Effect of cortisol on S. Typhimurium parental strain and an isogenic scsA mutant
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ABSTRACT:
ORGANISM(S): Salmonella enterica subsp. enterica serovar Typhimurium
SUBMITTER: Arthur Thompson
PROVIDER: E-GEOD-55430 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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Project description:The expression profile of an S. Typhimurium hfq mutant-strain was compared to the parental strain under 2 different growth conditions; early stationary phase and SPI-1 (Salmonella pathogenicity island 1) inducing condition. Keywords: Genetic modification This study comprises two separate experiments performed under different growth conditions, were the gene expression profile was compared to that of the parental strain. Three biological replicates were performed for each strain and condition. For this study, we used Salmonella genomic DNA as the comparator which also acted as the control for spot quality.
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2011-07-25 | E-GEOD-30923 | biostudies-arrayexpress
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Project description:The expression profile of an S. Typhimurium mutant strain unable to synthesise ppGpp (relAspoT deletions) was compared to the wild-type strain. The effect of ppGpp on virulence gene expression was studied under 4 different growth conditions that induce virulence gene expression. Keywords: genetic modification Study comprised 4 separate experiments (with 2 strains and 4 replicates for each strain per growth condition). The experiments were indirect comparisons using Salmonella genomic DNA as the comparator which also acted as the control for spot quality.
2010-06-11 | E-GEOD-4631 | biostudies-arrayexpress
Project description:It is well established that small noncoding RNAs (sRNAs) of bacteria recognize the 5â?? regions of target mRNAs, generally at the ribosome binding site. Until now, the translated coding sequence (CDS) of mRNA appeared to be refractory to sRNA interactions. We have discovered that Salmonella MicC RNA silences ompD mRNA by targeting the CDS, at codons 23-26. Analyses of MicC-ompD RNA complexes in vitro, and of chimeric sRNAs and ompD reporter fusions in vivo, show that interactions are confined to the CDS, and that a â?¤12 bp RNA duplex involving the conserved 5â?? end of MicC is essential and sufficient for target repression. MicC cannot act as a translational repressor at this downstream position being unable to inhibit 30S or 70S ribosome activity on the ompD mRNA. Instead, MicC accelerates RNase E-dependent ompD mRNA decay. The degradosome contributes to target destabilization, and facilitates the efficient degradation of processed ompD mRNA. Our data show that bacterial gene silencing by sRNAs can take place downstream of the translational initiation site by triggering irreversible mRNA decay. This ability of sRNAs allows targets in the CDS to be silenced without interference from the strong RNA helicase activity of elongating ribosomes. To determine the targets of the small regulatory RNA MicC in S. Typhimurium, we looked at the effect of a short pulse of MicC over-expression on the Salmonella transcriptome. To achieve over-expression, the micC gene was cloned in the pBAD plasmid and induced with 0.2% L-arabinose for 10 min. We then extracted the total RNA for transcriptional profiling. A strain carrying the pBAD plasmid w/o insert was used as negative control. 3 biological replicates were performed. This sRNA target identification strategy has been described in Papenfort et al; Molecular Microbiology (2006) 62(6), 1674â??1688.
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Project description:StpA is a paralogue of the nucleoid associated protein H-NS that is conserved in a range of enteric bacteria and had no known function in Salmonella enterica serovar Typhimurium. Here, we show that 5% of the Salmonella genome is regulated by StpA, which contrasts with the situation in Escherichia coli where deletion of stpA only had minor effects on gene expression. The StpA-dependent genes of S. Typhimurium are a specific subset of the H-NS regulon that are predominantly under the positive control of sigma38 (RpoS), CRP-cAMP and PhoP. The regulatory role of StpA varied at different growth phases; StpA only controlled sigma38 levels at mid-exponential phase when it prevented inappropriate activation of sigma38 during rapid bacterial growth. In contrast, StpA only activated the CRP-cAMP regulon during late exponential phase. The effect of stpA deletion on S. Typhimurium gene expression during growth in LB was analysed at 4 different time points (early-log, mid-log, late-log, and stationary phase) where the gene expression profile of the stpA-deletion strain was compared to that of the parental strain. Between two and three biological replicates were performed for each strain and time point. For this study, we used Salmonella genomic DNA as the comparator which also acted as the control for spot quality.
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