Treatment of S. epidermidis infection has become a troublesome

problem as biofilm-associated bacteria exhibit enhanced resistance to antibiotics and to components of the innate host defences [4, 5]. Among the Staphylococci, the other major human pathogen is Staphylococcus aureus, which causes infections ranging from cutaneous infections and food poisoning to life-threatening septicaemia. Aside from biofilm, S. aureus produce a large AZD7762 chemical structure array of exotoxins and exoezymes [6]. Two-component regulatory systems (TCSs) play a pivotal role in bacterial adaptation, survival, and virulence by sensing changes in the external environment and modulating gene expression in response to a variety of stimuli [7–9]. Among the TCSs identified in the genomes of S. epidermidis, functions of LytSR are unknown, though in S. aureus LytSR has been demonstrated to play a role in bacterial autolysis and biofilm formation. LytSR two-component regulatory system was firstly identified from the S. aureus genome. The lytS integration mutant of S. aureus strain NCTC 8325-4 exhibited a marked propensity

to form aggregates in liquid culture and an increased rate of penicillin-and Triton X-100-induced this website lysis. In combination with subsequent zymographic analysis, it was suggested that LytSR is involved in either regulation of murein hydrolases gene expression or modulation of murein hydrolase activity [10]. Recently, Shrama et al. reported that a lytS knockout mutant of S. aureus strain UAMS-1 produced more adherent biofilm [11]. In search of genes regulated by LytSR in S. aureus, two additional open reading frames immediately downstream from lytS and lytR were identified and designated gene lrgA and lrgB, whose transcription was positively regulated by LytSR and the global regulators Agr and SarA. It was proposed that LrgA, and possibly LrgB, Glutamate dehydrogenase functions in a similar way to an antiholin, i.e., blocking

murein hydrolases access to the substrate peptidoglycan [12]. Bayles et al. put forward the possibility that LrgAB exploits a molecular strategy, which is functionally analogous to that mediated by the eukaryotic Bcl-2 family of apoptosis regulatory proteins, to control bacterial programmed cell death [13, 14]. Recent study suggested that LytSR regulatory system sense a collapse in membrane potential and then induce the transcription of the lrgAB operon [15]. Several TCSs of S. aureus, such as agr and arlRS, have been proven to affect biofilm formation, whereas little has been known in the case of S. epidermidis. In S. aureus and S. epidermidis, an agr mutant forms a significantly thicker biofilm. However, the agr regulons of the two species comprise different genes. Autolysin E (AtlE) which has been documented to mediate Lazertinib nmr initial attachment of S. epidermidis to a polymer surface, overexpresses in an agr mutant, whereas the homologus Atl protein in S. aureus is not under agr control [16, 17].