Role of lpsB in Sinorhizobium meliloti Biofilm Formation

SORROCHE, F.G., RUSSO, D.M., NIEVAS, F.L., RINAUDI, L.V., ZORREGUIETA, A., GIORDANO W.F.

Carlos Paz, Córdoba

Congreso; XLIV Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2008

SAIB

Biofilms are populations or communities adhered to an interface and surrounded by an extracellular matrix. S. meliloti, a symbiotic Gram negative bacteria, is able to form biofilms in vitro. In this bacteria, lpsB codes for a glucosyltransferase which is involved in LPS (lipopolysaccharide) core biosynthesis: mutation of lpsB gene results in an altered LPS composition. In order to study the impact of lpsB in S. meliloti biofilm formation, we performed confocal laser scanning microscopy  and cristal violet adhesion experiments in two lpsB mutant strains. Rm6963 (Rm2011 lpsB::Tn5) showed a reduced adhesion to polypropylene and polystyrene, as compared to Rm2011 (wild type strain). In contrast, such adhesion-deficient phenotype was not observed in Rm8530 lpsB as compared to Rm8530 (Rm1021 derivative, expR+, galactoglucan producer). Cell-cell interactions and mature biofilm structures were altered in lpsB mutants: a partial inhibition of lateral interactions and characteristic arrays of bacteria with polar interactions were observed. The mature biofilm structure was slightly altered in Rm6963, as compared to Rm2011. In conclusion lpsB has a role in determining cell-cell interactions and mature biofilms structures, but adhesion to hydrophobic surfaces behaviors of lpsB mutants are strain-dependent. In contrast, a stronger alteration was observed in Rm8530 lpsB, as compared to Rm8530.