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  • 1. Morphology of bacteria Deepa Babin Travancore Medical college
  • 2. Size of BacteriaAverage bacteria 0.2 – 1.5 micrometre (µm)in diam.Resolution of unaided eye-200 microns RBC is 7.5 µm in diam.
  • 3. Cell• The cell is the basic unit of life• Based on the organization of the cellular structures, cells can be divided into 2 groups:• Eukaryotes-Fungi,Some algae,slime moulds,Protozoa• Prokaryotes-Bacteria,blue green algae
  • 4. Morphology
  • 5. Differences Prokaryote EukaryotesNucleus Absent (one circular) Present(linear more than one chromosome)• Cytoplasm Absent Present• Sterols Absent Present• Muramic acid Present Absent
  • 6. Shapes of Bacteria• Coccus –Spherical or oval – Chain =- Streptoccus – Cluster - Staphylococcus – -Diplo-neisseria• Bacillus – Chain - Streptobacillus – Chinese letter pattern-Corynebacterium• Coccobacillus -Acinetobacter• Vibrio – curved or comma• Spirillum –rigid spiral forms• Spirochetes-flexible spiral forms• Actinomycetes-branching spiral forms• Mycoplasma-cell wall deficient
  • 7. Coccus
  • 8. Bacillus
  • 9. Vibrio leptospira
  • 10. Spirillum&Mycoplasma
  • 11. Actinomycetes
  • 12. Bacterial Cell
  • 13. Bacterial Structures• Cell Wall• Plasma Membrane• Cytoplasm• Ribosomes• Mesosomes• Nucleus,plasmids• Intracytoplasmic Inclusions• Pili or Fimbriae• Flagella• Capsule/Slime layer• L forms or Involution forms• Spores
  • 14. Cell Wall• Determine shape of bacteria• Strength prevents osmotic rupture• 20-40% of dry weight of bacterial cell• Does not stain with ordinary stains• Some antibiotics effect directly – Penicillin• Cell wall consists of Peptido-glycan Polymer (amino acids + sugars)• Sugars-NAG (N acetyl glucosamine) & NAM-(N acetyl muramic acid)• Arranged in alternating chains crosslinked by peptide chain
  • 15. CELL WALL• Gram positive cell wall contains thick layers of teichoic acid as surface Ag• Gram negative thinner cell wall-contains• 1. Lipopolysaccharide-lipid responsible for endotoxic activity,Polysaccharide for antigen specificity• 2.Outer membrane –proteins known as porins-which permit the passage of small molecules
  • 16. Cytoplasmic membrane(cell memb)• Thin layer between cell wall enclosing cytoplasm Bilayer Phospholipid• Acts as a permeability barrier to & from cytoplasm• Respiratory enzymes are present• Damage cause cell death
  • 17. Cytoplasm• 80% Water {20% Salts-Proteins) – Osmotic Shock important• Nucleus-devoid of nuclear memb so called nucleoid• DNA is circular, Haploid• Attached to plasma membrane and replicates by binary fission
  • 18. • Ribosomes-protein synthesis-(Antibiotics like T,Streptomycin acts on Ribosomes)• Mesosomes-Invagination of plasma memb in to cytoplasm- More Respiratory enzymes are present• Plasmids- extra circular DNA – Mutation -Antibiotic Resistance
  • 19. Intracytoplasmic Inclusions• -They are reserve of energy mainly seen in nutrient deficient condition• -Mainly-Volutin,Lipids – (Bacillus,TB),Polysaccharides- (protozoa,fungus),crystals• -Volutin - Babes-Ernst granules or Metachromatic granules(reddish purple- Albert’s or Neisser’s stain)
  • 21. Flagella• Motility – movement• Long hollow tubular structures attached to cell membrane(0.2µm)• Viewed by Electron microscope• Antigenic• It consists of a Filament,Hook,Basal body• Protein subunits called-“flagellin”• Flagellum is attached to hook made up of different protein• Basal body consists of outer and inner rings inserted in to small rod like structure,outer ring is attached to cell wall and inner ring attached to cell membrane.• Basal body rotates flagellum either clockwise and anticlockwise to move bacteria
  • 22. • Swarming occurs with some bacteria – Spread across Petri Dish – Proteus species most evident• Arrangement basis for classification – Monotrichous -Single flagella Eg:Vibrio cholerae – Lophotrichous - Tuft at one end-Spirilla – Amphitrichous - Single or tuft both ends- Pseudomonas - Peritrichous- All around bacteria-Salmonella typhi - Atrichous-No flagella
  • 23. Arrangement Lophotrichous -
  • 24. Fimbriae
  • 25. Fimbriae and Pili• Short,thin hair like protein appendages made of protein subunits-Pillin – smaller than flagella – orginate from cell memb- Electron microscope – organ of adhesion – Fimbriae are antigenic – E. coli has numerous types • K88, K99, F41, etc.• F1-Sex pili ; used in conjugation – Exchange of genetic information
  • 26. Capsule or Slime Layer• Sticky,viscid bacterial secretion around cell surface• Glycocalyx - Polysaccharide on external surface• Adhere bacteria to surface – S. mutans and enamel of teeth• Virulence factor• -Prevents Phagocytosis• Capsule can be demonstrated by negative staining with India ink preparation• -Clear halo around bacteria against dark background• Quellung reaction or Capsule swelling-( Neufeld)-Capsulated bacteria is mixed with its specific anticapsular serum and examined under microscope capsule becomes very prominent and appears swollen due to increase its refractivity
  • 27. Capsule-negative staining
  • 28. Endospores-• Resistant structure-RESTING STAGE – Heat, irradiation, cold – Boiling >1 hr still viable• Bacillus stearothermophilus -spores – Used for quality control of heat sterilization equipment• Bacillus anthracis - spores – Used in biological warfare
  • 29. Endospore
  • 30. Spore• 1.Germinal groove• 2. Outer cortical layer 3 . Cortex• 4 .Internal spore coat• 5 .Sub coat material• 6. Outer spore coat• 7 .Cytoplasmic membrane• 8.Cell wall primordium• Spores are destroyed by AUTOCLAVING AT 121º C FOR 15 MINUTES
  • 31. 1. Central bulging-2.Central not bulging3.Subterminal bulging4. Subterminal not bulging5.Terminal spherical6. Terminal oval
  • 32. Pleomorphism and Involution forms-Due to defective cell wall synthesis -varies size and shape• L forms-Kleineberger-Nobel –Streptobacillus moniliformis-swollen cells• Due to Penicillin or other interference
  • 33. Thank you