Biofilm formation in Mesorhizobium loti. Alicia Supanitisky

SUPANITSKY, A.; ZORREGUIETA, A; LEPEK, V

Villa Carlos Paz

Congreso; VI Congreso Argentino de Microbiología General. Sociedad Argentina de Microbiología General; 2009

SAMIGE

Mesorhizobium loti interacts with Lotus spp. tissue surfaces during symbiosis relationships. Some previous studies show that biofilm formation plays a role in the interaction between bacteria and its host plant.On the other hand, the biofilm may enhance bacterial survival in soil in the absence of a legume host. Bacterial surface polysaccharides are very important in the establishing of symbiosis and attachment to surfaces. We studied biofilm formation in M. loti strain MAFF303099 and M. loti strain Ayac 1 BII by microtiter polyestirene-plate assay and CV-stained, under various conditions. We found that biofilm formation was greater when the bacteria were grown in minimal media rather than in rich media (TY) in cultures shaken. Strain MAFF shows maximal biofilm formation when the bacteria were grown in minimal media Y manitol 0.2%, for 4 days to an initial optical density at 595 nm of 0.001 while strain Ayac 1 BII shows the optimal attachement in minimal media AB sacarosa 0.5 %, when were grown for 3 days to an initial optical density at 595 nm of 0.1. Our results show that biofilm formation in M. loti differs from one bacterial strain to another under diferent cultures conditions.   Previously we had null mutants in M. loti Ayac 1 BII affected in the synthesis of lipopolysaccharide (LPS), b(1-2) cyclic glucan and the gene codes for the phosphoglucomutase (pgm). M. loti lps B2 mutant strain produces LPS with reduced amount of O-antigen and M.loti B1 mutant produces LPS totally devoid of O-antigen, M. loti pgm mutant contains an altered form of LPS, lacks EPS and cyclic glucan. These null mutants were evaluated in the optimal condition to biofilm formation to M. loti Ayac 1 BII. Only M. loti pgm mutant was unable to grow in biofilm suggesting that EPS is crucial for biofilm formation in Mesorhizobium loti Ayac 1 BII. Based on the genome sequence of M. loti strain MAFF303099 we are construing null mutants in EPS to complete this study.