Genetic characterization of biofilm development in Rhizobium leguminosarum bv. viciae

RUSSO, DM; DANKERT, M.; DOWNIE, JA Y ZORREGUIETA, A.

Villa Carlos Paz, Córdoba, Argentina

Congreso; XXXVIII Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB); 2002

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

GENETIC CHARACTERIZATION OF BIOFILM DEVELOPMENT IN RHIZOBIUM LEGUMINOSARUM BV. VICIAE. Russo, Daniela M., Dankert, Marcelo, Downie, J. Allan (*), and Zorreguieta, Angeles. Fundación Instituto Leloir, Bs.As., Argentina. (*) John Innes Centre, Norwich, U.K. (drusso@leloir.org.ar) The PrsDE secretion system of Rhizobium leguminosarum bv. viciae is involved in the secretion of several proteins including adhesins and EPS-glycanases. We showed that the prsD and prsE secretion mutants are affected in the normal development of a biofilm in chambered slides. The plyB mutant, which is affected in the EPS processing, remembers the altered structure seen in the secretion mutants. A mutant severely affected in the EPS synthesis (pssA) was unable to attach to the surface and to develop an organised biofilm. Instead, pssA showed macroscopic detached bacterial aggregates. To determine the influence of additional secreted proteins in the formation of these aggregates, we generated a double mutant pssA prsE. The double mutant also showed macroscopic bacterial aggregates. However, these aggregates were easily disrupted when exposed to mechanical forces, supporting the idea of additional PrsDE secreted proteins involved in cell-cell interactions. Since appearance of these aggregates resembles fibrous structures, we studied the effect of cellulase treatment on aggregate stability. Both pssA and pssA prsE aggregates were dissolved, suggesting the contribution of cellulose fibrils in these interactions. To have a more complete picture of surface factors influencing biofilm formation, we recently analysed the phenotype of LPS mutants. Our data indicate that LPS mutants are strongly affected in biofilm formation. Thus, multiple surface and extracellular factors influence cell-cell interactions in Rhizobium.