Development of a simple test to assess the biofilm formation in rhizobia.

RINAUDI, L., RIVELLI ANTONELLI, J., BOGINO, P. Y GIORDANO, W.

San Luis

Congreso; XXII Reunión anual de la Sociedad de Biología de Cuyo; 2004

Sociedad de Biología de Cuyo

Symbiotic nitrogen fixation by rhizobia-legume couple is a process of ecological and agricultural importance. The study of the establishment of rhizobia inoculated in legume roots, their colonization, and nodule occupancy requires the use of adequate techniques. The objectives in this research were to visualize and to quantify the Sinorhizobium meliloti biofilm formation on artificial substrates, where basically the biofilms were grown on microtiter-plate over short period time. The experimental methods were based on the ability of bacteria to form biofilms on polyvinylchloride or polystyrene surfaces. When the formation of the biofilm was monitored over an 18 h period, S. meliloti formed a biofilm mainly at the interface between the air and the liquid medium. The biofilm formation was not significantly different between the strains Rm1021 and Rm2011, two closely related strains of S. meliloti that are capable of forming nitrogen-fixing nodules in Medicago hosts. The biofilm was greater when the bacteria were incubated in the minimal media. In rich media, bacteria grew better but failed to attach to the surface, instead forming pellets at the bottom of the well. It appears that a nutritionally limited environment increases the transition from planktonic to a sessile mode of life and the subsequent development of the biofilm. The results indicate that microtiter-plate test can provide a convenient abiotic surface for studying rhizobia biofilm.