Like many eukaryotes, bacteria make widespread use of postreplicative DNA methylation for the epigenetic control DNA-protein interactions. Unlike however, adenine (rather than cytosine methylation) as an signal. plays roles in virulence diverse pathogens humans and livestock animals, including pathogenic Escherichia coli, Salmonella, Vibrio, Yersinia, Haemophilus, Brucella. In Alphaproteobacteria, at GANTC sites by CcrM methylase regulates cell cycle couples gene transcription to...

Significance The ability of bacteria to survive antibiotic challenge without mutation (a phenomenon known as “adaptive resistance”) has been traditionally viewed the consequence bacterial responses environmental cues. This study shows that adaptive resistance can also occur in absence stimuli. Cell-to-cell fluctuations critical physiological traits preadapt certain cells within an isogenic culture lethal selection, and growth “lucky” survivors generates subpopulations with increased...

Mutants of Salmonella typhimurium lacking DNA adenine methylase are attenuated for virulence in BALB/c mice. LD 50 values a methylation (Dam) − mutant at least 10 3 - to 4 -fold higher than those the parental strain when administrated by oral or intraperitoneal routes. Dam mutants unable proliferate target organs but persist low numbers these locations. Efficient protection challenge with virulent is observed mice infected mutant. Use ileal loop assay shows that less cytotoxic M cells and...

Bile possesses antibacterial activity because bile salts disrupt membranes, denature proteins, and damage DNA. This study describes mechanisms employed by the bacterium Salmonella enterica to survive bile. Sublethal concentrations of salt sodium deoxycholate (DOC) adapt lethal Adaptation seems be associated multiple changes in gene expression, which include upregulation RpoS-dependent general stress response other responses. The crucial role adaptation is supported observation that RpoS(-)...

The Salmonella enterica opvAB operon is a horizontally-acquired locus that undergoes phase variation under Dam methylation control. OpvA and OpvB proteins form intertwining ribbons in the inner membrane. Synthesis of alters lipopolysaccharide O-antigen chain length confers resistance to bacteriophages 9NA (Siphoviridae), Det7 (Myoviridae), P22 (Podoviridae). These phages use as receptor. Because variation, S. cultures contain subpopulations opvABOFF opvABON cells. In presence bacteriophage...

In all living cells, genomic DNA is compacted through interactions with dedicated proteins and/or the formation of plectonemic coils. bacteria, compaction achieved dynamically, coordinated dense and constantly changing transcriptional activity. H-NS, a major bacterial nucleoid structuring protein, special interest due to its interplay RNA polymerase. H-NS:DNA nucleoprotein filaments inhibit transcription initiation by However, discovery that genes silenced H-NS can be activated originating...

ABSTRACT Salmonella enterica serovar Typhimurium proliferates within cultured epithelial and macrophage cells. Intracellular bacterial proliferation is, however, restricted normal fibroblast To characterize this phenomenon in detail, we investigated the possibility that pathogen itself might contribute to attenuating intracellular growth rate. S . mutants were selected rat kidney fibroblasts displaying an increased These harbored loss-of-function mutations virulence-related regulatory genes...

All enzymes are able to use alternative substrates. When these naturally occurring metabolites, an 'underground reaction' takes place. Examples presented in which underground metabolism of this sort produces observable phenotype. Although biological processes can be remarkably accurate, evolution has selected error rates far from perfect. It is suggested here that a certain level metabolic inaccuracy, addition saving energy, may also confer evolutionary advantage, for example by providing...

Summary Ubiquitous RNA‐binding protein Hfq mediates the regulatory activity of many small RNAs (sRNAs) in bacteria. To identify potential targets for Hfq‐mediated regulation Salmonella , we searched lacZ translational fusions whose varied presence or absence Hfq. Fusions downregulated by were more common than showing opposite response. Surprisingly, a subset isolates from major class, higher was due to transcriptional activation alternative sigma factor RpoE (σ E ). Activation σ regulon...

Abstract In the absence of DNA adenine methylase, growth Salmonella enterica serovar Typhimurium is inhibited by bile. Mutations in any mutH, mutL, and mutS genes suppress bile sensitivity a Dam− background, indicating that an active MutHLS system renders mutants sensitive. However, inactivation does not cause sensitivity. An analogy with Escherichia coli, which sensitizes to DNA-injuring agents, suggested might damage. support this hypothesis, we show induces SOS response S. increases...

Exposure of Salmonella enterica to sodium cholate, deoxycholate, chenodeoxycholate, glycocholate, taurocholate, or glycochenodeoxycholate induces the SOS response, indicating that DNA-damaging activity bile resides in salts. Bile increases frequency GC --> AT transitions and expression genes belonging OxyR SoxRS regulons, suggesting salts may cause oxidative DNA damage. S. mutants lacking both exonuclease III (XthA) endonuclease IV (Nfo) are sensitive, requires base excision repair (BER)...

ABSTRACT Transcriptomic analyses during growth in Luria-Bertani medium were performed strain SL1344 of Salmonella enterica serovar Typhimurium and two isogenic derivatives lacking Dam methylase. More genes repressed than activated by methylation (139 versus 37). Key that differentially regulated verified independently. The largest classes Dam-repressed included belonging to the SOS regulon, as previously described Escherichia coli , SOS-inducible prophages ST64B, Gifsy-1, Fels-2....

Summary Prokaryotic regulatory small RNAs act by a conserved mechanism and yet display stunning structural variability. In the present study, we used mutational analysis to dissect functional anatomy of RybB, σ E ‐dependent sRNA that regulates synthesis major porins in Escherichia coli Salmonella . Mutations chromosomal rybB locus altered expression an ompC – lac fusion were identified. Some mutations cluster within seven‐nucleotide segment at 5′ end affect its ability pair with sequence 40...

Significance Horizontal gene transfer is a major force in bacterial evolution, and widespread mechanism involves conjugative plasmids. Albeit potentially beneficial at the population level, plasmid burden for individual cells. Therefore, assembly of conjugation machinery strictly controlled, especially under stress. Here, we describe an RNA-based regulatory circuit host–plasmid communication where RNA (RprA) inhibits through posttranscriptional activation two genes. Because one activated...

We report the first investigation of binding Salmonella enterica LeuO LysR-type transcription regulator to its genomic targets in vivo. Chromatin-immunoprecipitation-on-chip identified 178 sites on chromosome S. serovar Typhimurium strain SL1344. These were distributed across both core and horizontally acquired genome, included housekeeping genes known contribute virulence. Sixty-eight co-bound by global repressor protein, H-NS. Thus, while may function as an H-NS antagonist, these functions...