aureus eFT508 supplier strain NCTC 8325-4 reported by Brunskill et al.[10]. Recently, they found that in the strain UAMS-1, lytS knock-out did not result in spontaneous and Triton X-100-induced lysis increasing [11]. The variation in susceptibility to Triton SC79 in vitro X-100-induced lysis between different staphylococcus strains could be explained partly by the fact that they represent different genetic background. Since that lytS mutation in S. aureus has pleiotropic effects on different murein hydrolase activity [20], we hypothesized that in S. epidermidis, lytSR regulates murein hydrolase activity in a similar manner. Zymographic analysis revealed no significant differences between 1457ΔlytSR and the parent strain

in the activities or expression of murein hydrolase isolated from both extracellular and cell wall fraction. However, quantification of the extracellular murein hydrolase activity produced by these strains demonstrated that 1457ΔlytSR produced diminished overall activity compared to that of the parental strain. As expected, microarray analysis

revealed that lrgAB opreon was downregulated in 1457ΔlytSR. In S. aureus, LrgAB has a negative regulatory effect on extracellular murein hydrolase activity and disruption of lrgAB led to a significant increase in the activity [10, 12]. cidAB operon, which encodes the holin-like counterpart of the lrgAB operon, and alsSD operon, which encodes proteins check details involved in acetoin production, were then identified. Mutation of either cidAB or alsSD operon in the S. aureus strain UAMS-1 caused a dramatic decrease in extracellular murein hydrolase activity [26, 27]. We, therefore, speculate that in S. epidermidis some other LytSR regulated proteins similar to CidAB and/or AlsSD, may exist and overcome negative effect imposed by LrgAB on extracellular murein hydrolase activity, which warrants further investigation. The role of cell death and lysis in bacterial GPCR & G Protein inhibitor adaptive

responses to circumstances has been well elucidated in a number of bacteria, such as S. aureus and P. aeruginosa. Webb et al. proposed that in P. aeruginosa cell death benefited a subpopulation of surviving cells and therefore facilitated subsequent biofilm differentiation and dispersal [28–30]. Moreover, genomic DNA released following bacterial lysis constitutes the skeleton of biofilm. Since LytSR positively regulates the activity of extracellular murein hydrolases, it may affect cell viability and function in biofilm formation. By using the CLSM, significant decrease in red fluorescence was observed inside biofilm of 1457ΔlytSR, which indicated reduced loss of cell viability. Quantitative analysis showed that the percentage of dead cells inside biofilm of the wild type strain was approximately two times higher than that in the mutant. The results are consistent with the observation that 1457ΔlytSR displayed a reduction in activity of extracellular murein hydrolases. Disruption of either cidA or alsSD genes on the S.