Use the examples of small RNA regulation in bacteria from slide 22 of the Oct 19

Question

Use the examples of small RNA regulation in bacteria from slide 22 of the Oct 19 lecture for this question. The rpoS gene is expressed at high levels when cells enter stationary phase of growth (when liquid cultures are dense with cells and growth slows) and at low levels during the exponential phase of growth (early rapid growth). An E. coli mutant is isolated that has low levels of rpoS expression at all stages of growth.

A) What is one example of a type of mutation in rpoS or a regulatory gene encoding a small RNA that could account for this phenotype?

B) Explain how your choice from part A would account for the phenotype

Explanation / Answer

A) The gene rpoS encodes sigma factor in E.coli. The sigma factor plays an important role in transcription. It regulates transcription in bacteria. Generally this gene is expressed in late exponential phase.

In E.coli, this gene allows the organism to survive during environmental challenges and also prepares the organism to subsequent stresses.

The RpoS-dependent genes are involved in cell membrane permeability, cell aggregation, and cell morphology. Thus, RpoS gene also controls morphology of in E.coli. The genes that are linked to this gene are osmB, osmY, bola, ftsQAZ.

B) As the gene RpoS is involved in cell permeability, shape, size, and cell aggregation, thus all these are affected due to mutation in RpoS gene. The cells lose their viability because of mutation in RpoS gene and fail to reseal.

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