Identification of a Novel Essential Two-Component Signal Transduction System, YhcSR, inStaphylococcus aureus

Abstract

Two-component signal transduction systems play an important role in the ability of bacteria to adapt to various environments by sensing changes in their habitat and by altering gene expression. In this study, we report a novel two-component system, YhcSR, in Staphylococcus aureus which is required for bacterial growth in vitro. We found that the down-regulation of yhcSR expression by induced yhcS antisense RNA can inhibit and terminate bacterial growth. Moreover, without complementary yhcS or yhcR, no viable yhcS or yhcR gene replacement mutant was recoverable. Collectively, these results demonstrated that the YhcSR regulatory system is indispensable for S. aureus growth in culture. Moreover, induced yhcS antisense RNA selectively increased bacterial susceptibility to phosphomycin. These data suggest that YhcSR probably modulates the expression of genes critical for bacterial survival and may be a potential target for the development of novel antibacterial agents.Staphylococcus aureus is an important community-and hospital-acquired pathogen that causes superficial skin and lifethreatening infections worldwide (25,33). The pathogenesis of S. aureus is partially due to the coordinated regulation of virulence factors allowing the bacterium to evade the host immune system and/or to promote survival during infection. This organism has developed a series of two-component signal transduction systems (TCSs) in order to sense its immediate surroundings and to modulate specific cellular responses and the expression of virulence genes (14, 32). Therefore, TCSs are being explored as potential targets for new antimicrobials (2,17,28).A typical TCS is composed of a membrane-associated histidine kinase, which acts as a sensor protein extending through the cytoplasmic membrane to monitor environmental changes and to activate a response regulator existing in the cytoplasm modulating gene expression (15,34). The well-studied TCS Agr is a positive regulator of exoproteins, including proteases, hemolysins, and toxins (32). Additionally, the TCS Agr is a repressor of the transcription of protein A, coagulase, and some adhesins in late-exponential-phase growth in vitro (32). Other two-component systems, such as saeRS, arlRS, and srrAB, also influence the expression of some virulence factors (1,13,11,35,39). Another system, LytSR, controls bacterial autolysis by positively regulating the transcription of genes responsible for the synthesis and transport of cell wall murein hydrolase (4). The vraSR loci are homologous to the yvqEC loci of B. subtilis and positively modulate cell wall biosynthesis in S. aureus (23).The yycFG system, which has orthologs in Bacillus subtilis (7,8) and Streptococcus pneumoniae (36), is the only known regulatory system essential for cell viability in S. aureus (26). It was reported that in B. subtilis the YycFG system controls the ftsAZ operon, which is involved in the process of cell wall division (12). However, there is no such evidence in S. aureus and S. pneumoniae, while it has been reported that YycF ...

NsaRS is a cell-envelope-stress-sensing two-component system of Staphylococcus aureus

“…Furthermore, microarray analysis in this study reveals that NsaRS is responsible for regulation of another TCS, yhcSR. Previous studies with cells depleted for yhcSR reveal elevated sensitivity to this antibiotic (Sun et al, 2005), suggesting interplay between these two systems when sensing phosphomycin-mediated damage. Further to this, using a plate-based screening assay, we demonstrate that ampicillin and penicillin G, both of which are involved in extracellular peptidoglycan cross-linking, results in increased nsaRS expression.…”

The Essential Two-Component System YhcSR Is Involved in Regulation of the Nitrate Respiratory Pathway of Staphylococcus aureus

“…Bioinformatic analysis of the YhcR amino acid sequence revealed that YhcR has more than 30% identity with the NarL protein, suggesting that the YhcSR system may belong to the NarL family and be associated with regulation of the nitrate respiratory pathway in S. aureus (data not shown). A TetR-regulated antisense RNA technology has been successfully used to investigate gene function in S. aureus (10,29). Our previous studies have demonstrated that induced yhcS antisense RNA can effectively downregulate endogenous yhcR expression (29).…”

“…A TetR-regulated antisense RNA technology has been successfully used to investigate gene function in S. aureus (10,29). Our previous studies have demonstrated that induced yhcS antisense RNA can effectively downregulate endogenous yhcR expression (29). In order to test whether YhcSR is involved in regulation of the nitrate respiratory pathway, we utilized the same TetR-regulated yhcS antisense RNA expression system and examined the impact of downregulating yhcSR expression on growth in the presence or absence of nitrate under anaerobic conditions.…”

“…In order to differentiate which identified genes are directly regulated by the yhcSR regulator, we purified His-tagged YhcS and YhcR proteins, as described previously (29). Both yhcS and yhcR coding regions were obtained by PCR from S. aureus using corresponding primers (Table 1) and cloned into NdeI and XhoI sites of the E. coli expression vector pET24b.…”

“…Two-component signal (TCS) transduction systems play important roles in the adaptation of the microbial organisms within different niches, as well as in pathogenesis and biofilm formation for various bacterial species (7,15,22,27). Our previous studies have demonstrated that a novel two-component signal transduction system, YhcSR, is required for the viability of S. aureus in vitro culture (29). However, the biological function of YhcSR is still unclear.…”