title: The eukaryotic-type serine/threonine protein kinase Stk is required for biofilm formation and virulence in Staphylococcus epidermidis.
abstract: BACKGROUND
  Serine/threonine kinases are involved in gene regulation and signal transduction in prokaryotes and eukaryotes. Here, we investigated the role of the serine/threonine kinase Stk in the opportunistic pathogen Staphylococcus epidermidis.
  
  
  RESULTS
  We constructed an isogenic stk mutant of a biofilm-forming clinical S. epidermidis isolate. Presence of stk was important for biofilm formation in vitro and virulence in a murine subcutaneous foreign body infection model. Furthermore, the stk mutant exhibited phenotypes indicating an impact of stk on metabolic pathways. Using different constructs for the genetic complementation of the stk mutant strain with full-length Stk or specific Stk domains, we determined that the Stk intracellular kinase domain is important for biofilm formation and regulation of purine metabolism. Site-specific inactivation of the Stk kinase domain led to defective biofilm formation, in further support of the notion that the kinase activity of Stk regulates biofilm formation of S. epidermidis. According to immunological detection of the biofilm exopolysaccharide PIA and real-time PCR of the PIA biosynthesis genes, the impact of stk on biofilm formation is mediated, at least in part, by a strong influence on PIA expression.
  
  
  CONCLUSIONS
  Our study identifies Stk as an important regulator of biofilm formation and virulence of S. epidermidis, with additional involvement in purine metabolism and the bacterial stress response.
authors.affiliation: Key Laboratory of Medical Molecular Virology, Institutes of Biomedical Sciences, Fudan University, Shanghai, People's Republic of China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Liu
authors.forename: Jiajia
authors.initials: J
authors.lastname: Fan
authors.forename: Chen
authors.initials: C
authors.lastname: Niu
authors.forename: Decheng
authors.initials: D
authors.lastname: Wang
authors.forename: Jianping
authors.initials: J
authors.lastname: Wang
authors.forename: Xing
authors.initials: X
authors.lastname: Wang
authors.forename: Amer E
authors.initials: AE
authors.lastname: Villaruz
authors.forename: Min
authors.initials: M
authors.lastname: Li
authors.forename: Michael
authors.initials: M
authors.lastname: Otto
authors.forename: Qian
authors.initials: Q
authors.lastname: Gao
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D018441:Biofilms / Q000254:growth & development*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics / Q000502:physiology; D015151:Immunoblotting; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D016297:Mutagenesis, Site-Directed; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D013203:Staphylococcal Infections / Q000201:enzymology / Q000235:genetics; D013212:Staphylococcus epidermidis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development* / Q000472:pathogenicity*; D014774:Virulence / Q000235:genetics / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D017346:Protein Serine-Threonine Kinases