Project description:The alternative sigma factor M-OM-^CB 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 M-OM-^CB promoter sequences, or indirectly via M-OM-^CB-dependent elements. The M-OM-^CB-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 M-OM-^CB inactivation, indicating that both regulons do only partially overlap, despite the M-OM-^CB dependency of the yabJ-spoVG expression. Thus, M-OM-^CB 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 M-OM-^CB-dependent regulation of a subset of virulence factors by antagonizing the M-OM-^CB effect. Newman wild type strain compared to double mutant spoVG and yabJ or to sigB truncated mutant
Project description:The purpose of this study was to compare the global, growth phase-dependent transcriptional profiles of two isolates of Staphylococcus aureus. One isolate is a prototypic laboratory strain named RN6390, and has been used frequently as a model organism for study of staphylococcal physiology and virulence. However, recent studies indicate that RN6390 is not, in general, genotypically or phenotypically representative of clinical isolates of Staphyloccos aureus. Therefore, there is no current comprehensive picture of gene expression patterns in a virulent, clinical isolate of Staphyloccous aureus. For these reasons, we compare the transcriptional profile of RN6390 to that of a virulent clinical isolate, UAMS-1. Also included in this study is profiling of two UAMS-1 regulatory mutants, UAMS-155, and UAMS-929. These strains possess mutations in the accessory gene regulator (agr) and staphylococcal accessory regulator (sarA) genes, respectively. These two genes are well described global regulatory molecules that are reported to play important roles in controlling virulence factor production and biofilm formation in Staphylococcus aureus. However, most study of these two molecules has been limited to laboratory strains such as RN6390. For these reasons, this study also includes transcriptional profiling of UAMS agr and sarA mutants. Keywords: Comparative, growth phase-dependent transcriptional profiling of bacterial strains and isogenic regulatory mutants
