antibiotics - lqc 8a

Question 1

Describe what is meant by ‘the evolutionary race’ between bacteria and their hosts

Answer 1

As soon as the host evolves mechanisms to combat the pathogen, i.e. a specific immune response, the pathogen evolves new methods of overcoming the immune system of the host, i.e. by changing the shape of an antigen. The host antibodies and memory cells are now useless

Question 2

why do bacteria evolve so fast- fast reproduction

Answer 2

One E.coli bacterium can divide every 20 minutes producing 2 million new cells in just 7 hours. These cells contain 8000 million genes with about 800 mutations.

Question 3

why do bacteria evolve so fast- very large populations

Answer 3

Usually in the billions, the number of cells containing mutations is vast. Therefore they have a very large gene pool.

Question 4

why do bacteria evolve so quickly- random mutations will be advantageous

Answer 4

These mutations may allow the bacterial cell to use a different food resource, reproduce more quickly, infect other cells more quickly, produce advantageous symptoms in the host for their transmission i.e. coughing or sneezing. Those bacteria with a new advantageous allele are more likely to survive, reproduce and spread from cell to cell and host to host.

Question 5

what is the natural selection pressure acting on bacteria?

Answer 5

the host immune system

Question 6

what is an antibiotic

Answer 6

a chemical substance, produced by microorganisms, which has the capacity to inhibit the multiplication/replication, or even destroy bacteria and other microorganisms.

Question 7

bactericidal antibiotic

Answer 7

Antibiotic that destroys/kills bacteria. Can cause the cell to lyse.

Question 8

bacteriostatic antibiotic

Answer 8

Antibiotic that inhibits the multiplication/replication (NOT growth) of bacteria. The host’s own immune system can then destroy the bacterial population.

Question 9

Outline how antibiotics can disrupt bacterial cell growth and division

Answer 9

1. Inhibition of bacterial cell wall synthesis: If a weak wall forms, this can lead to cell lysis.
2. Disruption of the cell membrane: This can cause changes in permeability that can lead to cell lysis.
3. Inhibition of nucleic acid synthesis, replication and transcription: This can prevent cell division (binary fission) and/or synthesis of enzymes.
4. Inhibition of protein synthesis: Enzymes and other essential proteins are not produced.
5. Inhibition of specific bacterial enzymes: this would inhibit bacterial cell processes but not those of the host.