\(Escherichia\) \(coli\) responses to acid-stress: signal transduction and gene regulation

Sen, Hrishiraj (2018). \(Escherichia\) \(coli\) responses to acid-stress: signal transduction and gene regulation. University of Birmingham. Ph.D.

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Abstract

Microbial lab-based evolution is a technique to study evolutionary theory. It is a method which can provide insights into the ability of a microbe to adapt to a biological process such as low pH. To investigate pathways that could lead to an acid resistant phenotype in E. coli, we evolved six independent lines or populations of E. coli K-12 MG1655 by iterative growth and dilution experiments for approximately 740 generations at pH 4.5. Clones isolated from evolved populations were significantly fitter than the ancestor at pH 4.5. Five of the six evolved strains had acquired an identical mutation in rpoA, and mutations in cytR in addition to other mutations. PCR analysis of the fossil record of the evolved populations showed that the arcA mutations always arose first followed by the rpoA mutations. Investigating the genetic basis of adaptation showed that the mutations in arcA were loss of function in nature and conferred caused an intermediate increase in fitness. Transcriptional analysis showed a global change in their transcriptional signatures with significant upregulation of the arcA regulon. Our study showed that loss of function of ArcA caused an increase in the RpoS activity of the acid evolved strains leading to a general stress resistant phenotype.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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