Characterization of MabA, a modulator ofLactobacillus rhamnosusGG adhesion and biofilm formation

The probiotic Lactobacillus rhamnosus GG, first isolated from healthy human gut microbiota, has been reported to adhere very well to components of the intestinal mucosa, thereby enabling transient colonization of the gastrointestinal tract (GIT). In a search for the genes responsible for the good adherence capacity of this strain, a genomic region encoding a protein with homology to putative adhesion proteins (LGG_01865) and its putative regulator (LGG_01866) was identified. The sequence of the L. rhamnosus GG LGG_01865 encodes a polypeptide of 2419 amino acid residues containing 26 repetitive DUF1542 domains and a C-terminal LPxTG cell wall-anchoring motif. Phenotypic analyses of a dedicated LGG_01865 knockout mutant revealed a reduced biofilm formation capacity on abiotic surfaces and decreased adhesion to intestinal epithelial cells and tissues of the murine GIT. This suggests a modulating role for LGG_01865 in L. rhamnosus GG-host interactions. Therefore, we propose a new name for LGG_01865, i.e. MabA, modulator of adhesion and biofilm. Expression analysis indicated that LGG_01866 plays a conditional role in the regulation of LGG_01865 expression, i.e. when cells are grown under conditions of sugar starvation. At the time of the experiments, M.P.V. held a PhD grant from the Interfaculty Council for Development Cooperation of the K.U. Leuven (IRO-16302). I.C. holds a PhD grant from the Institute for Science and Technology (IWT, Belgium). Additionally, this work was partially supported by the FWO-Vlaanderen through project G.0236.07 and by the Federal Office for Scientific, Technical and Cultural Affairs (Interuniversity Poles of Attraction Programme). We gratefully acknowledge K. Zhou, D. Verstraeten, K. Schrijvers and E. Dillissen for technical assistance. We thank D. De Coster for his skilled assistance with the qRT-PCR experiments. Dr I. Nagy and Prof. D. Bullens are acknowledged for useful suggestions. Prof. J. Ceuppens and Dr C. Shen are thanked for their guidance with the mouse experiments. We also thank M. Danielsen, P. Augustijns and R. Mols for kindly providing the plasmids and CaCo-2 cells used in this study.