THE ROLE OF THE SIGMA-FACTOR SIGMA(S) (KATF) IN BACTERIAL GLOBAL REGULATION

The protein encoded by katF (also known as nur, appR, csi-2, abrD, and rpoS in various alleles) has been biochemically confirmed to be an al ternate sigma transcription factor and renamed sigma(S). Its synthesis is controlled transcriptionally and posttranscriptionally by as yet u ndefined mechanisms that are active well into stationary phase, sigma( S) controls a regulon of 30 or more genes expressed in response to sta rvation and during the transition to stationary phase. Proteins in the regulon, many of which have not been characterized, enhance long-term survival in nutrient-deficient medium and have a diverse group of fun ctions including protection against DNA damage, the determination of m orphological changes, the mediation of virulence, osmoprotection, and thermotolerance. Differential expression of subfamilies of genes withi n the regulon is effected by supplementary regulatory factors, working both individually and in combination to modulate activity of differen t sigma(S)-dependent promoters.