O chain participates in cellular interactions during biofilm formation in Rhizobium leguminosarum

RUSSO DM; WILLIAMS A; POSADAS DM; VOZZA NF; ABDIÁN PL; DOWNIE JA; ZORREGUIETA A.

Villa Carlos Paz, Córdoba

Congreso; XLIV Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB).; 2008

SAIB

  Rhizobium leguminosarum bv. viciae develops a biofilm made of organized structures attached to a surface and consisting in multiple layers of interacting cells and water channels. The EPS and PrsDE secreted proteins are involved in the biofilm formation. The role of the O-chain LPS in these communities was studied in four Tn5- LPS mutants of R. l. v. in either 3841 or A34 backgrounds. Disrupted genes were related with the synthesis of core or O- components. All mutants showed O-chain deficiency by SDS-PAGE.  Crystal violet assays indicated that the O-chain defects may affect attachment to the surface but this is highly dependent on culture conditions. Confocal microscopy showed that three of these mutants (lpcA, lpsD and lpcB) form aberrant structures, in which cellular interactions are exclusively between bacterial poles. However, the lpsR mutant resembled the wild type. In this mutant, overproduction of cellulose and as a consequence cell aggregation was observed. An additional mutation in the cellulose synthase gene prevented cellular aggregation and induced aberrant interactions indicating that cellulose could mask the O deficiency. Taking together these results indicate that the O-chain LPS is crucial for cell-cell interactions and that cellulose could also contribute to them during biofilm formation in Rhizobium.