Methods: S. gordonii mutants for both SGO_1180 and SGO_1181 were generated. These strains, wild-type S. gordonii DL1, and other previously characterized adhesin mutant strains were analyzed in a 96-well plate biofilm formation assay. Mutant strains were inoculated into antibiotic-supplemented THB and grown for 24 hrs. Wild-type cells were treated identically except no antibiotic was added. Biofilm formation in each well was quantified spectrophotometrically using crystal violet stain.
Results: When compared to wild-type, S. gordonii SGO_1180 and SGO_1181 mutants showed increased biofilm formation, which was similar to the biofilm phenotypes of previously characterized SrtA and SspAB mutants.
Conclusions: SGO_1180 and SGO_1181 gain-of-function mutants appear to represent novel sensor and response regulator components, respectively, of a two-component system (TCS) involved in regulating biofilm formation. Previous studies suggest that this TCS responds to the C-pep cleaved from SspA by SrtA. Future studies will characterize the interactions between C-pep and SGO_1180 and SGO_1181 mutants to understand how this novel TCS affects expression of other S. gordonii LPXTG-motif adhesin proteins.
Keywords: Adhesion, Biofilm and Oral biology