Bacteria

Question 1

What are the components of a bacteria?

Answer 1

Cytoplasm which contains free ribosomes and a single chromosome (ds DNA) in the nucleoid

Cell envelope:

• Gram positive peptidoglycan wall
• Gram negative lipid bilayer

External structure:

• pili
• capsule
• flagella

Question 2

What are the various features that can be used to identify bacteria?

Answer 2

1. Cell wall structure (gram negative or gram positive)
2. Shape and arrangement of cells (morphology)
3. Atmospheric requirements
4. Temperatures suitable for growth
5. Speed of growth
6. Metabolic products
7. Carbohydrate utilisation
8. Tolerance of adverse conditions
9. DNA

Question 3

What are the different types of structural virulence factors?

Answer 3

Biofilm forming compounds (mix of carbohydrates, proteins and DNA)

• sticky, glue like substance
• Attached bacteria to surfaces
• Gives protection against disinfectants, antibiotics, immune system and physical force
• Loves catheters and artificial heart valves

Endotoxins or lipopolysaccharide (LPS)

• Found in the outer membrane or gram negative bacteria
• Secreted as extracellular LPL blebs as a defense mechanism (antibodies are directed to the blebs)
• Highly immunogenic: inflammation

Exotoxins are secretes as proteinaceous toxins

• active on a specific pathway in the host
• Fomaldehyde inactivated exotoxins ‘toxoids’ make good vaccines