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σB-dependent yabJ-spoVG operon involved in regulation of extracellular nuclease, lipase and protease expression in Staphylococcus aureus

ABSTRACT: The alternative sigma factor σB of Staphylococcus aureus is involved in the coordination of the general stress response, expression of virulence determinants and modulation of antibiotic resistance levels. It controls a large regulon, either directly by recognizing conserved σB promoter sequences, or indirectly via σB-dependent elements. The σB-controlled yabJ-spoVG operon encodes two such putative downstream elements. We report here transcriptome analysis in S. aureus Newman showing that inactivation of the yabJ-spoVG operon had primarily a repressing effect on a small subregulon comprising mainly virulence factors, including a nuclease (nuc), a protease (splE) and a lipase (lip).. As a consequence extracellular nuclease, protease and lipase activities were reduced in a yabJspoVG mutant. Trans-complementation by SpoVG was sufficient to restore their reduced phenotypic expression and lowered transcription due to yabJ-spoVG deletion. It did not restore, however, the changes triggered by σB inactivation, indicating that both regulons do only partially overlap, despite the σB dependency of the yabJ-spoVG expression. Thus, σB is likely to control additional, SpoVG-independent factors affecting the expression of numerous hydrolytic enzymes. SpoVG, on the other hand, seems to fine-tune the σB-dependent regulation of a subset of virulence factors by antagonizing the σB effect.

ORGANISM(S): Staphylococcus aureus subsp. aureus MRSA252 Staphylococcus aureus subsp. aureus N315 Staphylococcus aureus subsp. aureus COL Staphylococcus aureus subsp. aureus Mu50 Staphylococcus aureus Staphylococcus aureus subsp. aureus NCTC 8325 Staphylococcus aureus subsp. aureus USA300 Staphylococcus aureus subsp. aureus MW2 Staphylococcus aureus subsp. aureus MSSA476

PROVIDER: GSE30115 | GEO | 2011/11/23

SECONDARY ACCESSION(S): PRJNA144047

REPOSITORIES: GEO

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Project description: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

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σB-dependent yabJ-spoVG operon involved in regulation of extracellular nuclease, lipase and protease expression in Staphylococcus aureus

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