Morphology of bacteria

For DMLT, BMLT, and MBBS students

1. MORPHOLOGY AND CLASSIFICATION Arun Kumar

2. Introduction : Medical Microbiology – Branch of medicine that deals with the study of Microorganisms and their role in human health and diseases (Diagnosis, treatment and Prevention). Branches – General Microbiology Immunology Bacteriology Virology Mycology Prasitology .

3. Important Pioneers 1 . Louis Pasteur: Father of Modern Microbiology Proposed principles of Fermentation Introduced sterilization techniques Described- Pasteurization of milk Vaccine development – Anthrax, Fowl Cholera, and Rabies. Postulated – Germ Theory of disease . Identified silk worm disease

4. 2. Robert Koch: Introduced Solid Media Introduced methods for isolation of bacteria. Discovered Anthrax bacilli, Tubercule bacilli, and cholera bacilli. Koch Posulate : Four criteria to identify the causative agent of a particular disease, these include: The microorganism or other pathogen must be present in all cases of the disease The pathogen can be isolated from the diseased host and grown in pure culture The pathogen from the pure culture must cause the disease when inoculated into a healthy, susceptible laboratory animal 4. The pathogen must be reisolated from the new host and shown to be the same as the originally inoculated pathogen.

5. Classification : hierarchy based arrangement of bacteria into taxonomic groups or taxa . On the basis of similarities or differences in their biochemical, physiological, genetic and morphological properties . Nomenclature: N aming of the taxa according to characters in International rules . Kingdom: Phylum- Proteobacteria Class –Gamma proteobacteria (- ia ) Subclass-( idae ) Order- Enterobacteriales (ales) Suborder-( ineae ) Family- Enterobacteriaceae ( aceae ) Subfamily-( oideae ) Tribe- Escherichieae ( eae ) Genus- Escherichia Species- E. coli

6. Classification : Two Kingdom : Plantae and Animalia . Three Kingdom : Protisa , Plantae and Animalia . Two Empires : Prokaryota , and Eukaryota . Four Kingdom : Monera , Protista , Plantae and Animalia . Five Kingdom : Monera , Protista , Plantae , Animalia and Fungi . 3 domains : Bacteria, Archea & Eucarya 6 kingdom : Bacteria, Protozoa, Chromista , Plantae , Fungi & Animalia BACTERIA A RCHAE PROKARYOTES Eukaryotes. Eg . Higher plants and animals.

7. Difference between Prokaryotes and Eukaryotes Prokaryotes Do not have membrane bound nucleus. Pro- Primitive nucleus. Ex: Bacteria, Blue green algae. Eukaryotes Membrane bound organelles. Eu - True nucleus. Ex: Plant and Animal Cell, Protozoa, Fungi, Other Algae.

8. ARCHEA EUBACTERIA Live in Extreme conditions . Pseudomurein No muramic acid Seen in enivironments . True bacteria Human pathogens Muramic acid Human pathogens

9. 9 Eukaryotic cell Prokaryotic cell Gram + Gram - Cell wall Rough endoplasmic reticulum Mitochondria (e.g . animal) Nucleoid Nucleus Cell membrane Cytoplasm Flagellum Cell (inner) membrane Outer membrane Ribosomes Granule Cell wall Capsule Pili

10. Bacterial Cell

11. MORPHOLOGY Bacteria usually measured in Microns(µ) or micrometer(µm). 1µm = 1000mm. Shape : cocci – oval or spherical in shape, ex. Staphylococcus Bacilli or Rod – Rod shape , ex. E.coli , Pseudomonas Spiral – thin spirally coiled, ex. Treponema , Leptospira Comma- comma shape , ex. Vibrio

12. Cell Wall Cell wall Gram Positive Gram Negative

13. Peptidoglycan Layer Lipid Content Teichoic acid Lipopolysaccharide Penta glycine Bridge Example Composition Gram Positive Gram Negative Thicker -15-80nm Nil or Scanty(2-5%) Present Absent Present Staphylococcus, Bacillus Thinner( 2nm) Present (15-20%) Absent Present ( Endotoxin ) Absent Klebsiella , Pseudomonas, E.coli

14. Peptidoglycan Peptidoglycan

15. Functions- Cell Wall Protection to the cell- Osmotic Lysis Gives rigidity and shape of the cell Cell division Protect from toxin, Heavy metals, Antibiotics, etc. Contain Virulence factors – Pathogenicity

16. Cell Membrane Also called as Plasma membrane Essential for survival of bacteria. Composed of Bilayered Phospholipids and several proteins ( Integeral and peripheral proteins). Functions: Semipermeable membrane Transport systems- Proteins and enzymes involved in uptake of nutrients and waste excretion. Oxidative phosphorylation occurs at cell membrane (since there are no mitochondria).

17. Cell Wall Appendages Capsule and slime layer : Present outside of the cell wall Well organised - Capsule Un organised - Slime Layer Mostly Polysaccharide. Function : Protects from phagocytosis Prevent from cell drying out Protects from Lysozyme Biofilm formation and adhesion

18. 2. Flagella It is thread like appendages, protruding from the cell wall, Helps in the Motility of bacteria Measure – 5-20µm in length and 0.01-0.02µm in thickness. It contain, Basal part – 4 rings in gram negative ( L,P,S,M). Gram Positive – 2 basal ring. Hook – Short, curved flexible segment. Filament - contain Flagellin

19. Filament Filament Hook Hook Basal body Basal body

20. Types of Flagella Monotrichous - the flagellum is located at the end of the cell. Lopotrichous - flagella appear to have a tuft (" lopho ") of hair (" trichous ") at one or both ends. Ex. Bartonella bacilliformis Peritrichous - Flagella are distributed uniformly over the surface of each bacterial cell. Ex Proteus vulgaris Amphitrichous - Bacteria have a single flagellum at each pole. Ex. Spirillum serpens

21. TYPES OF FLAGELLA .

22. Pilli Short, fine, hair-like appendages Thinner than flagella not involved in motility Pilli – made up of protein – Pillin Acts as anttigenic , Sex pilli helps in gene transfer Fimbriae Fimbriae - small, measuring o.5 µm long and 10 nm thickness Bacteria – more than 1,000 fimbriae Helps in Adhesion ,

23. Axial filaments spirochetes similar function to flagella run lengthwise along cell snake-like movement 25

24. Bacterial Spore Dormant cell , formed within the parent cell – Endospores . Produced when starved (Unfavorable condition) Resistant to adverse conditions - high temperatures - organic solvents contain calcium dipicolinate Example : Bacillus and Clostridium

25. These are characteristically seen with some of the rods. Mostly gram positive rods. S een in some of the rods. Mostly gram positive rods. Central, Ex : Cl.bifermentans Subterminal , Ex : Cl. Perfringens Terminal Oval, Ex : Cl.tertium Terminal Round, Ex : Cl.tetani Ex; Bacillus anthracis Protude outside the body Inside the bacillary body Central Swollen sporangium Terminal Sub terminal

26. Mesosomes Conuoluated or multilaminated membraneous bodies Formed- invaginations of plasma membrane into cytoplasm Shape- vesicle, tubules or lamellae. Site of the respiratory enzymes, responsible of compartmenting of DNA at cell division and spourlation . Types: 1. Septal mesosomes , 2. Lateral mesosomes Intracytoplasmic Inclusion bodies Storeage site of nutrients Formed under nutrient deficiency and disappear when the deficient nutrients are supplied. Types : 1. Organic inclusion bodies 2. Inorganic inclusion bodies EX: Glycogen granules and polyhydroxy butyrate granules. EX: sulfur granules, metachromatic granules

27. Protoplast : Gram positive cell wall is almost completely destroyed by lysozyme Cellular contents surrounded by plasma membrane if lysis does not occur. Wall less cell – protoplast. Cell wall lacking but still metabolism is carrying out. Shape : Spherical Spheroplast : Gram negative cell wall is not destroyed to some extent when lysozyme applied. Cellular contents, plasma membrane and remaining outer wall layer – Spheroplast . Shape : Spherical. Capable of reverting into parent bacterial form when cell wall inhibitor is removed frrom culture medium.

28. Branching Bacteria These are considered to be the higher bacteria,existing in a branching pattern. Ex. Actinomycetes Actinomycetes are a specific group as bacteria. Morphologically they resemble fungi because of their elongated cells that branch into filaments or hyphae