This document discusses various cell wall appendages of bacteria, including capsules, fimbriae/pili, and flagella. It describes their composition, structure, function, and methods of detection. Capsules and slime layers are made of polysaccharides or polypeptides and help bacteria evade the immune system. Flagella are protein structures that aid in motility. Fimbriae are thinner than flagella and assist in adhesion. The document also briefly covers bacterial spores, cell division, growth curves, and factors that influence bacterial growth such as oxygen, temperature, and nutrition.

1. CELL WALLAPPENDAGES
Dr. Sumesh Kumar Dash
Department of Microbiology,
IMS & SUM Hospital

2. • Capsule
• Fimbria/pili
• Flagella

3. CAPSULE & SLIME LAYER
Bacteria possessing amorphous sticky material outside cell wall -
glycocalyx
• Capsule- glycocalyx layer well organized & not easily washed off.
• Slime layer- glycocalyx layer in the form of diffuse, unorganized loose
material that can be easily washed off.
• Capsules are polysaccharide in nature, except Bacillus anthracis
(polypeptide).
• Also seen in fungi. Eg: Cryptococcus neoformans

4. Functions/uses
• Contribute to bacterial virulence
• Protects from phagocytosis
• Prevent complement mediated cell lysis
• Protects from action of lysozyme & bacteriophages
• Source of nutrients & energy
• Capsules as vaccines- pneumococcus, meningococcus & Hib

5. Demonstration
Negative staining
• india ink & nigrosine
• clear refractile halo bacteria in background black.
Electron microscopy

6. FLAGELLA
• Thread like appendages protruding from the cell wall
• Organ of locomotion.
• Measures: 5-20 µm in length & 0.02 µm in thickness
• Made up of a protein (flagellin)
• Flagellar antigens induce specific antibodies- not protective
but are useful in serodiagnosis.

8. Detection
1. Direct detection:
• Tannic acid staining
• Dark ground, phase contrast or electron microscope
2. Indirect detection:
• Semisolid medium
• Hanging drop/wet mount method

9. FIMBRIAE/PILI
• Short, fine, hair like appendages arise from cell membrane,
thinner than flagella.
• Measure: 0.5 µm long & 10 nm thick.
• Made up of protein called pilin.
• Not related to motility- found in both motile & non motile
organisms
• Organs of adhesion
• Bacterial gene transfer

10. BACTERIAL SPORES
• Highly resistant dormant stage of bacteria formed in
unfavorable conditions as a result of depletion of nutrients.
STRUCTURE:
Inner to outer- core cortex coat exosporium

11. Shape & position of spores
• Position- central/subterminal/terminal
• Shape- oval/spherical
• Width- non bulging (Bacillus) & bulging (Clostridium)

12. GERMINATION
Transformation of dormant spores into active
vegetative cells when grown in nutrient rich
medium.

13. CELL DIVISION
• Bacteria divided in binary fission.
• GENERATION TIME: time required for a
bacteria to give rise to two daughter cell
under optimum condition.
e.coli – 20min
m.tuberculosis – 20h
m.leprae – 20days

14. BACTERIAL COUNTS
TOTAL COUNT
Total number of bacteria cell present in a sample
regardless living or dead.
VIABLE COUNT
Measure the number of living cell i:e the cell
capable of multiplication.

15. BACTERIAL GROWTH CURVE
• When bacteria is inoculated in a suitable medium
and incubated, their growth follow a definite
course & is k/a Bacterial Growth Curve.
• In this graph bacterial count is determined at
different interval & plotted in relation to time.
• 4 Phase
Lag phase
Log phase
Stationary phase
Phase of decline

16. LOG LAG STATIONARY DECLINE
DIVISION No Yes Yes No
DEATH No No Yes Yes
TOTAL COUNT Flat Raises Raise Flat
VIABLE COUNT Flat Raises Flat Falls
SPECIAL
FEATURE
Accumulation
of enzyme and
metabolites.
Attend
maximum size.
Uniformly
stain.
Biochemically
active
Growth almost
complete.
Sporulation,
Bacteriocins
Exhaustion of
nutrients.

17. FACTOR AFFECTING GROWTH
OXYGEN
1. Obligate aerobe: Required oxygen for growth
(Pseudomonas, M.tuberculosis etc.)
2. Facultative anaerobes: aerobe but can grow
anaerobically. (E.coli, S.aureus etc.)
3. Obligate anaerobes: Grow absences of oxygen
(Clostridium)
4. Facultative aerobe: anaerobe but can grow aerobically
(Lactobacillus)
5. Microaerophilic bacteria: Grow in presences of low
oxygen (Campylobacter & Helicobacter)

18. CARBONE DIOXIDE
Capnophilic bacteria required high amount of CO2 for
growth. (Streptococcus pneumoniae)
TEMPERATURE
Psychrophiles: Below 20 c (Pseudomonas)
Mesophiles: 25-40 c
Thermophiles: 55-80 c (Geobacillus stearothermophilus)

19. pH
• Most of bacteria grow in pH 7.2 – 7.6
LIGHT
• Most of bacteria grow well in darkness.
• They are sensitive to UV and radiation.
MOISTURE & DESICCATION
• Water is essential ingredient of bacteria, so drying is
lethal to them.
• Spores can survive desiccation

20. BACTERIAL NUTRITION
For growth and multiplication the nutrition
requirement are Water, Source of Carbon,
Source of Nitrogen and some inorganic salts.
• Phototrophs: Derive energy source from
sunlight.
• Chemotrophs: Obtain energy from chemical
reaction.
• Autotrophs: Synthesis all their organic
product.
• Heterotrophs: Depend on others for their
nutrition.

21. THANK YOU