Regulation of agr -Dependent Virulence Genes in Staphylococcus aureus by RNAIII from Coagulase-Negative Staphylococci

Abstract

Many of the genes coding for extracellular toxins, enzymes, and cell surface proteins in Staphylococcus aureus are regulated by a 510-nucleotide (nt) RNA molecule, RNAIII. Transcription of genes encoding secreted toxins and enzymes, includinghla (alpha-toxin), saeB (enterotoxin B),tst (toxic shock syndrome toxin 1), and ssp(serine protease), is stimulated, while transcription of genes encoding cell surface proteins, like spa (protein A) andfnb (fibronectin binding proteins), is repressed. Besides being a regulator, RNAIII is also an mRNA coding for staphylococcal delta-lysin. We have identified RNAIII homologs in three different coagulase-negative staphylococci (CoNS), i.e., Staphylococcus epidermidis, Staphylococcus simulans, andStaphylococcus warneri. RNAIII from these CoNS turned out to be very similar to that of S. aureus and contained open reading frames encoding delta-lysin homologs. Though a number of big insertions and/or deletions have occurred, mainly in the 5′ half of the molecules, the sequences show a high degree of identity, especially in the first 50 and last 150 nt. The CoNS RNAIII had the ability to completely repress transcription of protein A in an RNAIII-deficientS. aureus mutant and the ability to stimulate transcription of the alpha-toxin and serine protease genes. However, the stimulatory effect was impaired compared to that of S. aureus RNAIII, suggesting that these regulatory functions are independent. By creating S. epidermidis-S. aureus RNAIII hybrids, we could also show that both the 5′ and 3′ halves of the RNAIII molecule are involved in the transcriptional regulation of alpha-toxin and serine protease mRNAs in S. aureus.

Autoinduction and signal transduction in the regulation of staphylococcal virulence

“…It has a complex secondary structure (Benito et al, 2000; see Fig. 4), which is well conserved (although the sequence is not) among several staphylococcal species (Benito et al, 1998;Tegmark et al, 1998), resulting in interspecific cross-reactivity of the molecule. RNA III acts reciprocally, upregulating transcription of most of the extracellular protein genes and downregulating that of many surface protein genes (Novick et al, 1993;Saravia-Otten et al, 1997).…”

Development of a skin colonization model in gnotobiotic piglets for the study of the microbial ecology of meticillin-resistant Staphylococcus aureus ST398

“…xylosus have been reported to produce an RNAIIIinhibiting peptide (Balaban et al 2000(Balaban et al , 2001 that inhibited RNAIII synthesis and virulence signalling pathways in vitro and in vivo and infection by Staph. aureus (Tegmark et al 1998;Mayville et al 1999;Cirioni et al 2007). During the current study, bacterial counts increased similarly for both MRSA and CNS from inoculation (days 14 and 16) until day 32, indicating that colonization by MRSA during this period may be unaffected by prior or subsequent inoculation of maternal staphylococcal flora.…”

Microbes and the Inflammatory Response in Necrotising Enterocolitis

“…CoNS were identified using API ID-32 STAPH strips (bioMérieux). PCR primers for the δ-toxin gene were based on sequence data published by Tegmark et al and PCR conditions were as described by McIntosh [70,71]. Cell-free culture supernatants of the CoNS isolates and a δ-toxin producing S. aureus control were tested for cell damage (cytopathic effect; CPE) against the small and large intestinal tissue culture cell lines, Caco2 and HT29 [70].…”