye present in litmus paper used as unicellular or multicellular organisms. acid base indicator in the laboratories is The cell wall is made up of chitin. obtained from Roccella montagnei. Cladonia They reproduce asexually by rangiferina (Reindeer moss) is used as food producing sporangiospores, conidia, for animals living in Tundra regions. Thallospores, chlamydospores etc., The sexual reproduction is isogamous, Summary ansiogamous and oogamous. In addition, Earth is endowed with living and gametic copulation, gametic fusion, nonliving things. The attributes of living spermatisation are also found. They things include growth, metabolism, are beneficial to mankind. Some are Reproduction, Irritability and so on. known to cause disease in plants and Viruses are considered as Biological human beings. The symbiotic association puzzle and exhibit both living and non between the roots of higher plants and living characteristic features. They are fungal mycelium is called mycorrhizae. ultramicroscopic, obligate parasites and Lichen thallus includes both phycobiont cause disease in plants and animals. They and mycobiont. It is an example for multiply by lytic and lysogenic cycle. Five symbiotic association. Kingdom classification was proposed by Whittaker, which include Monera, Evaluation Protista, Fungi, Plantae and Animalia. 1. Which one of the Carl woese divided the living world into 3 following statement domains- Bacteria, Archaeae and Eukarya. about virus is correct The domain Eukarya include Plantae, a. Possess their own Animalia and Fungi. A new Kingdom called metabolic system Chromista was erected to include Diatoms, b. They are facultative parasites Cryptomonads and Oomycetes. Bacteria are microscopic, prokaryotic organisms c. They contain DNA or RNA and possess peptidoglycan in their cell d. Enzymes are present wall. Based on Gram Staining method they 2. Identify the incorrect statement about are classified into Gram positive and Gram the Gram positive bacteria negative type. They reproduce asexually by a. Teichoic acid absent Binary fission. Sexual reproduction occurs b. High percentage of peptidoglycan through Conjugation, Transformation is found in cell wall and Transduction. Archaebacteria are

39

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 39 02-06-2018 13:44:15 c. Cell wall is single layered 5. Identify the correctly matched pair d. Lipopolysaccharide is present in a. Actinomycete – a) Late blight cell wall b. Mycoplasma – b) lumpy jaw 3. Identify the Archaebacterium c. Bacteria – c) Crown gall a. Acetobacter d. Fungi – d) sandal spike b. Erwinia 6. Differentiate Homoiomerous and c. Treponema Heteromerous lichens. d. Methanobacterium 7. Write the distinguishing features of 4. The correct statement regarding Blue Monera. green algae is 8. Why do farmers plant leguminous a. lack of motile structures crops in crop rotations/mixed b. presence of cellulose in cell wall cropping? c. absence of mucilage around the 9. Briefly discuss on five kingdom thallus classification. Add a note on merits and demerits. d. Presence of floridean starch 10. Give a general account on lichens.

40

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 40 02-06-2018 13:44:15 ICT Corner

Bacteria

Let’s explore the structure and shapes of Bacteria.

Steps

• Scan the QR code or go to google play store and type bacteria interactive educational VR 3D • Download the app and install it • Follow the above steps and explore the interactives of each part and its functions.

Activity

• Select structure tap and note the internal structure of bacteria • Click cell wall and note the difference between different shapes

Step 2 Step 3

Step 1 Step 4 Step 5

URL:

https://play.google.com/store/apps/details?id=com.rendernet.bacteria&hl=en Alternate web: https://play.google.com/store/apps/details?id=com.rendernet.bacteria&hl=en

* Pictures are indicative only

41

TN_GOVT_BOTANY_XI_Page 001-041 CH01.indd 41 02-06-2018 13:44:17