Bacteria

Question 1

Name the two Domains of Bacteria

Answer 1

Eubacteria and Achaebacteria

Question 2

What is the principal difference between prokaryotes and eukaryotes?

Answer 2

Prokaryotes do not have a nucleus and their DNA is not organised into chromosomal structures like humans.

Question 3

What is the name for Bacteria that just colonise us without causing harm

Answer 3

Commensal Organisms

Question 4

What is the name for harmful bacteria

Answer 4

Pathogens

Question 5

What is the name for pathogens which can cause disease irrespective of our biological defences

Answer 5

Full Pathogens

Question 6

Define the two types of opportunistic pathogens

Answer 6

Those facilitated by gaps in our PHYSICAL defenses (e.g. cuts in the skin) and those facilitated by gaps in our IMMUNOLOGICAL defenses (e.g. due to neutropenia, immunosuppression, HIV infection etc)

Question 7

What are virulence factors? And name three examples

Answer 7

Virulence Factors: Bacteria-associated molecules that are required for a bacterium to cause disease
Tissue destroying enzymes
Toxins that inhibit cellular pathways in the host making it easier for the bacteria to grow
Toxins that destroy our immune defences.

Question 8

What is the average size of bacteria?

Answer 8

Size: about 0.1 - 3 microns (3 x 10-6 m)

Question 9

Name thee mesh of polymers of polysaccharides and peptides that constitutes a bacterial cell wall.

Answer 9

Peptidoglycan

Question 10

How does penicillin affect bacteria?

Answer 10

The enzymes which make peptidoglycan are the target for inhibition by antibiotics such a penicillin.

Question 11

Name the three routes in which bacteria can rapidly transfer genes between each other

Answer 11

Bacteria can rapidly transfer genes between themselves via several routes:

Conjugation (direct exchange of DNA through bacterial contact – like mating);
Transformation ( uptake of free DNA);
Transduction (transfer of DNA by bacterial viruses called bacteriophages).

Question 12

Name the 5 phenotypic features that can help us to identify bacteria

Answer 12

1. Shape – cocci, rod (bacillus) , curved, spiral; whether they grow in single cells, in clusters or in chains
2. Gram staining – Gram positive (Gram +ve) or Gram negative (Gram -ve)
3. Type of respiration – anaerobic, microaerophilic or aerobic
4. Ability to produce spores or show special structures such a granules, flagella (for motility)
5. Enzyme profiles

Question 13

What differences does gram staining show?

Answer 13

Gram Staining
Gram +ve bacteria have a large peptidoglycan layer on the outside of a cell membrane.
Gram -ve bacteria have 2 membranes, with a small layer of peptidoglycan between an outer and inner membrane.

Question 14

What are the three factors that we use to microscopically differentiate bacteria?

Answer 14

Morphology, growth and biochemical profiling

Question 15

What are API Strips?:

Answer 15

Strips that can test for particular enzymes or fermentation capacity (coloured biochemical indicators) when bacteria are introduced.