<i>rpoS</i>
            Mutants in Archival Cultures of
            <i>Salmonella enterica</i>
            Serovar Typhimurium

Sutton, Amy; Buencamino, Raphael; Eisenstark, A.

doi:10.1128/jb.182.16.4375-4379.2000

Cited by 60 publications

(54 citation statements)

References 26 publications

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“…Although rpoS allelic variation has been demonstrated in archival cultures of Salmonella (36,41,42,46), there is little information available concerning the presence of mutant rpoS alleles in clinical isolates of Salmonella. Jordan et al (20) examined rpoS variability in 18 environmental isolates of different serotypes of salmonellae by single-strand conformation polymorphism analysis.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, mutant rpoS alleles have been detected in clinical isolates of Shiga-like toxin-producing E. coli (45) and in natural isolates of enterohemorrhagic E. coli O157:H7 (38). rpoS allelic variation has also been observed in highly passaged laboratory strains of Salmonella (36,41,42,46). However, little information is available concerning the presence of mutant rpoS alleles in clinical isolates of Salmonella (20,21).…”

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confidence: 99%

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Characterization of the RpoS Status of Clinical Isolates of Salmonella enterica

Robbe‐Saule

Algorta

Rouilhac

et al. 2003

Appl Environ Microbiol

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The stationary-phase-inducible sigma factor, S (RpoS), is the master regulator of the general stress response in Salmonella and is required for virulence in mice. rpoS mutants can frequently be isolated from highly passaged laboratory strains of Salmonella. We examined the rpoS status of 116 human clinical isolates of Salmonella, including 41 Salmonella enterica serotype Typhi strains isolated from blood, 38 S. enterica serotype Typhimurium strains isolated from blood, and 37 Salmonella serotype Typhimurium strains isolated from feces. We examined the abilities of these strains to produce the S protein, to express RpoS-dependent catalase activity, and to resist to oxidative stress in the stationary phase of growth. We also carried out complementation experiments with a cloned wild-type rpoS gene. Our results showed that 15 of the 41 Salmonella serotype Typhi isolates were defective in RpoS. We sequenced the rpoS allele of 12 strains. This led to identification of small insertions, deletions, and point mutations resulting in premature stop codons or affecting regions 1 and 2 of S , showing that the rpoS mutations are not clonal. Thus, mutant rpoS alleles can be found in freshly isolated clinical strains of Salmonella serotype Typhi, and they may affect virulence properties. Interestingly however, no rpoS mutants were found among the 75 Salmonella serotype Typhimurium isolates. Strains that differed in catalase activity and resistance to hydrogen peroxide were found, but the differences were not linked to the rpoS status. This suggests that Salmonella serotype Typhimurium rpoS mutants are counterselected because rpoS plays a role in the pathogenesis of Salmonella serotype Typhimurium in humans or in the transmission cycle of the disease.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Characterization of the RpoS Status of Clinical Isolates of Salmonella enterica

Robbe‐Saule

Algorta

Rouilhac

et al. 2003

Appl Environ Microbiol

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“…The other isolates, Sarc4 and Sarc16, were identified as being RpoS deficient. Mutations in rpoS have been detected in other Salmonella isolates and are thought to reflect either natural variation or laboratory-induced changes (34,47,60).…”

Section: Discussionmentioning

confidence: 99%

Comparative Genetics of the rdar Morphotype inSalmonella

White¹,

Surette

2006

J Bacteriol

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The Salmonella rdar morphotype is a distinct, rough and dry colony morphology formed by the extracellular interaction of thin aggregative fimbriae (Tafi or curli), cellulose, and other polysaccharides. Cells in rdar colonies are more resistant to desiccation and exogenous stresses, which is hypothesized to aid in the passage of pathogenic Salmonella spp. between hosts. Here we analyzed the genetic and phenotypic conservation of the rdar morphotype throughout the entire Salmonella genus. The rdar morphotype was conserved in 90% of 80 isolates representing all 7 Salmonella groups; however, the frequency was only 31% in a reference set of 16 strains (Salmonella reference collection C [SARC]). Comparative gene expression analysis was used to separate cis-and trans-acting effects on promoter activity for the 16 SARC strains, focusing on the 780-bp intergenic region containing divergent promoters for the master regulator of the rdar morphotype (agfD) and the Tafi structural genes (agfB). Surprisingly, promoter functionality was conserved in most isolates, and loss of the phenotype was due primarily to defects in trans-acting regulatory factors. We hypothesize that trans differences have been caused by domestication, whereas cis differences, detected for Salmonella enterica subsp. arizonae isolates, may reflect an evolutionary change in lifestyle. Our results demonstrate that the rdar morphotype is conserved throughout the salmonellae, but they also emphasize that regulation is an important source of variability among isolates.

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“…There are also numerous physiological and regulatory differences between MG1655 and another commonly used K-12 lineage, MC4100 (King et al, 2004). Stored archival cultures of bacteria can be heterogeneous (Sutton et al, 2000), which is also likely to contribute to strain variation in stocks of K-12 strains. We are interested in the molecular basis of strain variation and in this study identify some of the factors important not only in strain differences but also in the settings for global gene regulation in bacteria.…”

Section: Introductionmentioning

confidence: 99%

Strain variation in ppGpp concentration and RpoS levels in laboratory strains of Escherichia coli K-12

Spira

Ferenci

2008

Microbiology

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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 s 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 responding to stress and starvation. The elevated ppGpp was caused by two mutations in spoT, a gene associated with ppGpp synthesis and degradation. The nature of the spoT allele influenced the level of ppGpp in both MC4100 and another commonly used K-12 strain, MG1655. Introduction of the spoT mutation into MG1655 also resulted in an increased level of RpoS, but the amount of RpoS was lower in MG1655 than in MC4100 with either the wild-type or mutant spoT allele. In both MC4100 and MG1655, high ppGpp concentration increased RpoS levels, which in turn reduced growth with poor carbon sources like acetate. The growth inhibition resulting from elevated ppGpp was relieved by rpoS mutations. The extent of the growth inhibition by ppGpp, as well as the magnitude of the relief by rpoS mutations, differed between MG1655 and MC4100. These results together suggest that spoT mutations represent one of several polymorphisms influencing the strain variation of RpoS levels. Stress resistance was higher in strains with the spoT mutation, which is consistent with the conclusion that microevolution affecting either or both ppGpp and RpoS can reset the balance between self-protection and nutritional capability, the SPANC balance, in individual strains of E. coli.

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rpoS Mutants in Archival Cultures of Salmonella enterica Serovar Typhimurium

Cited by 60 publications

References 26 publications

Characterization of the RpoS Status of Clinical Isolates of Salmonella enterica

Characterization of the RpoS Status of Clinical Isolates of Salmonella enterica

Comparative Genetics of the rdar Morphotype inSalmonella

Strain variation in ppGpp concentration and RpoS levels in laboratory strains of Escherichia coli K-12

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