SarA positively controls bap-dependent biofilm formation in Staphylococcus aureus.
The biofilm-associated protein Bap is a staphylococcal surface protein involved in biofilm formation. We investigated the influence of the global regulatory locus sarA on bap expression and Bap-dependent biofilm formation in three unrelated Staphylococcus aureus strains. The results showed that Bap-dependent biofilm formation was diminished in the sarA mutants by an agr-independent mechanism. Complementation studies using a sarA clone confirmed that the defect in biofilm formation was due to the sarA mutation. As expected, the diminished capacity to form biofilms in the sarA mutants correlated with the decreased presence of Bap in the bacterial surface. Using transcriptional fusion and Northern analysis data, we demonstrated that the sarA gene product acts as an activator of bap expression. Finally, the bap promoter was characterized and the transcriptional start point was mapped by the rapid amplification of cDNA ends technique. As expected, we showed that purified SarA protein binds specifically to the bap promoter, as determined by gel shift and DNase I footprinting assays. Based on the previous studies of others as well as our work demonstrating the role for SarA in icaADBC and bap expression, we propose that SarA is an essential regulator controlling biofilm formation in S. aureus.
Trotonda
María Pilar
MP
Instituto Valenciano de Investigaciones Agrarias, Carretera Náquera-Moncada Km 4,5, 46113 Moncada, Valencia, Spain.
Manna
Adhar C
AC
Cheung
Ambrose L
AL
Lasa
Iñigo
I
Penadés
José R
JR
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D018441:Biofilms; D018983:DNA Footprinting; D003850:Deoxyribonuclease I; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000502:physiology; D011485:Protein Binding / Q000235:genetics; D013211:Staphylococcus aureus / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D024363:Transcription Initiation Site / Q000502:physiology; D014158:Transcription, Genetic / Q000502:physiology
C095698:Agr protein, Staphylococcus aureus; D001426:Bacterial Proteins; C425726:Bap protein, Staphylococcus aureus; C492107:SarA protein, Staphylococcus aureus; D015534:Trans-Activators; D003850:Deoxyribonuclease I