Regulation of genes coding for bacterial virulance factors

Question 1

When are virulence factors produced?

Answer 1

Virulence factors are generally not produced all of the time, but only when they are needed.

Question 2

What are adaptive challenges faced by pathogenic Bacteria in water ?

Answer 2

low temperature
low nutrient and osmotic strength
pH near neutral
O2 available
respiratory metabolism
free iron available
adhesins to stick to rocks

Question 3

What are adaptive challenges faced by pathogenic Bacteria in Humans ?

Answer 3

higher temperature (37oC)
higher osmotic strength, C and energy sources abundant
low pH then higher pH
low or no O2
fermentative metabolism
iron bound to haem
adhesins to stick to cells
exposure to bile salts

Question 4

Why is it important that bacteria adapt?

Answer 4

They need to adapt to survive and colonise these differing environments, and proteins that are useful in one environment (for example the type III secretion system) may be completely dispensable for survival in another.

Question 5

What are some ways that virulence genes can be regulated ?

Answer 5

—Change in number of transcripts (transcriptional regulation)

–DNA rearrangements

–Change in the number of proteins (translational regulation)

Question 6

What are examples of change in the number of transcripts ( transcriptional regulation) ( as a type of regulation) ?

Answer 6

• activators
• repressors

Regulating the promoter of a gene, switching the gene on (activation) or switching it off (repression). Relatively straight-forward.

Question 7

What are examples of change in the DNA rearrangements ( as a type of regulation) ?

Answer 7

• Slipped-strand mispairing
• Gene conversions
• Gene inversions
• Insertions and excisions
• Epigenetic changes (cytosine methylation)

tends to be restricted primarily to surface structures that are exposed to the immune system. There are also epigenetic changes that do not alter the sequence of the DNA at all but that change the methylation state of cytosine that can alter the binding of repressors or activators to DNA. Will not have time to go into this in detail but you should be aware that it is also a mechanism for controlling gene expression

Question 8

What are examples of change in the change in the number of proteins ( as a type of regulation) ?

Answer 8

• RNA topology
  This is NOT to regulate at the DNA or transcriptional level but to regulate at the RNA level. So you do not affect the transcription of mRNAs but you affect the rate at which they are translated or degraded.

Question 9

Whats the most commonest virulence factor regulation system?

Answer 9

• transcriptional regulation of bacterial virulence factors