1. Morphology of bacteria
Deepa Babin
Travancore Medical college

2. Size of Bacteria
Average 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 Eukaryotes
Nucleus 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

8. Coccus

9. Bacillus

10. Vibrio leptospira

11. Spirillum&Mycoplasma

12. Actinomycetes

13. Bacterial Cell

14. 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

15. 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

17. 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

18. 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

19. 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

20. • 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

21. 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)

22. STRUCTURE OF FLAGELLA

23. 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

24. • 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

25. Arrangement
Lophotrichous -

26. Fimbriae

27. 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

28. 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

29. Capsule-negative staining

30. 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

31. Endospore

32. 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

33. 1. Central bulging-
2.Central not bulging
3.Subterminal bulging
4. Subterminal not bulging
5.Terminal spherical
6. Terminal oval

34. 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

35. Thank you