ABXR 2

Question 1

Does multiple resistance occur independently?

Answer 1

No already exists together
-bacterial cells can acquire genes for resistance or for virulence by obtaining large pieces of DNA from other bacteria or bacteriophage

Question 2

What is transformation?

Answer 2

1. naked DNA released by donor cell (lysis)

2. uptake of DNA by recipient cell (competence)

Question 3

How does transformation work?

Answer 3

• when cell senses pheromones it becomes competent
• expresses machinery for getting in DNA
  1. DNA binding proteins
  2. nucleases-single stranded
  3. pore to bring in the single stranded DNA
  4. DNA binding to proteins until it can reach the homologous portion in the chromosome where it can bind and homologously recombine

Question 4

What are the three fates of the exogenote?

Answer 4

1. degraded(lost to nucleases)
2. circularized (lost to dilution)
3. recombined (stably retained)

Question 5

What is conjugation

Answer 5

cell-cell mating

• r plasmid in donor
• sex pillus
• r plasmid in recipient

Question 6

What is the clinical relevance of conjugation?

Answer 6

1. rapid dissemination of drug resistance via conjugal R plasmid or conjugal transposons
2. mediates inter-species transfer transfer from non-pathogenic bacteroides to pathogenic shigella or e coli

Question 7

What is transduction?

Answer 7

mediated by bacteriophage
composed of
1) protein capsid
2) DNA or RNA

• phage can carry virulence factors
  ex. beta toxin by diphtheria or cholera toxin by vibrio cholerae CTX phage

Question 8

What is the host chromosome cell that carries the prophage called?

Answer 8

lysogen

Question 9

What does antibiotic preparations that are contaminated by DNA increase the chance of?

Answer 9

genetic exchange

via transformation between antibiotic-producers and pathogens