Studies on the promoter specificity determinants and modulators of the prokaryotic transcription machinery

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PhD; 2021; Molecular biophysics

Bacteria adapt to a wide range of environmental conditions by synchronizing transcription with changes in the extracellular environment. This is achieved by the synchronized action of two-component systems, Extra Cytoplasmic Function (ECF) σ factors and myriad one-component systems that combine the roles of both sensors as well as transcription factors. While two-component systems correlate histidine kinase activity with changes in the transcription of target genes, in the case of ECF σ factors, this signal transduction is brought about by the release of free σ factors in the bacterial cell upon specific extracellular triggers. This, in turn, rapidly re-engineers the expression profile. One-component systems are simpler sensor/transcription modulators that operate on specific target proteins. Amongst these three mechanisms, the ECF σ factors, in particular, achieve both-specific expression of genes in a regulon as well as the magnitude of change in expression. This feature, alongside the finding that bacteria often have multiple ECF σ factors, suggests that the activity of ECF σ factors play a dominant role in governing the expression profile of a bacterial cell.