​nih.​gov/​geo/​), accession number GPL13532 for the platform design and GSE29309 for the original dataset. b P-values of RT-qPCR results were caculated using Student’s t-test. c UD: under detection level in microarray analysis or by RT-qPCR. Discussion As Staphylococci biofilm formation is influenced by external factors such as glucose, NaCl, temperature,

aerobiosis-anaerobiosis, static-dynamic conditions, and pH [36–39], it suggests Y-27632 mw that there are mechanisms that can sense environmental signals and regulate bacterial biofilm formation. In S. epidermidis, the agrC/A TCS has been proven to negatively regulate biofilm formation [15, 16], while the lytS/R TCS has been shown to positively regulate bacterial autolysis [40]. In S. aureus, the saeRS TCS influences biofilm formation [17] and the expression of virulence-ML323 associated factors [18], whereas in S. epidermidis, a mutant with saeR deletion showed a slightly higher biofilm-forming ability compared to the parental strain [11]. In the present study, SE1457ΔsaeRS, a saeR and saeS deletion mutant from S. epidermidis 1457, was constructed by homologous recombination. Although saeRS in S. epidermidis ATCC 35984 and S. aureus Newman are similar both at nucleotide sequence level (75% for saeR and 67% for saeS) and at the amino acid level (84% for SaeR and 70% for SaeS), both biofilm formation

and autolysis were up-regulated in SE1457ΔsaeRS, suggesting that saeRS in S. epidermidis plays Selleckchem ATM/ATR inhibitor a different role from that in S. aureus. Additionally, when examined by SEM, increased quantities of extracellular polymeric substances (EPSs) were

observed in the SE1457ΔsaeRS biofilm compared to the SE1457 and SE1457saec biofilms (Figure 2A). Aap expression and PIA synthesis are important for biofilm formation. Therefore, we examined the contribution of Aap and PIA to SE1457ΔsaeRS biofilm formation. In S. epidermidis, Aap plays an important role in biofilm formation, and biofilm-positive strains that express aap show higher biofilm forming abilities than strains that lack the Aap protein [41]. In SE1457ΔsaeRS, Aap up-regulation was detected using 2-DE and confirmed by Western blot, suggesting that Aap is a factor Dynein associated with the enhanced biofilm formation capacity of SE1457ΔsaeRS. PIA plays a major role in intercellular adhesion in S. epidermidis biofilms [42]. However, no obvious differences in either PIA production or transcription of icaA, the gene that encodes an N-acetylglucosaminyl transferase enzyme critical for PIA synthesis, were observed between SE1457ΔsaeRS and SE1457 (Table 3). These results are consistent with the findings reported for a saeR deletion mutant by Handke et al. [11]. The enhanced S. epidermidis biofilm formation may be correlated with the increased amounts of eDNA released in the biofilm matrix [19, 25, 28]. Quantitative PCR revealed that eDNA release from S. epidermidis 1457ΔsaeRS was up-regulated (Figure 6).