The Impact of Bifidobacterium bifidum and its Surface Protein BopA on the Murine Intestinal Barrier and Endogenous Microbiota Composition

Bifidobacterium bifidum MIMBb75 is a novel strain whose behavior within the intestinal tract is not known. This work attempts to determine the survival and molecular determinant responsible for its colonization through two studies involving administration to mice of 1) B. bifidum MIMBb75 or 2) engineered B. longum NCC2705 expressing the B. bifidum-specific surface protein BopA. MIMBb75 was able to transiently colonize the murine intestinal tract. As a result, endogenous bifidobacteria increased significantly in the proximal colon whereas Clostridia clusters were differentially affected in a region-dependent fashion. Genetically engineered B. longum NCC2705, expressing the BopA gene, did not impact endogenous bacterial groups in the proximal colon or feces, albeit, it down-regulated the gene expression of KC and mucin 4 in the proximal colon. These outcomes indicate that MIMBb75 encompasses characteristics of a probiotic, but further studies are required to assess the role of BopA as the molecular determinant of its action.