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Series GSE7492

Query DataSets for GSE7492

Status

Public on Nov 29, 2007

Title

Listeria monocytogenes and Listeria innocua SigB Regulons as defined by salt-stressed and early stationary-phase cells

Organisms

Listeria monocytogenes; Listeria innocua

Experiment type

Expression profiling by array

Summary

In several gram-positive bacterial genera including Bacillus, Staphylococcus, and Listeria, sigma B (σB) has been identified as a stress-responsive alternative sigma factor responsible for initiating transcription of genes (the σB regulon) involved in response to stress-inducing environmental conditions. In L. monocytogenes, a foodborne pathogen of considerable threat to public health and the food industry, σB is involved in regulation of stress response and virulence gene expression. We have defined the σB regulon in L. monocytogenes during early stationary phase and under salt stress (0.3M NaCl) conditions using whole-genome microarrays, identifying 168 genes that generated ≥2.0-fold higher signals in the parental strain 10403S than in an isogenic sigB null mutant (ΔsigB), categorized into nine functional groups including stress-response genes (12), virulence genes (5), and genes related to transport (26) and metabolism (45). To gain a broader biological perspective of the σB stress response system, we applied these microarrays to Listeria innocua under the same environmental conditions. Our studies revealed 64 candidates in the L. innocua σB regulon with ≥2.0-fold higher signals in the parent than in a ΔsigB mutant; 49 of the 64 genes overlap with the L. monocytogenes σB regulon, indicating extensive overlap in σB-controlled genes between the two species. Further transcriptional analysis using TaqMan quantitative real time RT-PCR was performed for selected genes that displayed contrasting fold changes among the four microarray data sets (two stress conditions per species). We report novel members of the L. monocytogenes σB regulon, as well as the initial definition of the L. innocua σB regulon. Our comparative studies of the σB stress response systems in L. monocytogenes and L. innocua revealed features of the σB regulon that are conserved and unique to the two species.
Keywords: Listeria monocytogenes, Listeria innocua, SigB regulon, salt stress, stationary phase

Overall design

Independent RNA isolations were performed for each growth experiment (log phase cells exposed to BHI+0.3M NaCl and early stationary phase cells). Three biological replicates were used in competitive whole-genome microarray experiments. For each set of hybridizations (salt-stressed and early stationary phase), RNA from the parent strain L. monocytogenes 10403S were hybridized to RNA from the isogenic sigB null mutant.

Contributor(s)

Raengpradub S, Wiedmann M, Boor KJ

Citation(s)

18024685

Submission date

Apr 10, 2007

Last update date

Mar 17, 2012

Contact name

Sarita Raengpradub

E-mail(s)

sr266@cornell.edu