University of Kirkuk/College of nursing /Microbiology Introduction of microbiology, and bacterial structure 1 Dr. Gulbahar F. Karim …………………………………………………………………………………………………………………………………..
Lec.1// Introduction of microbiology, and bacterial structure Microbiology: is the science that deal with the study of microorganisms. Microorganisms can be found in every ecosystem, and in close association with every type of multicellular organisms. They populate the healthy human body by billions as normal flora. -Many scientist had rule in the development of this science including: -Louis Pasteur (1857) established that fermentation was the result of microbial activity. -Robert Koch (father of bacteriology) perfected bacteriological techniques during his studies on the culture of Bacillus anthraces (1876). He introduced staining techniques and also methods of obtaining bacteria in pure culture using solid media. He discovered Mycobacterium tuberculosis (1882), Vibrio cholerae (1883) -Fleming (1925) made the accidental discovery that the fungus penicillium produces a substance which destroys staphylococci. -Microbiology include many branches. Here we are concerned with medical microbiology. Medical microbiology (Gr. mikros-small, bios-life, logos-science) is the study of causative agents of infectious disease of human beings and their reactions to such infections. In other words it deals with etiology, pathogenesis, laboratory diagnosis, treatment, epidemiology and control of infection. It is studied under following headings: a. Parasitology ,Mycology , Immunology , Bacteriology, Genetics , and and Virology (which are consider between living and non living organisms). Microorganisms are classified under the kingdom Protista which is subdivided into two groups: 1-Eukaryotic organisms(with nucleus): include fungi, Algae, protozoa, helminthes. 2-Prokaryotic organisms(without nucleus): include bacteria and green algae. Morphology of bacteria: - Bacteria are unicellular,free living organisms ,live everywhere, present in soil, water. Most of them are saprophytic (live on dead organic material),they are capable of performing all essential processes of life (e.g. growth, metabolism, and reproduction). Very small in size and vary in shape.
University of Kirkuk/College of nursing /Microbiology Introduction of microbiology, and bacterial structure 2 Dr. Gulbahar F. Karim …………………………………………………………………………………………………………………………………..
The differences between Prokaryotes and Eukaryotes cells :
Character Prokaryotes Eukaryotes Nucleus:- Nuclear membrane Absent Present Nucleolous Absent Present Deoxiribonucleoprotein(hixon) Absent Present Chromosome Single (circular) multiple Mitotic division Absent Present
Cytoplasm organelles: Mitochondria Absent Present Lysosomes Absent Present Golgi apparatus Absent Present Endoplasmic reticulum Absent Present
Plasma membrane Sterols Absent Present Mesosome Present Absent Cell wall: Present Present in plant cell
Cell wall peptidoglycan Present (in many Absent bacteria) Reproduction Binary fission Sexual and asexual Respiration Via cytoplasmic via mitochondria membrane Size of bacteria: -Most bacteria are small, their size is measured in terms of micron (micrometer). 1 micron(µ), or micrometer(µm) = one thousand of millimeter (1µ= 10-3 mm). Generally cocci is about 1 µm in diameter, and bacilli are about 2-10 µm in length , and 0.2-0.5µm in width. Shape of bacteria: Bacteria are classified as: 1- Cocci (from kokkos, meaning spherical). It is arranged in : a- Cluster: (Grape like cluster) e.g: Staphylococci. b- Chain: e.g: Streptococci. c- Pair: e.g: diplococcic e.g: Streptococcus pneumoniae d- Tetrad: Group of four: e.g: Micrococci e- Group of eight: e.g: Sarcina
University of Kirkuk/College of nursing /Microbiology Introduction of microbiology, and bacterial structure 3 Dr. Gulbahar F. Karim …………………………………………………………………………………………………………………………………..
Bacilli (meaning rod): May be arranged as: a- Chinese letter arangment: e.g: Corynebacteria. ٬ ٬ ٬ b- Vibrio: they are comma shaped curved rod e.g: Vibrio cholerae c- Spirochaetes coiled, e.g: Treponema pallidum d- branched to filamentous: e.g: Actynomyces, nocardia
Cell wall: -Composed of peptidoglycan (mucopeptide,murein), responsible of structural integrity and shape of bacteria. Cell wall Antigen of gram negative bacteria act as endotoxin (lipopoly saccaride LPS ). A coparison of cell wall of gram positive and gram negative bacteria: Characteristic of cell wall Gram positive bacteria Gram negative bacteria Thickness 15-23 nm 10-15 nm Variety of amino acid Few several Aromatic and sulfur Absent Present containing amino acid Lipids Low 2-4 % High 15-20 % Teichoic acid present Absent
University of Kirkuk/College of nursing /Microbiology Introduction of microbiology, and bacterial structure 4 Dr. Gulbahar F. Karim …………………………………………………………………………………………………………………………………..
Figure: Differences of cell wall between gram positive and gram negative bacteria Function of cell wall: 1- Protection of internal structure, and resistant to harmful effect of environment 2- Give shape to the cell. 3- Confers rigidity and ductility. 4- Role in division of bacteria. 5- Antigenic determinants. Cytoplasmic membrane: It is thin semi permeable membrane, which lies under the cell wall. It is 5-10nm in width. It composed of bilipid layer (phospholipid) and protein . Function: 1- the membrane is selesctive in permeability(semi permeable), controlling the kind and amount of molecules that enter and leave the cell. 2- Enzyme biosynthesis activity. 3- An in fold outer membrane (mesosome) for respiration. Mesosome: They are vesicular convoluted structure formed as imagination of plasma membrane in to the cytoplasm. They are more prominent in gram positive bacteria. Function of mesosome: 1- They are the site of respiratory enzymes in bacteria. 2- Coordinate nuclear and cytoplasmic division during binary fission. University of Kirkuk/College of nursing /Microbiology Introduction of microbiology, and bacterial structure 5 Dr. Gulbahar F. Karim …………………………………………………………………………………………………………………………………..
Figure: The ultra structure of bacteria Cytoplasm: The bacterial cytoplasm composed of organic and in organic solutes in viscous watery solution. Ribosome: These are complex globular structure compsed of ribonucleoprotein granules . Function of ribosomes: They are the side of protein synthesis.
Nucleus: It is a haploid stranded circular closed DNA molecule tightly coiled inside the cytoplasm in many bacteria. A small portion of DNA persist as plasmid. The bacterial nucleus is not surrounded by nuclear membrane. They do not have nucleolus.
Spore: are round or oval produce by some gram positive bacteria under unsuitable environment(such as nutrition deprivation), which result in formation of dormant cell inside cell called endospore, that can released from original cell as free spore. Spores are the most resistant life-forms known.
University of Kirkuk/College of nursing /Microbiology Introduction of microbiology, and bacterial structure 6 Dr. Gulbahar F. Karim …………………………………………………………………………………………………………………………………..
Capsule: is a loose layer around cell wall, found in some bacteria (gram-positive and negative). Visualized by india ink stain. Function: 1- Protect bacteria from deleterious agents e.g: lytic enzymes. 2- Contribute to the virulence of pathogenic bacteria by inhibiting phagocytosis Flagella: Are long contractile filamentous appendage, originated from cell membrane, and they are organ of motility in some bacteria. The types of flagella arrangement are: 1- Monotrichate: one flagellum at one pole of organism. 2- Amphitrichate: one flagellum at both the poles. 3- Lophotrichate: A tuft of flagella at the end. 4- Peritrichate: several flagella present all over the surface of bacteria.
Function: 1- Bacterial motility. 2- Facilitate movment to word food(chemotaxis). 3- Express antigenic determinants that distinguish strain of organisms. Fimbriae (Pilli): are a hair like structures composed of protein sub units (pilin). Function: 1- Adhesion: promote adherence of bacterium to the host. 2- Sex-pili (F-pili ) promote the transfer of segments of bacterial chromosomes from bacterium to another bacterium.