Role of lpsB in Sinorhizobium meliloti biofilm formation

SORROCHE FG, RUSSO DM, NIEVAS FL, RINAUDI LV, ZORREGUIETA A, GIORDANO WF

Villa Carlos Paz, Córdoba

Congreso; XLIV Reunión Anual de la SAIB; 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 that is involved in LPS (lipopolysaccharide) core biosynthesis, mutation of this 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 both 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 contrast, a stronger alteration was observed in Rm8530 lpsB, as compared to Rm8530. 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.