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Salmonella Typhimurium: Heat-shocked cells vs. control cells and acid-shocked cells vs. control cells

ABSTRACT: We investigated if the transcriptional response of S. Typhimurium to temperature and acid variations was hysteretic and showed memory, i.e., if the transcriptional regulation caused by environmental stimuli remained after the stimuli ceased. The transcriptional activity of non-replicating stationary-phase cells of Salmonella Typhimurium caused by the exposure to 45°C and to pH 5 for 30 min was monitored by microarray hybridizations before the application of the stress and at the end of the treatment period, as well as immediately and 30 minutes after conditions were set back to their initial values, 25°C and pH 7, respectively. We also investigated if hysteresis was accompanied with higher resistance to inactivation conditions, 50°C and/or pH 3, as well as more efficient growth at extreme conditions, 43°C and/or pH 4.5.

ORGANISM(S): Salmonella enterica subsp. enterica serovar Typhimurium str. SL1344 Salmonella enterica subsp. enterica serovar Typhimurium

PROVIDER: GSE37636 | GEO | 2012/05/20

SECONDARY ACCESSION(S): PRJNA163643

REPOSITORIES: GEO

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Project description:Staphylococcus aureus is a leading cause of hospital- and community-associated infections. The organism’s ability to cause disease can, in part, be attributable to its ability to adapt to otherwise deleterious host-associated stresses. Like other bacterial species, the modulation of mRNA turnover appears to play an important role in S. aureus adaptation to certain environmental stresses. In the current study Affymetrix GeneChips® were used to examine the S. aureus responses to acid and alkaline shock-inducing conditions and to assess whether stress dependent changes in mRNA turnover are likely to facilitate the organism’s ability to tolerate extreme pH challenge. Results indicate that S. aureus adapts to pH shock by eliciting responses expected of organisms coping with pH alteration, including neutralizing cellular internal pH, DNA repair, amino acid biosynthesis and virulence factor expression. Further, it was found that the cellular response to alkaline conditions elicits a transcriptional profile that is similar to that of stringent response induced cells. Consistent with that observation, we show that the activator of the stringent response, (p)ppGpp, levels are profoundly elevated during alkaline shock conditions. We also show that the mRNA turnover properties of acid or alkaline shocked cells significantly differ from that of cells grown at neutral pH. A comparison of the mRNA degradation properties of transcripts whose titers either increased or decreased in response to sudden pH change revealed that alterations in mRNA degradation may, in part, account for the changes in the mRNA levels of factors predicted to mediate pH tolerance. Finally, a set of small stable RNA molecules were induced in response to acid or alkaline shock conditions. As in other organisms, these molecules may mediate mRNA stability and adaptation to otherwise deleterious growth conditions. Staphylococcus aureus strain UAMS-1 was grown to exponential phase and either mock treated (pH maintained at 7.4) or subjected to acid (pH 4)- or alkaline (pH 10) conditions for 30 min. Next, 200 micrograms per ml of rifampicin were added to arrest transcript synthesis. RNA was extracted from cell suspensions at 0, 2.5, 5, 15, and 30 min post-transcriptional arrest, labeled and hybridized to S. aureus GeneChips. A comparison of 0 min samples allowed assessment of acid and alkaline shock responses. A comparison of 0 min to that of various post-transcriptional arrest RNA samples allowed assessment of the mRNA turnover properties of mock vs acid or alkaline shocked cells. Duplicates of each experimental condition and corresponding post-transcriptional arrest time point were used (biological replicates).

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Salmonella Typhimurium: Heat-shocked cells vs. control cells and acid-shocked cells vs. control cells

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