The Transcription Factor SpoVG Is of Major Importance for Biofilm Formation of under In Vitro Conditions, but Dispensable for In Vivo Biofilm Formation.

is a common cause of device related infections on which pathogens form biofilms (i.e., multilayered cell populations embedded in an extracellular matrix). Here, we report that the transcription factor SpoVG is essential for the capacity of to form such biofilms on artificial surfaces under in vitro conditions. Inactivation of in the polysaccharide intercellular adhesin (PIA) producing strain 1457 yielded a mutant that, unlike its parental strain, failed to produce a clear biofilm in a microtiter plate-based static biofilm assay. A decreased biofilm formation capacity was also observed when 1457 Δ cells were co-cultured with polyurethane-based peripheral venous catheter fragments under dynamic conditions, while the -complemented 1457 Δ derivative formed biofilms comparable to the levels seen with the wild-type. Transcriptional studies demonstrated that the deletion of significantly altered the expression of the intercellular adhesion () locus by upregulating the transcription of the operon repressor and down-regulating the transcription of . Electrophoretic mobility shift assays (EMSA) revealed an interaction between SpoVG and the - intergenic region, suggesting SpoVG to promote biofilm formation of by modulating expression. However, when mice were challenged with the 1457 Δ mutant in a foreign body infection model, only marginal differences in biomasses produced on the infected catheter fragments between the mutant and the parental strain were observed. These findings suggest that SpoVG is critical for the PIA-dependent biofilm formation of under in vitro conditions, but is largely dispensable for biofilm formation of this skin commensal under in vivo conditions.