Microbe Genetic Variability

Describe things that can lead to vertically transferred mutations in bacteria

DNA mutations: spontaneous, replication errors, mutagens

How can DNA be transferred horizontally?

• conjugation

• transduction

• transformation

What is conjugation in bacteria and what does it require?

• horizontal transfer of DNA

• requires cell to cell contact, sex pulus, relaxomosome, T4SS

• plasmid/episome

What is a plasmid?

independently replicating non-chromosomal DNA; contains non-vital DNA; own origin and replicatino

What is an episome

independently replicating plasmids with own origin integrated into chromosome

Describe the steps of conjugation

1. F factors in F+ donor builds sex pilus, makes contact with F- recipient

2. Sex pilus contracts, pulling cells together

3. T4SS constructed in donor, joins cells

4. relaxosome cuts plasmid in donor at OriT, separating one strand via rolling circle replication

5. T4SS puts DNA into recipient cell

6. DNA replicated in recipient, now F+

What is transformation?

• bacterial uptake of DNA lying around

• requires cells with DNA uptake machinery (pilus, nuclease, etc.)

What is transduction and how does it work?

• virus mediated transfer of DNA

• 1. phage infects bacteria

• 2. phage picks up pieces of bacterial chromosome during replication and assembly

• 3. phage can transfer DNA to new recipient after infection

What is a plasmid carrying antibiotic resistance genes called?

R plasmid

what is a transposon?

a segment of DNA that can move from one location in a genome to another

How can R-plasmids move?

• horizontal gene transfer (transduction, transformation, conjugation)

• carried in transposon (moving gene) like ICE and MGI