Abstract
For many bacteria, successful growth and survival depends on efficient adaptation to rapidly changing conditions. In Escherichia coli, the RpoS alternative sigma factor plays a central role in the adaptation to many suboptimal growth conditions by controlling the expression of many genes that protect the cell from stress and help the cell scavenge nutrients. Neither RpoS or the genes it controls are essential for growth and, as a result, the composition of the regulon and the nature of RpoS control in E. coli strains can be variable. RpoS controls many genetic systems, including those affecting pathogenesis, phenotypic traits including metabolic pathways and biofilm formation, and the expression of genes needed to survive nutrient deprivation. In this review, I review the origin of RpoS and assess recent transcriptomic and proteomic studies to identify features of the RpoS regulon in specific clades of E. coli to identify core functions of the regulon and to identify more specialized potential roles for the regulon in E. coli subgroups.
Highlights
Escherichia coli, like many free-living bacteria, lives a biphasic lifestyle that consists of alternating periods of rapid growth and nutrient deprivation
Much of our knowledge of bacterial regulation has come from countless studies of a few laboratory E. coli strains grown under laboratory conditions that, while useful, probably imperfectly mimic bacterial growth in the natural environment
This review examines features of the RpoS regulon from a functional and evolutionary perspective and will not include a consideration of the many factors that modulate the regulation of RpoS itself
Summary
Escherichia coli, like many free-living bacteria, lives a biphasic lifestyle that consists of alternating periods of rapid growth and nutrient deprivation These periods may be accompanied by stresses such as desiccation and other adverse chemical/physical conditions including osmotic stress, nutrient deprivation, oxidative stress and acid stress. These diverse environmental challenges require coordinated sensing and response through programmed changes that include efficient physiological adaptation and reprogrammable modulation of gene expression. This can be accomplished, in populations, by evolutionary selection for favorable traits that enhance survival and, in individual cells, through the activation of specific regulatory processes that allow the cell to adapt to new metabolic and physical challenges. Much of our knowledge of bacterial regulation has come from countless studies of a few laboratory E. coli strains grown under laboratory conditions that, while useful, probably imperfectly mimic bacterial growth in the natural environment
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