2008, pp 313-337

The Role of RpoS in Bacterial Adaptation

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Bacterial adaptation to changing conditions and to the host environment requires coordinated changes in gene expression that permit more efficient use of metabolites and increased survival. An important form of gene control is through the use of alternative sigma factors that direct RNA polymerase to recognize a distinct group of genes. One such sigma factor is RpoS, which is widely present in many Gram-negative bacteria. RpoS is important for adaptation under nutrient-limited conditions, but, interestingly, rpoS mutants may have a selective growth advantage under such conditions. In this chapter, we review the factors that control RpoS induction, activation, and attenuation, including hns, dsrA, and other regulators. The nature of the RpoS regulon, including the factors it controls and their potential metabolic roles in adaptation, is discussed in terms of the physiological challenges faced by the cells during stress. We review the recent contribution of global gene expression studies performed with microarrays and genetic screening protocols to exhaustively characterize this important regulon. Finally, we consider the specific roles of RpoS in pathogenicity in the mammalian host and in natural bacterial isolates.