Environmental regulation of mucR gene expression in Sinorhizobium meliloti.

RINAUDI, L., SORROCHE, F., ZORREGUIETA, A. Y GIORDANO, W.

Rosario, Argentina

Congreso; XLII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2006

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB)

Environmental conditions and nutritional status of the medium influence S. meliloti biofilm formation (Rinaudi et al., 2006). Adhesion of bacteria to different surfaces and between bacteria could be modulated according to environmental changes by regulation of the exopolysaccharide (EPS) synthesis. The promoter of the mucR EPS-regulatory gene was amplified and cloned upstream the lacZ reporter gene and the expression of the mucR-lacZ fusion was analysed under different media conditions. As expected, we observed that the expression of the mucR promoter was low in rich media but induced in a minimal media, which favours EPS production and biofilm formation. We found that the activity of the mucR promoter correlate with some of the conditions that stimulate biofilm formation. In fact, the presence of 0.3 M sucrose, 0.015 M NaCl  and 25 mM phosphate to the minimal medium had a positive effect on the mucR promoter activity. However,  no induction was observed in the presence of 7 mM calcium, which was previously observed that stimulate biofilm formation. Our data suggest that mucR dependent processes modulate biofilm formation, possibly through regulation of EPS production.