Constitutive expression of PcsB suppresses the requirement for the essential VicR (YycF) response regulator in Streptococcus pneumoniae R6^§

Abstract

SummaryWe report several new findings about the function of the essential VicRK two-component regulatory system (TCS) in the human pathogen Streptococcus pneumoniae . The vicR -encoded response regulator, vicK -encoded histidine kinase and the protein encoded by the downstream vicX gene are the homologues of the YycF, YycG and YycJ proteins, respectively, studied previously in Bacillus subtilis and Staphylococcus aureus. Using a regulatable promoter, we demonstrated that the VicK histidine kinase is conditionally required for growth of S. pneumoniae . Likewise, we found that the VicX protein is also conditionally required for growth and probably plays a role in the essential signal transduction pathway mediated by VicR and VicK. Recovery of limited substitutions in the conserved aspartate 52 residue (D52) of VicR was consistent with a requirement for phosphorylation of VicR for growth under some conditions. We applied microarrays to characterize the changes in transcription patterns in bacteria depleted for vicRKX operon expression. Our results suggest that the pcsB gene is a target of the VicRK TCS. We present evidence that downregulation of pcsB could account for many of the defects in cell growth, shape, size and morphology observed in bacteria depleted for vicRKX expression. Furthermore, constitutive expression of pcsB + + + + suppressed the essential requirement for the VicRK TCS and allowed the isolation of vicR null mutants.

Two-component signal transduction systems in oral bacteria

“…Table 2 shows comparisons of VicR gene targets among streptococcal species of the oral cavity and oropharynx. PcsB/GbpB are cell-surface murein hydrolases with CHAP amidase domains and are part of the divisome, at least in S. pneumoniae [119–122]. PcsB/GbpB was implicated in the essentiality of VicRK in S. pneumoniae , where vicR deletion is possible only when pcsB is induced [119].…”

“…PcsB/GbpB are cell-surface murein hydrolases with CHAP amidase domains and are part of the divisome, at least in S. pneumoniae [119–122]. PcsB/GbpB was implicated in the essentiality of VicRK in S. pneumoniae , where vicR deletion is possible only when pcsB is induced [119]. In S. mutans , GbpB/PcsB is required for surface binding to glucan exopolysaccharides synthesized from sucrose during biofilm formation [111].…”

Regulation of bacterial virulence gene expression by cell envelope stress responses

“…Microarray studies revealed that VicKR/ WalKR affected the expression of several S. pneumoniae virulence genes. [190][191][192] These include genes encoding the PiaBCDA ABC transporter involved in iron uptake; Pneumococcal Surface Protein A, which is one of the most studied S. pneumoniae virulence factors and is involved in complement evasion (PspA, not to be confused with the unrelated phage shock protein A); and some other surface proteins linked to virulence. However, when different growth conditions and genetic manipulations were compared, only a subset of genes showed strong dependence on VicKR/ WalKR in all cases.…”

Defects in ex vivo and in vivo growth and sensitivity to osmotic stress of group A Streptococcus caused by interruption of response regulator gene vicR

“…FasBCA is involved in the regulation of several growth-phase-associated virulence factors (Kreikemeyer SPy0528/SPy0529 is homologous to YycFG or VicRK (referred as VicRK in this report). VicR is essential in Bacillus subtilis (Fabret & Hoch, 1998), Staphylococcus aureus (Martin et al, 1999) and Streptococcus pneumoniae (Lange et al, 1999;Throup et al, 2000), and vicR cannot be inactivated unless VicR is provided in trans to these organisms (Throup et al, 2000) or PcsB is constitutively expressed in S. pneumoniae (Ng et al, 2003). VicK is also essential in B. subtilis, but not in S. pneumoniae and Streptococcus mutans (Fabret & Hoch, 1998;Echenique & Trombe, 2001;Senadheera et al, 2005).…”

“…VicK is also essential in B. subtilis, but not in S. pneumoniae and Streptococcus mutans (Fabret & Hoch, 1998;Echenique & Trombe, 2001;Senadheera et al, 2005). Since an unconditional vicR mutant is not available, various strategies, including bioinformatics, construction of hybrid regulator, depletion and overexpression of VicRK, and vicK inactivation, have been used to identify putative targets of VicRK (Fukuchi et al, 2000;Howell et al, 2003;Ng et al, 2003;Durac & Msadek, 2004;Mohedano et al, 2005;Senadheera et al, 2005). Nevertheless, the essential processes regulated by VicRK in these organisms remain unknown.…”