Microarray-Based Analysis of theStaphylococcus aureusσ^BRegulon

Abstract

Microarray-based analysis of the transcriptional profiles of the genetically distinct Staphylococcus aureus strains COL, GP268, and Newman indicate that a total of 251 open reading frames (ORFs) are influenced by B activity. While B was found to positively control 198 genes by a factor of >2 in at least two of the three genetic lineages analyzed, 53 ORFs were repressed in the presence of B . Gene products that were found to be influenced by B are putatively involved in all manner of cellular processes, including cell envelope biosynthesis and turnover, intermediary metabolism, and signaling pathways. Most of the genes and/or operons identified as upregulated by B were preceded by a nucleotide sequence that resembled the B consensus promoter sequence of Bacillus subtilis. A conspicuous number of virulence-associated genes were identified as regulated by B activity, with many adhesins upregulated and prominently represented in this group, while transcription of various exoproteins and toxins were repressed. The data presented here suggest that the B of S. aureus controls a large regulon and is an important modulator of virulence gene expression that is likely to act conversely to RNAIII, the effector molecule of the agr locus. We propose that this alternative transcription factor may be of importance for the invading pathogen to fine-tune its virulence factor production in response to changing host environments.Transcription of DNA into RNA is catalyzed by RNA polymerase. In bacteria, one RNA polymerase generates nearly all cellular RNAs, including ribosomal, transfer, and mRNA. This enzyme consists of six subunits, ␣ 2 ␤␤Ј, with ␣ 2 ␤␤Ј forming the catalytically competent RNA polymerase core enzyme (E). The core is capable of elongation and termination of transcription, but it is unable to initiate transcription at specific promoter sequences. The subunit, which when bound to E forms the holoenzyme (E-), directs the multisubunit complex to specific promoter elements and allows efficient initiation of transcription (reviewed in references 5 and 6). Therefore, factors provide an elegant mechanism in eubacteria to allow simultaneous transcription of a variety of genetically unlinked genes, provided all of these genes share the same promoter specificities.In addition to the housekeeping sigma subunit, 70 or A , most bacteria produce one or more additional subunits, termed alternative factors, which direct the respective Ecomplex to distinct classes of promoters that contain alternative factor-specific sequences. Alternative factors have been shown in various bacteria to be of importance for survival under extreme conditions (7,14,23,31,38,44,49,60,68,73,78,79,80) and to influence virulence and pathogenicity (8,13,32,35,37,42,51,57,61,71,75,78,81).At least six alternative factors are produced by the enteric bacterium Escherichia coli (reviewed in reference 6). Genomic sequence analysis suggests that many alternative factors also exist in a number of other pathogenic species such as Treponema palladium (4 alternative f...

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