Effect of environmental factors on biofilm formation in Sinorhizobium meliloti

RINAUDI, L.; RIVELLI ANTONELLI, J.; BOGINO, P.; BANCHIO, E.; ZORREGUIETA, A.; GIORDANO, W.

Villa Giardino, Córdoba

Congreso; XV Reunión Científica Anual de la Sociedad de Biología de Córdoba; 2005

Sociedad de Biología de Córdoba

Rhizobia are soil bacteria able to fix nitrogen in symbiosis with legumes. In natural environments, bacteria are often found as sessile communities known as biofilms. To characterize the Rhizobia biofilm, an in vitro model was adapted where S. meliloti develops a biofilm on the abiotic surface of a microtiter dish wells. Biofilm was detected by staining with crystal violet and quantified by OD measurement at 560 nm. S. meliloti was able to form a biofilm on the abiotic surface in different media. However biofilm formation was higher in minimal medium (Rhizobium Defined Medium; RDM) compared with rich medium (Luria-Bertain; LB and Tryptone-Yeast extract; TY). This observation indicates that sessile growth may represent a survival strategy in a nutritionally limited environment. The presence of increasing concentrations of sucrose as carbon source in RDM, increased biofilm formation. However, this effect is not related with osmolarity produced by sucrose, since bacterial adherence was decreased at high osmolarity in the presence of the osmolyte NaCl. In a 5.0-9.5 pH range, the optimal production of biofilm was obtained at pH 7.0. Therefore, these observations indicate that environmental and nutritional conditions influence S. meliloti biofilm formation.