Mutation of tagO reveals an essential role for wall teichoic acids in Staphylococcus epidermidis biofilm development

The icaADBC-encoded polysaccharide intercellular adhesin (PIA) and wall teichoic acids (WTA) are structural components of Staphylococcus epidermidis biofilms. Deletion of tagO, which encodes the first enzymic step in WTA biosynthesis, had pleiotropic effects, including enhanced intercellular aggregation and autolytic activity, and impaired biofilm production. The biofilm-negative phenotype of the tagO mutant, named TAGO1, was associated with increased cell surface hydrophobicity, lower rates of primary attachment to polystyrene, and reduced icaADBC operon and PIA expression. Mild acid stress induced by growth in BHI glucose media reduced rates of stationary phase autolysis and enhanced aggregation by TAGO1, leading to formation of a pellicle, which unlike a biofilm was only loosely attached to the polystyrene surface. TAGO1 pellicles were dispersed by proteinase K and DNase I but not sodium metaperiodate, implicating protein and extracellular DNA (eDNA) and not PIA in this phenotype. Substantially increased levels of eDNA were recovered from TAGO1 culture supernatants compared with the wild-type. These data indicate that WTA are essential for the primary attachment and accumulation phases of the S. epidermidis biofilm phenotype. Furthermore, in the absence of WTA, proteins and eDNA can promote cell aggregation and pellicle formation, which also appear to limit interactions with artificial surfaces.