A member of the Rhodobacteraceae promotes initial biofilm formation via the secretion of extracellular factor(s)

Abstract

The Rhodobacteraceae are a relatively dominant bacterial family found in marine biofilms that can rapidly colonize natural and engineered surfaces. However, the role of this group in the development of biofilms is yet to be resolved. This study investigated the contribution of a representative isolate of the Rhodobacteraceae in the formation of initial multi-isolate biofilms. Six different bacterial strains, including Rhodo35, the member of the Rhodobacteraceae, were isolated from a marine biofilm. These isolates were used as a laboratory model system for studying a biofilm-forming marine community. A significantly higher initial biofilm biomass was observed in the presence of Rhodo35, as revealed by crystal violet staining assay, confocal laser scanning microscopy and quantitative real-time PCR. Moreover, we show that the promotion of the biofilm initiation was mediated by extracellular factor(s) secreted by Rhodo35, which increased the biomass of the biofilms by approx. 50%. In addition, Rhodo35 also increased biofilm formation by a natural marine community by 26%, as measured using crystal violet staining. These findings suggest that Rhodobacteraceae may be an important group in marine biofilms, facilitating initial colonization and biofilm formation of other bacterial species through indirect contact.