Influence of secreted proteins by Rhizobium leguminosarum bv. viciae in cell-to-cell interactions

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

Villa Carlos Paz, Córdoba, Argentina

Congreso; XXXVII Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB).; 2001

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

INFLUENCE OF SECRETED PROTEINS BY RHIZOBIUM LEGUMINOSARUM BVVICIAE IN CELL-TO-CELL INTERACTIONS. Russo Daniela M., Dankert Marcelo, Downie J. Allan, Zorreguieta Angeles. Instituto de Investigaciones Bioquímicas Fundación Campomar, Buenos Aires. e-mail: drusso@leloir.org.ar Several secreted molecules produced by Rhizobium are involved in signalling between plant and bacterium. So far, few extracelullar proteins secreted by Rhizobium were characterised. The type I protein secretion system of Rhizobium leguminosarum bv viciae encoded by prsDE is responsible for secreting two beta 1,4 glycanases PlyA and PlyB, the nodulation factor NodO, and seven unidentified extracelullar proteins. The glycanases are able to cleave the EPS only when they are in contact with the cell surface.  Macroscopic observations indicated that the secretion mutants are altered in biofilm formation. To visualise early events of biofilm formation in vivo by using confocal scanning laser microscopy we labelled the cells with a GFP-expressing plasmid.  Initial steps of biofilm formation, i.e., cell-surface and cell to cell interactions were studied in the wild type Rhizobium and in different mutant derivatives that are defective in the secretion system (prsD and prsE), glycanases production (plyA, plyB, plyAplyB) and EPS production (pssA). Attachment to the glass surface, cell to cell interaction and microcolonies establishment were reduced in the secretion mutants, suggesting that the defective secretion phenotype alters the initial steps of biofilm formation. These observations lead us to propose that the secreted proteins by the PrsDE system are required for both the initiation and the development of the biofilm during free living bacteria.