The role of flagella in motility and biofilm formation in Xanthomonas axonopodis pv citri.

FLORENCIA MALAMUD; PABLO S. TORRES; RIGANO LUCIANO A; ATILIO P. CASTAGNARO; MARIA ROSA MARANO; ADRIÁN A. VOJNOV

Cancun, Mexico

Conferencia; ASM CONFERENCE ON BIOFILMS; 2009

American Society for Microbiology

Xanthomonas axonopodis pv. citri (Xac) is the causative agent of citrus canker, an important threat to the citrus industry worldwide. Previous work in our laboratory demonstrated that Xac is able to form biofilm communities in biotic and abiotic surfaces, where the extracellular polysaccharide xanthan (eps) plays a key role in the biofilm maturation. Biofilm formation in other bacteria is a flagellar-dependent process. Xac has a unique polar flagellum, to evaluate its participation in biofilm development we generated two mutants: Xac fliC (flagelin gene) and Xac flgE (hook gene), both involved in the flagellar structure. By crystal violet technique we observed that flagellar mutants were impaired in the first steps of biofilm development, but their ability to stick to the bottom of the Polystyrene-well was partially recovered after 72 h. By confocal microscopy we have observed that these mutants were able to adhere but not to form a mature structure as wild type Xac did. We show in this work that Xac has the capability to swim and to performed another type of movement that shows to be flagellar-independent, but eps and quorum sensing-dependent. All mutants affected in the flagellar-independent motility described here, exhibit a dispersal growth without any cell-cell architecture in biofilm growth conditions. We propose that this type of surface translocation was found to be important for this bacterium at the adhesion step of biofilm development. The lost of flagellum was responsible for the impossibility of the mutants to be able to develop a mature biofilm.