A Putative Type V Pilus Contributes to Bacteroides thetaiotaomicron Biofilm Formation Capacity.

is a prominent anaerobic member of the healthy human gut microbiota. While the majority of functional studies on addressed its impact on the immune system and the utilization of diet polysaccharides, biofilm capacity and its contribution to intestinal colonization are still poorly characterized. We tested the natural adhesion of 34 isolates and showed that although biofilm capacity is widespread among strains, this phenotype is masked or repressed in the widely used reference strain VPI 5482. Using transposon mutagenesis followed by a biofilm positive-selection procedure, we identified VPI 5482 mutants with increased biofilm capacity corresponding to an alteration in the C-terminal region of BT3147, encoded by the locus, which displays homology with Mfa-like type V pili found in many We show that BT3147 is exposed on the surface and that BT3147-dependent adhesion also requires BT3148, suggesting that BT3148 and BT3147 correspond to the anchor and stalk subunits of a new type V pilus involved in adhesion. This study therefore introduces as a model to study proteinaceous adhesins and biofilm-related phenotypes in this important intestinal symbiont. Although the gut anaerobe is a prominent member of the healthy human gut microbiota, little is known about its capacity to adhere to surfaces and form biofilms. Here, we identify that alteration of a surface-exposed protein corresponding to a type of pili found in many increases biofilm formation. This study lays the ground for establishing this bacterium as a model organism for and studies of biofilm-related phenotypes in gut anaerobes.