Bacterial Genetic Variation, Gene Transfer, and Evolution of Virulence

Question 1

List the three ways by which bacteria can develop genetic variation.

Answer 1

Spontaneous mutation, recombination, and acquisition of new DNA fragments

Question 2

Describe phase variation.

Answer 2

Bacteria can have mutations in which promoters invert in the DNA sequence, thus switching to a new gene expression; this helps bacteria express new antigens.

Question 3

Define transposon.

Answer 3

(n.) a segment of DNA contained within a bacterial chromosome, phage chromosome, or plasmid that has the property of being enzymatically moved from one DNA location to another (WITHIN the same bacterium)

Question 4

What are some typical features of bacterial plasmids?

Answer 4

They are self-replicating and circular; they range in size; they are usually not necessary for viability.

Question 5

Many changes in bacterial transcription occur in response to changes in ____________.

Answer 5

extra-cellular iron concentration; for example, diptheria toxin is only expressed in low-iron environments (iron is typically lower in organisms than in the environment)

Question 6

In salmonella typhimurium, the bacterial can vary between _________ types, while in neisseria gonorrhea the change occurs in ________.

Answer 6

flagellar antigenic; pili types

Question 7

Bacterial transduction can occur by ___________.

Answer 7

viral-mediated sampling of bacterial DNA or plasmids

Question 8

What are lysogens?

Answer 8

Lysogens are viruses that enter a cell’s genome but do not divide to create new virions at an appreciable rate.

Question 9

F+ bacteria are those that _________.

Answer 9

donate plasmids to other bacteria