MYCOPLASMA OR PPLO’S

• Genus of bacteria, smallest, wall-less free living prokayotes belonging to class-Mollicutes. • lacks cell wall, so resistant to antibiotics which target the cell wall. • They cause various diseases in humans like various respiratory diseases and pelvic inflammatory disorders • first discovered by Pasteur in 1843 when he was studying the causal organisms of pleuropneumonia in catties. • He named it as Pleuropneumonia like organisms (PPLO • first isolated by two French bacteriologists E. Nocard and E.R. Roux in 1898 from pleural fluids of catties affected with pleuropneumonia and these organisms were named as Mycoplasma in 1929 by Nowar. Mycoplasma • highly pleomorphic, • reproduce by budding and/or by fission and by producing small bodies. • They lack sterols but are capable of incorporating exogenous sterols obtained from growth medium. Habit and Habitat of Mycoplasma:

• Mycoplasmas are parasitic as well as saprophytic. • More than 200 mycoplasma like bodies are found to be associated with sewage, plants, animals, insects, humus, hot water springs and other high temperature environment. • They have been found in phloem tissues of diseased plants. • M. orale and M. salivarium are found almost in every healthy adult. • M. hominis is present in a large proportion in sexually active adults. • Diseases like primary atypical pneumonia (PAP) in the mouth, pharynx and genito-urinary tract and tonsillitis in humans are caused by mycoplasma. Structure of Mycoplasma Cell Structure of Mycoplasma:

• In mycoplasma, the cells are small varying from 300 nm to 800 nm in diameter. • Rigid cell wall is absent. • Cells are surrounded by a triple layered lipo- proteinaceous unit membrane. • It is about 10 nm thick. Unit membrane encloses the cytoplasm. • Within the cytoplasm RNA (ribosomes) and DNA are present. • The ribosomes are 14 nm in diameter and 72 S type. • DNA is double stranded helix. • It can be distinguished from bacterial DNA by its low guanine and cytosine content. • The DNA is up to four percent and RNA is about eight percent and it is less than half that usually occurs in other protoplasm’s. • The guanine and cytosine (G and C).Contents in DNA range from 23- 46 percent. • In some species e.g., M. gallisepticum some polar bodies protrude out from one or the other end of the cell. • These are called bleb and are considered to be the site of enzymatic activities and attachment during infection. • Possess a replicating disc at one end which assist replication process and also the separation of the genetic materials. • Most mycoplasma require a rich nutrient medium containing sterols and serum protein for growth. On solid (Agar) medium mycoplasmas form minute, transparent colonies that typically have a characteristic “fried egg” appearance. Reproduction in mycoplasma

• Mycoplasmas are highly pleomorphic, reproduce by budding and/or by fission and by producing small bodies. Schematic presentation of the mode of mycoplasma reproduction. Cells may either divide by binary fission or first elongate to multinucleate filaments, which subsequently breakup to coccoid bodies. General Characters of Mycoplasma:

• They are unicellular, smallest, non-motile and prokaryotic organisms forming fried egg shaped colonies • pleomorphic i.e., able to change about 10 nm thick. their shape depending upon • Within the cytoplasm ribosomes culture media- rod like, ring like, are found scattered in the globoid or filamentous. peripheral zone. These are 14 nm • The filaments are of uniform in diameter and resemble with diameter (100-300 nm) and vary in bacteria in sedimentation length from 3 nm to 150 nm. characteristic of both the • Some mycoplasma predominantly nucleoprotein and nucleic acid. assume spherical shape (300-800 • The ribosomes are 72S type. nm in diameter). • Within the cytoplasm fine fibrillar • They are ultra-filterable i.e., they DNA is present. It is double can pass through bacteria-proof stranded helix. filters. • They do not possess rigid cell wall. • The cells are delimited by soft tripple layered lipo-proteinaceous membrane. It is unit membrane • Mycoplasma generally grow more slowly than bacteria. • They are also killed by temperature of 40-55°C in fifteen minutes. • They do not produce spores. • Like other prokaryotes, they usually divide by binary fission. • They have Heterotrophic nutrition. Some live as saprophytes but the majority are parasites of plants and animals. • The parasitic nature is due to the inability of mycoplasmal bacteria to synthesise the required growth factor. • The Fungi • Protista – The Protozoa • They are eukaryotic, spore bearing, achlorophyllous microorganism. • Study of Fungi is Mycology. • Fungi is a eukaryotic organism that includes microorganisms such as yeasts, moulds, and mushrooms. These organisms are classified under kingdom fungi also called as Myceteae • The organisms found in Kingdom fungi contain a cell wall and are omnipresent. • They are classified as heterotrophs among the living organisms and live as saprophytes, parasites, Symbionts. • Almost all the fungi have a filamentous structure except yeast the cells. • They can be either single-celled or multicellular organism. • Fungi consist of long thread-like structures known as hyphae. These hyphae together form a mesh-like structure called mycelium. • Fungi possess a cell wall which is made up of chitin and polysaccharides. • The cell wall comprises of protoplast which is differentiated into other cell parts such as cell membrane, cytoplasm, cell organelles and nuclei. • The nucleus is dense, clear, with chromatin threads. The nucleus is surrounded by a nuclear membrane. • Fungi are eukaryotic, non-vascular, non-motile and heterotrophic organisms. • They may be unicellular or filamentous. • They reproduce by means of spores. • Fungi exhibit the phenomenon of alternation of generation. • Fungi lack chlorophyll and hence cannot perform photosynthesis. • Fungi store their food in the form of starch. • Biosynthesis of chitin occurs in fungi. • The nuclei of the fungi are very small. • During mitosis, the nuclear envelope is not dissolved. • The fungi have no embryonic stage. They develop from the spores. • The mode of reproduction is sexual or asexual. • Some fungi are parasitic and can infect the host. • Fungi produce a chemical called pheromone which leads to sexual reproduction in fungi. For eg., mushrooms, moulds, yeast. • Kingdom Fungi is classified based on different modes. • The different classification of fungi are as follows: • On the basis of nutrition, kingdom fungi can be classified into following groups. • Saprophytic – The fungi obtain their nutrition by feeding on dead organic substances. Examples: Rhizopus, Penicillium, and Aspergillus. • Parasitic – The fungi obtain their nutrition by living on other living organisms (plants or animals) and absorb nutrients from their host. Examples: Taphrina, and Puccinia. • Symbiotic – These fungi live by having an interdependent relationship association with other species in which both are mutually benefited. Examples: Lichens and mycorrhiza. Lichens are the symbiotic association between algae and fungi. Here both algae and fungi are mutually benefited as fungi provide shelter for algae and in reverse algae synthesis carbohydrates for fungi. • Phycomycetes: They are fungi with an decomposers, parasitic or saprophytic. unicellular, non-septate mycelium (500 The sexual spores are called ascospores. species). The spores (endospores) are Asexual reproduction occurs by enclosed in special sporangia. conidiospores. Example – Reproduction is sexual and asexual. Saccharomyces Atypical representative of Mucor (bread • Basidiomycetes – Mushrooms are the mould) is Mucor mucedo. Pathogenic most commonly found basidiomycetes species of this Mucor (mould) may and mostly live as parasites. Sexual cause infection of lungs, middle ear and reproduction occurs by basidiospores. general severe infectious process in Asexual reproduction occurs by conidia, man. budding or fragmentation. Example- • Zygomycetes – These are formed by the Agaricus fusion of two different cells. The sexual • Deuteromycetes – They are otherwise spores are known as zygospores while called imperfect fungi as they do not the asexual spores are known as follow the regular reproduction cycle as sporangiospores. The hyphae are the other fungi. They do not reproduce without the septa. sexually. Asexual reproduction occurs by • Ascomycetes – They are also called as conidia. Example – Trichoderma. sac fungi. They can be coprophilous,

: male and female reproductive structures are present in the same plant or fungal mycelium : an organ or cell in which gametes are produced that is found in many multicellular protists, algae, fungi, and the gametophytes of plants : a reproductive particle, usually a single cell, released by a fungus, alga, or plant that may germinate into another : a case, capsule, or container in which spores are produced by an organism : the fusion of two nuclei within a cell : stage of sexual reproduction joining the cytoplasm of two parent mycelia without the fusion of nuclei • Reproduction in fungi is both by sexual and asexual means. The sexual mode of reproduction is referred to as and the asexual mode of reproduction is referred to as . – By budding, fission, and fragmentation – This takes place with the help of spores called conidia or zoospores or sporangiospores – ascospores, basidiospores, and oospores – The conventional mode of sexual reproduction is not always observed in the kingdom Fungi. In some fungi, the fusion of two haploid hyphae does not result in the formation of a diploid cell. In such cases, there appears an intermediate stage called the dikaryophase. This stage is followed by the formation of diploid cells. • Fungi reproduce asexually by , or producing . Fragments of hyphae can grow new colonies. Mycelial fragmentation occurs when a fungal mycelium separates into pieces with each component growing into a separate mycelium. Somatic cells in yeast form buds. During budding (a type of cytokinesis), a bulge forms on the side of the cell, the nucleus divides mitotically, and the bud ultimately detaches itself from the mother cell. • The most common mode of asexual reproduction is through the formation of asexual spores, which are produced by one parent only (through mitosis) and are genetically identical to that parent. Spores allow fungi to expand their distribution and colonize new environments. They may be released from the parent thallus, either outside or within a special reproductive sac called a sporangium.

• There are many types of asexual spores. are unicellular or multicellular spores that are released directly from the tip or side of the hypha. Other asexual spores originate in the fragmentation of a hypha to form single cells that are released as spores; some of these have a thick wall surrounding the fragment. Yet others bud off the vegetative parent cell. Sporangiospores are produced in a sporangium. Sexual Reproduction

• Sexual reproduction introduces genetic variation into a population of fungi. • In fungi, sexual reproduction often occurs in response to adverse environmental conditions. • Two mating types are produced. When both mating types are present in the same mycelium, it is called homothallic, or self-fertile. Heterothallic mycelia require two different, but compatible, mycelia to reproduce sexually. • Although there are many variations in fungal sexual reproduction, all include the following three stages. – First, during (union of cytoplasm”), two haploid cells fuse, leading to a dikaryotic stage where two haploid nuclei coexist in a single cell. – During (“nuclear marriage”), the haploid nuclei fuse to form a diploid zygote nucleus. – Finally, takes place in the gametangia (singular, gametangium) organs, in which gametes of different mating types are generated. At this stage, spores are disseminated into the environment. • Plasmogamy and karyogamy may occur in a number of different ways in different taxonomic groups of fungi as described below: • (a) Gametic union: – In lower fungi, such as chytrids, sexual reproduction takes place by fusion of male and female gametes. The male and female gametes may be morphologically similar (isogamy) or dissimilar (anisogamy). One or both gametes may be motile or non-motile (aplanogamy). • (b) Gametangial contact: – In many phycomycetes, such as Saprolegnia, sexual reproduction is effected by gametangial contact. A gametangium is the structure in which gametes are formed. The male and female gametangia come in contact and a pore is produced at the point of contact. The male gametes (nuclei) pass through the pore into the female gametangium where they fertilize the eggs or oospheres to produce diploid oospores. • (c) Gametangial copulation: • In the zygomycetes, such as Mucor, the male and female gametangia come in contact and the entire gametangia fuse with other. Thereby, their separate identity is lost and the fusion produces a zygospore. In the zygospore, the male and female nuclei pair with each other. Eventually, some of these pairs of nuclei fuse and the diploid nuclei undergo meiosis to restore haploidy. • (d) Spermatization: • In some basidiomycetes, such as the rust-fungus Puccinia, the male gametes are called spermatia which are produced in pycnidia (or spermogonia). The uninucleate non-motile spermatia are passively transferred by insects to the receptive female hyphae leading to plasmogamy. The male nucleus passes into the female receptive hypha and fuse with a female nucleus. • (e) Somatogamy: • In higher basidiomycetes, like mushrooms, specialized sex organs are totally absent. In these fungi, male and female nuclei are brought together by fusion of vegetative hyphae originating from mycelia of opposite mating types

Examples of Fungi

• Following are the common examples of fungi: • Yeast • Mushrooms • Moulds • Truffles Uses of Fungi Following are some of the important uses of fungi: 1. Recycling – They play a major role in recycling the dead and decayed matter. 2. Food – Mushrooms species are edible which are cultured and are used as food by humans. 3. Medicines – There are many fungi which are used to produce antibiotics, which are used to control diseases in humans and animals. Penicillin antibiotic is derived from a common fungi Penicillium. 4. Biocontrol Agents – Fungi are involved in exploiting insects, other small worms and help in controlling pests. Spores of fungi are used as spray-on crops. 5. Food spoilage – Fungi play a major role in recycling organic material and are also responsible for major spoilage and economic losses of stored food. Kingdom Protista • They are unicellular and eukaryotic organisms. • Some of them have cilia or flagella for mobility. • Sexual reproduction is by a process of cell fusion and zygote formation. • Kingdom Protista is categorized into subsequent groups: 1. Chrysophytes: The golden algae (desmids) and diatoms fall under this group. They are found in marine and freshwater habitats. 2. Dinoflagellates: They are usually photosynthetic and marine. The colour they appear is dependent on the key pigments in their cells; they appear red, blue, brown, green or yellow. 3. Euglenoids: Most of them live in freshwater habitation in motionless water. The cell wall is absent in them, instead, there is a protein-rich layer called pellicle. 4. Slime Moulds: These are saprophytic. The body moves along putrefying leaves and twigs and nourishes itself on organic material. Under favourable surroundings, they form an accumulation and were called Plasmodial slime moulds. 5. Protozoans: They are heterotrophs and survive either as parasites or predators.

Protista are simple eukaryotic organisms that are neither animals, plants nor fungi. Protists are unicellular in nature, or they can be found as a colony of cells. Most protists live in water, damp terrestrial environments, or even as parasites. Characteristics of Kingdom Protista • Membrane enclosed nucleus • These are usually aquatic, present in the soil or in areas with moisture. • Most protist species are unicellular organisms, few are multicellular protists such as kelp. Some species of kelp grow so large that they exceed over 100 feet in height. (Giant Kelp). • the cells of these species have a nucleus which is bound by organelles. • They may be autotrophic or heterotrophic in nature. • Symbiosis is observed in the members of this class. For instance, kelp (seaweed) is a multicellular protist that provides otters protection from predators amidst its thick kelp. In turn, the otters eat sea urchins that tend to feed on kelp. • Parasitism is also observed in protists. Species such as Trypanosoma protozoa can cause sleeping sickness in humans. • Protists exhibit locomotion through cilia and flagella. A few organisms belonging to kingdom Protista have pseudopodia that help them to move. • Protista reproduces by asexual means. The sexual method of reproduction is extremely rare and occurs only during times of stress. Grouping of Unicellular Protista

• We can classify unicellular protists into three major groups: – Photosynthetic Protists. • Example: Dinoflagellates, Diatoms, Euglenoids – Consumer Protists. • Example: Slime moulds or Myxomycetes – Protozoan Protists. • Example: Zooflagellate, Sarcodina, Sporozoa, Ciliata

Chrysophytes

Protozoans Dianoflagellates

Major Classification of protist

Slime Moulds Euglenoids • Chrysophytes • This group comprises of the diatoms and golden algae (desmids). We find them in fresh water as well as in marine environments. They are microscopic. These organisms float passively in water currents (plankton). • Dianoflagellates • These organisms are usually marine and photosynthetic. They have an appearance of various colours like yellow, green, brown, blue or red. Their colour is influenced and decided by the main pigments present in their cells. The cell wall has stiff cellulose plates on its outer surface. These organisms usually have two flagella; one lies longitudinally and the other transversely in a furrow between the wall plates. Euglenoids • These are mostly freshwater organisms. We can find them in stagnant water. They do not have a cell wall. Rather, they are built with a protein- rich layer, pellicle that makes their body flexible. They have two flagella. One is short and the other is a long one. The two flagella join with each other at a swelling called paraflagellar body. • Euglena is a connecting link between animals and plants. Nutrition in Euglena is mixotrophic, when the light is available it is photosynthetic, in darkness, it is saprophytic absorbing food from surrounding water. Slime Moulds • Slime moulds are saprophytic protists. Their body is capable of moving through decaying twigs and leaves engulfing organic material. Under suitable conditions, they form an aggregation called Plasmodium which may grow and spread over several feet. During unfavourable conditions, the plasmodium differentiates and forms fruiting bodies bearing spores at their tips. • The spores possess true walls. The spores are dispersed by air currents. They are extremely resistant to changes in the atmosphere. They are capable of surviving for many years, even under adverse conditions. • Slime Moulds • Slime moulds are saprophytic protists. Their body is capable of moving through decaying twigs and leaves engulfing organic material. Under suitable conditions, they form an aggregation called Plasmodium which may grow and spread over several feet. During unfavourable conditions, the plasmodium differentiates and forms fruiting bodies bearing spores at their tips. • The spores possess true walls. The spores are dispersed by air currents. They are extremely resistant to changes in the atmosphere. They are capable of surviving for many years, even under adverse conditions. Protozoans • All protozoans are heterotrophs and live as predators or parasites. They are believed to be primitive relatives of animals. There are four major groups of protozoan: • Flagellated Protozoans: They possess flagella for locomotion. They may be free-living aquatics, parasites, commensals or symbionts. Zooflagellates are generally uninucleate, occasionally multinucleate. • Amoebid Protozoans: They develop pseudopodia which are temporary protoplasmic outgrowths. These are used for locomotion and engulfing food articles. Sarcodines are mostly free-living, found in fresh water, sea water and on damp soil. • Sporozoans: All sporozoans are endoparasites. Some sporozoans such as Eimeria cause severe diseases like coccidiosis in the birds. Nutrition is parasitic (absorptive). Phagotrophy is rare. • Ciliated Protozoans: Ciliates are protozoan protists. These develop a number of cilia during a part or whole of the life cycle. They use cilia for locomotion and driving food. There is a high degree of morphological and physiological specialisation. There are definite regions for ingestion and egestion. The region of ingestion consists of an oral groove, cytostome (mouth) and gullet.