1. Structure & Physiology of Bacteria
Cell Composition:
@ Flagellum @ Fimbria
@ Pilli @ Capsule
@ Outer membrane @ Cell wall @ Cell membrane @ Mesosome @ Cytoplasm @ Ribosomes @ Nucleoid @ Depot substances
@ Plasmids

3. Flagella
Structure:
@ Composed of : filament, hook, basal body
@ Filament:
# Helical, 10 x cell diameter, 10 µm length
# Diameter 17 nm
# Made up of ovoid protein subunits (flagellin)
# Subunits are 4-11 in a circle
# Subunits form a tube 13.5 nm diameter
# Pitch + wavelength constant for each
bacterial strain.

5. @ Hook:
# Straight & curves at right angle to filament
# Covered by sheath (vibrios, Proteus, Ps.)
# Sheath 56 nm in diameter.
# Arises from cell wall
# Gives flagellum its shape
# Stable to chemicals
# Specific antigenic nature

7. @ Basal body:
# Embedded in cytoplasmic membrane
# Composed of rods and rings (L, P, S, M)
# Gram negative :
@ L & P rings anchored to outer membrane
@ S & M rings anchored to inner membrane
# Gram positive :
@ No outer membrane, so no L & P ring, had
S & M rings.
# Synthesis of filament subunits
# Control movement
# Anchor flagella to cytoplasm.

9. Functions of Flagella
@ Organs of motility to bacteria
@ Spirochaetes locomote without flagella
@ May not be used for movement:
# Bacteria may turn round and move with
flagella pulled behind.
# Protoplasts (no cell wall) have got flagella but
they are non-motile

11. Why Bacteria Move?
@ Motility increases rate of nutrients uptake.
@ Move to areas with best environmental
conditions:
# Higher concentrations of food-stuff
# Away from disinfectants and antibiotics
# Towards high oxygen tension (aerobes)
# Towards low oxygen tension (anaerobes).
@ To pass through mucous secretions and
epithelial barriers.
NOTE: Streptococci non-motile but can pass.

13. Types of Bacterial Movement
@ Brownian movement: oscillation of bacteria in
place due to bombardment of fluid particles.
@ Convection current movement: bacteria move
in same direction due to heat or grease.
@ True movement : bacteria move in different
directions:
# Darting: Pseudomonas
# Wriggling: (التواءات) Spirillum
# Tumbling: (بهلواني) E.coli
# Spiral: Spirochaetes

15. Demonstration of Flagella
@ By light microscope:
* Flagella wound together in a bundle.
* Flagella stains:
* Mordant colloidal solution.
* Suitable dye to stain flagella.
@ By electron microscope in metal preparations
@ By dark-field microscope
@ By motility test.

17. Flagella Arrangements:
A – Monotrichous: Single flagellum extending
from one end of the cell (Vibrio).
B – Lophotrichous: Multiple flagella extending
from one end of bacterial cell
C – Amphitrichous: Single flagellum extending
from the two ends the cell (Spirillum).
D – Peritrichous: Multiple flagella distributed
over the entire bacterial cell (E.coli).

18. Monotrichous
Lophotrichous
Amphitrichous
Peritrichous

19. Bacterial Fimbriae
@ Straight filamentous appendages
@ Extend out from cell surface
@ Present almost only in gram negative bacteria
@ Different from flagella in:
# Present in motile and non-motile bacteria
# More numerous for each cell
# Always borne peritrichously.
# Shorter & half thick than flagella
# Only seen by negative electron microscope

21. @ Culturing bacteria in liquid media stimulates
fimbriae production (fimbriate phase)
@ Culturing on solid media destroys fimbriae
(non-fimbriate phase)
@ In serological typing growth of enterobacteria
on solid agar is done to get rid of fimbriae
and expose somatic antigens.
@ Fimbriae originate from cell membrane
@ Fimbriae are composed of pilin protein

23. Functions of Fimbriae
@ Organs of adhesions & pathogenicity factors
@ Adherence sticks bacteria to areas with
nutrients, oxygen, temperature.
@ Adherence to RBC helps Hemagglutination.
@ Testing for haemagglutination demonstrates
fimbriated bacteria.

25. Types of Fimbriae
Distinguished by their length and width
@ Type 1 : Found in E.coli, Klebsiella, Serratia,
Salmonella, Shigella. Adhesion is inhibited by
adding mannose sugar (Mannose sensitive).
@ Type 2 : Found in Salmonella. No adhesion
or haemagglutination properties.
@ Type 3: Found in Klebsiella & Serratia.
Mannose resistant. Agglutinate only heated RBC
@ Type 4 : Found in Proteus. Mannose resistant

26. Type 1 E. coli
Type 2 Salmonella
Type 3 Klebsiella
Type 4 Proteus

27. Sex Pili
@ Mainly found in enterobacteria.
@ Less than 10 per cell.
@ Longer than 2 µm .
@ Used in conjugation with non-male bacteria.
@ Transfer DNA plasmid fertility factor.
@ Act as receptors for bacteriophages.