The pathogenesis of Staphylococcus epidermidis (S. epidermidis) in persistent infections is primarily attributed to its ability to form biofilms on the surface of indwelling medical devices. The antibiotic tolerance of biofilm is partly due to the presence of persister cells, however, the mechanism of bacterial persistence is poorly understood. In Escherichia coli (E. coli), PhoU was reported as a persistence switch involved in persister formation and tolerance to multiple antibiotics and stresses. There are two phoU homologues (serp0956 and serp0316) in S. epidermidis. As a component of pst operon, serp0956 was designated phoU1. The other phoU homologue serp0316 which encoded a hypothetical protein was named phoU2. Our previous study revealed that deletion of phoU1 in SE1457 had no effects on biofilm formation capacity. In this report a preliminary study on phoU2 was conducted. The relative transcriptional level of phoU2 in logarithmic phase (6 h) was higher than that in stationary phase (12 h) by using quantitative real-time polymerase chain reaction (PCR). PhoU2 was expressed in E. coli with a prokaryotic expression recombinant plasmid and purified to immunize BALB/c mice by intraperitoneal injection of anti-PhoU2 antiserum. Western blotting was carried out using PhoU2 polyclonal antibody as primary antibody to monitor PhoU2 expression in S. epidermidis. It was shown that there was continuous expression of PhoU2 in both exponential and plateau phases. The expression of PhoU2 was also detected in several clinical isolates of S. epidermidis. These results indicate that PhoU2 is conserved in different strains of S. epidermidis and suggeste that PhoU2 may function as a homologue of PhoU in S. epidermidis. These data allowe us to further characterize the role of PhoU2 in the formation of biofilm and persisters in S. epidermidis.