While the roles of rpoS(Bb) and RpoS-dependent genes have been studied extensively within the mammal, the contribution of the RpoS regulon to the tick-phase of the Borrelia burgdorferi enzootic cycle has not been examined. Herein, we demonstrate that RpoS-dependent gene expression is prerequisite for the transmission of spirochetes by feeding nymphs. RpoS-deficient organisms are confined to the...

Escherichia coli cell viability during starvation is strongly dependent on the expression of the rpoS gene, encoding the RpoS sigma subunit of RNA polymerase. RpoS abundance has been reported to be regulated at many levels, including transcription initiation, translation, and protein stability. The regulatory RNA SsrA (or tmRNA) has both tRNA and mRNA activities, relieving ribosome stalling and...

UNLABELLED Although Escherichia coli is generally considered to be predominantly a commensal of the gastrointestinal tract, a number of recent studies suggest that it is also capable of long-term survival and growth in environments outside the host. As the extraintestinal physical and chemical conditions are often different from those within the host, it is possible that distinct genetic adapta...

The general stress resistance of Escherichia coli is controlled by the RpoS sigma factor (phi(S)), but mutations in rpoS are surprisingly common in natural and laboratory populations. Evidence for the selective advantage of losing rpoS was obtained from experiments with nutrient-limited bacteria at different growth rates. Wild-type bacteria were rapidly displaced by rpoS mutants in both glucose...

The RpoN-RpoS regulatory pathway plays a central role in governing adaptive changes by B. burgdorferi when the pathogen shuttles between its tick vector and mammalian hosts. In general, transcriptional activation of bacterial RpoN (σ54)-dependent genes requires an enhancer binding protein. B. burgdorferi encodes the putative enhancer binding protein Rrp2. Previous studies have revealed that the...

The Erwinia amylovora rpoS gene, encoding the alternative sigma factor RpoS, has been cloned and characterized. Though highly sensitive to a number of environmental stresses, an E. amylovora rpoS mutant was not compromised in its ability to grow or cause disease symptoms within apple seedlings or in an overwintering model.

The sigma factor RpoS regulates the expression of many stress response genes and is required for virulence in several bacterial species. We now report that RpoS accumulates when Salmonella enterica serovar Typhimurium is growing logarithmically in media with low Mg(2+) concentrations. This process requires the two-component regulatory system PhoP/PhoQ, which is specifically activated in low Mg(...

The RpoS sigma factor protein of Escherichia coli RNA polymerase is the master transcriptional regulator of physiological responses to a variety of stresses. This stress response comes at the expense of scavenging for scarce resources, causing a trade-off between stress tolerance and nutrient acquisition. This trade-off favors non-functional rpoS alleles in nutrient-poor environments. We used e...

The mechanisms by which Escherichia coli cells survive exposure to the toxic electrophile N-ethylmaleimide (NEM) have been investigated. Stationary-phase E. coli cells were more resistant to NEM than exponential-phase cells. The KefB and KefC systems were found to play an important role in protecting both exponential- and stationary-phase cells against NEM. Additionally, RpoS and the DNA-bindin...

Laboratory strains and natural isolates of Escherichia coli differ in their level of stress resistance due to strain variation in the level of the sigma factor sigma(S) (or RpoS), the transcriptional master controller of the general stress response. We found that the high level of RpoS in one laboratory strain (MC4100) was partially dependent on an elevated basal level of ppGpp, an alarmone res...