The influence of SaeRS and σ(B) on the expression of superantigens in different Staphylococcus aureus isolates

Staphylococcus aureus is a major human pathogen. Superantigens (SAg) are important virulence factors in S. aureus, but the regulation of SAg gene expression is largely unknown. Using 2 sequenced S. aureus strains (COL and Newman) and 4 clinical isolates, regulation of gene expression was investigate...

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Bibliographic Details
Published in:International journal of medical microbiology 2011-08, Vol.301 (6), p.488-499
Main Authors: Kusch, Kathrin, Hanke, Kirsten, Holtfreter, Silva, Schmudde, Mareike, Kohler, Christian, Erck, Christian, Wehland, Jürgen, Hecker, Michael, Ohlsen, Knut, Bröker, Barbara, Engelmann, Susanne
Format: Article
Language:English
Subjects:
Bacterial Proteins - genetics
Bacterial Proteins - metabolism
Cell Proliferation
Cells, Cultured
Enterotoxins - genetics
Enterotoxins - metabolism
Gene Expression Regulation, Bacterial
Genes, Bacterial
Humans
Mutation
Operon
Polymerase Chain Reaction
Promoter Regions, Genetic
Protein Kinases
RNA, Bacterial - genetics
RNA, Bacterial - metabolism
Sigma Factor - genetics
Sigma Factor - metabolism
Staphylococcus aureus - classification
Staphylococcus aureus - genetics
Staphylococcus aureus - isolation & purification
Superantigens - genetics
Superantigens - metabolism
Transcription Factors
Transcription, Genetic
Virulence Factors - genetics
Virulence Factors - metabolism
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Summary:Staphylococcus aureus is a major human pathogen. Superantigens (SAg) are important virulence factors in S. aureus, but the regulation of SAg gene expression is largely unknown. Using 2 sequenced S. aureus strains (COL and Newman) and 4 clinical isolates, regulation of gene expression was investigated in more detail for 12 SAgs. The SAg-encoding genes were expressed in a growth phase-dependent manner: while the egc operon was mainly transcribed at low optical densities, the transcription of seb was induced at high optical densities. The transcript levels of sea, sek, seq, sep, and tst-1 did not change significantly during growth. The T cell-mitogenic activity of supernatants correlated with the transcription data. SaeRS and σ(B) strongly influenced SAg gene transcription. σ(B) activated transcription of seh, tst-1, and of the egc operon. A possible σ(B)-dependent promoter was identified in front of the egc operon. In contrast, a loss of σ(B) enhanced the transcript level of seb, suggesting an indirect effect of the alternative sigma factor on the transcription of this gene. Transcriptional studies of an saeS mutant showed that the two-component system only activates transcription of seb. The influence of σ(B) and SaeRS on the expression of SAg genes was validated by T cell proliferation assays. For sigB mutants in different strains, different effects on the T cell-mitogenic potential were observed depending on the SAg gene repertoire of the isolates.
ISSN:1618-0607
DOI:10.1016/j.ijmm.2011.01.003