The virR/virS locus regulates the transcription of genes encoding extracellular toxin production in Clostridium perfringens

Abstract

Extracellular toxin production in Clostridium perfringens is positively regulated by the two-component regulatory genes virR and virS. Northern (RNA) blots carried out with RNA preparations from the wild-type strain 13 and the isogenic virR and virS mutants TS133 and JIR4000 showed that the virR and virS genes composed an operon and were transcribed as a single 2.1-kb mRNA molecule. Primer extension analysis led to the identification of two promoters upstream of virR. Hybridization analysis of the mutants and their complemented derivatives showed that the virR/virS system positively regulated the production of alpha-toxin (or phospholipase C), theta-toxin (perfringolysin O), and kappa-toxin (collagenase) at the transcriptional level. However, the modes of regulation of these genes were shown to differ. The theta-toxin structural gene, pfoA, had both a major and a very minor promoter, with the major promoter being virR/virS dependent. The colA gene, which encodes the kappa-toxin, had two major promoters, only one of which was virR/virS-dependent. In contrast, the alpha-toxin structural gene, plc, had only one promoter, which was shown to be partially regulated by the virR and virS genes. Comparative analysis of the virR/virS-dependent promoters did not reveal any common sequence motifs that could represent VirR-binding sites. It was concluded that either the virR/virS system modulates its effects via secondary regulatory genes that are specific for each toxin structural gene or the VirR protein does not have a single consensus binding sequence.

The luxS gene is involved in cell–cell signalling for toxin production in Clostridium perfringens

“…It is well known that toxin genes such as pfoA, colA and plc are co-ordinately regulated by the two-component VirR/VirS system in C. perfringens (Lyristis et al, 1994;Shimizu et al, 1994;Ba-Thein et al, 1996). The response regulator protein VirR has been reported to bind directly to repeated DNA sequences located upstream of the pfoA promoter and to regulate the transcription of the pfoA gene (Cheung and Rood, 2000).…”

“…Northern hybridization was also carried out as described previously (Kobayashi et al, 1995;Ba-Thein et al, 1996), with the following exceptions. DNA fragments for gene probes were labelled with an AlkPhos-direct kit (Amersham Pharmacia Biotech), and signals were detected by CDPstar chemiluminescence.…”

The Spatial Organization of the VirR Boxes Is Critical for VirR-Mediated Expression of the Perfringolysin O Gene, pfoA , from Clostridium perfringens

“…Phosphorylated VirS then acts as a phosphate donor for the phosphorylation of the conserved Asp-57 residue of VirR. Once activated, VirR then modulates the transcription of its target genes either directly or by altering the transcription of other regulatory genes, in particular by the action of VR-RNA (6,7,18,41).…”

Gene Regulation, Two Component Regulatory Systems, and Adaptive Responses in Treponema Denticola

“…Although LytTR domains are widespread among human and plant bacterial pathogens, they are present in only a small subset of RRs (typically 1 or 2 per bacterial genome) (Galperin 2008). LytTR RRs contribute to the regulation of diverse processes and activities, including biofilm formation (Lizewski et al 2004), toxin production (Ba-Thein et al 1996;Lyristis et al 1994), type IV pili synthesis (Belete et al 2008), antimicrobial peptide production (Risoen et al 1998), flagellar assembly, flagellar function (Martin et al 2013), natural competence (Streptococcus pneumoniae) (de Saizieu et al 2000), extracellular polysaccharide biosynthesis (Pseudomonas aeruginosa) (Lizewski et al 2004;Morici et al 2007), overall fitness and virulence gene expression (Abdelnour et al 1993;Martin et al 2013). It is noteworthy that among the Spirochaetaceae, only T. denticola, T. bryantii (identifier WP_022932649) and Sphaerochaeta globosa (WP_013608153) encode LytTR domain-containing proteins (Frederick et al 2008.…”