Coaggregating Delftia acidovorans facilitates the metabolic activity of partner bacteria in drinking water biofilms

Although bacterial coaggregation has already been identified as a key mechanism in the multispecies biofilms development in diverse environments, little is known about this highly specific type of cell-cell interaction in aquatic systems. In this study, a strain of Delftia acidovorans isolated from drinking water (DW) and previously described with coaggregation ability, was studied for its role in biofilm development. Single and dual-species biofilms, of D. acidovorans and the DW representative bacteria Citrobacter freundii and Pseudomonas putida, were grown in 96-well microtiter plates and characterized in terms of metabolic activity. In addition, to prove that D. acidovorans can facilitate the metabolic activity of other bacteria, single biofilms were formed in the presence of D. acidovorans cell-free supernatant (CFS). The metabolic activity was higher when comparing single with dual-species biofilms. Furthermore, in the presence of CFS, it was evident an increase in the metabolic activity of C. freundii and P. putida biofilms. These results suggest the production of extracellular metabolites by D. acidovorans, that possibly act as public goods. That said, the presence of coaggregating species, namely D. acidovorans, in biofilms appears to create a functional cooperative microbial community, providing a favorable metabolic opportunity for partner bacteria.