INVESTIGADORES
VOJNOV Adrian Alberto
congresos y reuniones científicas
Título:
Influencia del Quorum sensing en el desarrollo de biofilm en Xanthomonas campestris pv. campestris
Autor/es:
MALAMUD F; TORRES P; RIGANO L; VOJNOV A
Lugar:
Universidad de Quilmes, Quilmes, Buenos Aires
Reunión:
Congreso; III Reunión Anual de la Sociedad Argentina de Microbiología General (SAMIGE); 2006
Resumen:
The synthesis of extracellular enzymes and extracellular polysaccharide (EPS) in black rot-causing Xanthomonas campestris pv campestris (Xcc) is regulated by a cluster of nine genes, rpfA-I (for regulation of pathogenicity factors). Several of these genes are involved in regulation mediated by small diffusible signal factor (DSF). Previous reports showed that mutation (through transposon insertion) of either rpfF or rpfB haltered production of DSF, while mutation of rpfC leads to an overproduction in DSF. In addition, the mutants grew as matrix-enclosed aggregates in L medium, whereas the wild type grew in a dispersed planktonic way. Here we show, in minimal medium, a new three-dimensional biofilm structure formed by wild type strain but not by the mutants. The studies were made (purchased) using a confocal laser scanning microscopy (CLSM) analysis of GFP-labelled bacteria. The Xcc growth and microcolonies development into a characteristic biofilm  was observed. An EPS defective mutant also did not show a biofilm formation. Extracellular complementation studies of mixed bacterial cultures confirmed the essential role of the DSF modulating biofilm structure. Mixed cultures of EPS and rpfF mutants formed typical biofilms incorporating both types of bacteria. In Planta, wild-type Xcc strain 8004 was previously shown to induce necrotrophic symptoms on Nicotiana benthamiana (Nb) leaves. To investigate DSF-mediated regulation during plant-pathogen interaction, mutants derived from 8004 were subjected to leaf-infiltration assays. It was founded that EPS-deficient mutant 8397, DSF-deficient rpfF 8523 and DSF-hyper producing rpfC 8557 were all severely compromised in their ability to cause disease in Nb leaves compared with the wild-type. Co-infiltration assays showed that the 8397 but not 8557 was able to complement 8523. In addition, 8557 interfered with 8004 pathogenicity when both were co-inoculated in Nb leaves. All together, suggest a role of DSF in biofilm formation and the importance of those structures in pathogenicity.