The sigma(S) (RpoS) subunit of RNA polymerase is the master regulator of the general stress response in Escherichia coli and related bacteria. While rapidly growing cells contain very little sigma(S), exposure to many different stress conditions results in rapid and strong sigma(S) induction. Consequently, transcription of numerous sigma(S)-dependent genes is activated, many of which encode gene products with stress-protective functions. Multiple signal integration in the control of the cellular sigma(S) level is achieved by rpoS transcriptional and translational control as well as by regulated sigma(S) proteolysis, with various stress conditions differentially affecting these levels of sigma(S) control. Thus, a reduced growth rate results in increased rpoS transcription whereas high osmolarity, low temperature, acidic pH, and some late-log-phase signals stimulate the translation of already present rpoS mRNA. In addition, carbon starvation, high osmolarity, acidic pH, and high temperature result in stabilization of sigma(S), which, under nonstress conditions, is degraded with a half-life of one to several minutes. Important cis-regulatory determinants as well as trans-acting regulatory factors involved at all levels of sigma(S) regulation have been identified. rpoS translation is controlled by several proteins (Hfq and HU) and small regulatory RNAs that probably affect the secondary structure of rpoS mRNA. For sigma(S) proteolysis, the response regulator RssB is essential. RssB is a specific direct sigma(S) recognition factor, whose affinity for sigma(S) is modulated by phosphorylation of its receiver domain. RssB delivers sigma(S) to the ClpXP protease, where sigma(S) is unfolded and completely degraded. This review summarizes our current knowledge about the molecular functions and interactions of these components and tries to establish a framework for further research on the mode of multiple signal input into this complex regulatory system.

Signal transduction and regulatory mechanisms involved in control of the sigma(S) (RpoS) subunit of RNA polymerase.

https://faculty.washington.edu/korshin/Class-486/JMM(49)31.pdf

Detection and enumeration of coliforms in drinking water: current methods and emerging approaches

In Escherichia coli, the transcription factor sigmaS, encoded by rpoS, controls the expression of a large number of genes involved in cellular responses to a diverse number of stresses, including s...

http://www.loewenlabs.com/peter/wp-content/themes/atahualpa/Manuscripts/CJM_44_707.pdf

Regulation in the rpoS regulon of Escherichia coli

Aging, or senescence, is the progressive deterioration of every bodily function over time. A fundamental question that applies to all life forms, including growth-arrested bacteria, is why growing older by necessity causes organisms to grow more fragile. In this work, we demonstrate that the levels of oxidized proteins is correlated to the age of a stationary-phase Escherichia coli culture; both disulfide bridge formation of a cytoplasmic leader-less alkaline phosphatase and protein carbonyl levels increase during stasis. The stasis-induced increase in protein oxidation is enhanced in cells lacking the global regulators OxyR and ςs. Some proteins were found to be specifically susceptible to stasis-induced oxidation; notably several TCA cycle enzymes, glutamine synthetase, glutamate synthase, pyruvate kinase, DnaK, and H-NS. Evidence that oxidation of target proteins during stasis serves as the signal for stationary-phase, developmental, induction of the heat shock regulon is presented by demonstrating that this induction is mitigated by overproducing the superoxide dismutase SodA. In addition, cells lacking cytoplasmic superoxide dismutase activity exhibit superinduction of heat shock proteins. The possibility that oxidative sensitivity of TCA cycle enzymes serves as a feedback mechanism down-regulating toxic respiration is discussed.

/pdf/bacterial-senescence-stasis-results-in-increased-and-3psj7avj8i.pdf

Bacterial senescence: stasis results in increased and differential oxidation of cytoplasmic proteins leading to developmental induction of the heat shock regulon

This map is an update of the edition 9 map by Berlyn et al. (M. K. B. Berlyn, K. B. Low, and K. E. Rudd, p. 1715–1902, in F. C. Neidhardt et al., ed., Escherichia coli and Salmonella: cellular and molecular biology, 2nd ed., vol. 2, 1996). It uses coordinates established by the completed sequence, expressed as 100 minutes for the entire circular map, and adds new genes discovered and established since 1996 and eliminates those shown to correspond to other known genes. The latter are included as synonyms. An alphabetical list of genes showing map location, synonyms, the protein or RNA product of the gene, phenotypes of mutants, and reference citations is provided. In addition to genes known to correspond to gene sequences, other genes, often older, that are described by phenotype and older mapping techniques and that have not been correlated with sequences are included.

/pdf/linkage-map-of-escherichia-coli-k-12-edition-10-the-4xep962ryl.pdf

Linkage Map of Escherichia coli K-12, Edition 10: The Traditional Map

DnaK is essential for starvation-induced resistance to heat, oxidation, and reductive division in Escherichia coli . Studies reported here indicate that DnaK is also required for starvation-induced osmotolerance, catalase activity, and the production of the RpoS-controlled Dps (PexB) protein. Because these dnaK mutant phenotypes closely resemble those of rpoS (ς 38 ) mutants, the relationship between DnaK and RpoS was evaluated directly during growth and starvation at 30°C in strains with genetically altered DnaK content. A starvation-specific effect of DnaK on RpoS abundance was observed. During carbon starvation, DnaK deficiency reduced RpoS levels threefold, while DnaK excess increased RpoS levels nearly twofold. Complementation of the dnaK mutation restored starvation-induced RpoS levels to normal. RpoS deficiency had no effect on the cellular concentration of DnaK, revealing an epistatic relationship between DnaK and RpoS. Protein half-life studies conducted at the onset of starvation indicate that DnaK deficiency significantly destabilized RpoS. RpoH (ς 32 ) suppressors of the dnaK mutant with restored levels of RpoS and dnaK rpoS double mutants were used to show that DnaK plays both an independent and an RpoS-dependent role in starvation-induced thermotolerance. The results suggest that DnaK coordinates sigma factor levels in glucose-starved E. coli.

/pdf/roles-of-dnak-and-rpos-in-starvation-induced-thermotolerance-3porwduc8i.pdf

Roles of DnaK and RpoS in starvation-induced thermotolerance of Escherichia coli

Municipal effluent is the largest reservoir of human enteric bacteria. Its public health significance, however, depends upon the physiological status of the wastewater bacterial community. A novel immunofluorescence assay was developed and used to examine the bacterial growth state during wastewater disinfection. Quantitative levels of three highly conserved cytosolic proteins (DnaK, Dps, and Fis) were determined by using enterobacterium-specific antibody fluorochrome-coupled probes. Enterobacterial Fis homologs were abundant in growing cells and nearly undetectable in stationary-phase cells. In contrast, enterobacterial Dps homologs were abundant in stationary-phase cells but virtually undetectable in growing cells. The range of variation in the abundance of both proteins was at least 100-fold as determined by Western blotting and immunofluorescence analysis. Enterobacterial DnaK homologs were nearly invariant with growth state, enabling their use as permeabilization controls. The cellular growth states of individual enterobacteria in wastewater samples were determined by measurement of Fis, Dps, and DnaK abundance (protein profiling). Intermediate levels of Fis and Dps were evident and occurred in response to physiological transitions. The results indicate that chlorination failed to kill coliforms but rather elicited nutrient starvation and a reversible nonculturable state. These studies suggest that the current standard procedures for wastewater analysis which rely on detection of culturable cells likely underestimate fecal coliform content.

/pdf/bacterial-growth-state-distinguished-by-single-cell-protein-zovsktim97.pdf

Bacterial Growth State Distinguished by Single-Cell Protein Profiling: Does Chlorination Kill Coliforms in Municipal Effluent?

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Roles of DnaK and RpoS in starvation-induced thermotolerance of Escherichia coli

Bacterial Growth State Distinguished by Single-Cell Protein Profiling: Does Chlorination Kill Coliforms in Municipal Effluent?