Azospirillum brasilense flmAB: its role in glycosylation, motility and attachment to maize roots.

ROSSI F; FERRARI W; MEDEOT D; RIVERO MR; CASTRO M; FISCHER S; PISTORIO M; JOFRE E

Congreso; SAIB 2012; 2012

Azospirillum brasilense is a diazotrophic motile microorganism found in the rhizosphere of cereals. The polar flagellum was shown to play a role in the adhesion of cells to plant roots. Previous studies have confirmed that the polar flagellin is glycosylated in A. brasilense, however, the genes required for such glycosylation as well as the role of this modification, have not been described yet. The aim of present study was to identify the genes of A. brasilense responsible for the glycosylation of the flagellin. In silico analysis revealed flmA and flmB genes as putative candidates. Mutations in either flmA (dehydratase) or flmB (aminotransferase) resulted in a severely impaired swimming phenotype. TEM analysis revealed the presence, in both mutants, of a truncated polar flagellum. Moreover, the attachment of these mutant strains to maize roots was significantly lower than the wild-type strain in competition assays, suggesting the participation of the polar flagellum in the establishment of the plant-bacteria interaction. Purified flagellins from the wild-type, mutants and complemented strains were separated by SDS-PAGE and then stained for the detection of sugars. Contrary to the wild-type strain, in both mutant strains no glycosylation signals were detected suggesting that the products of genes flmA and flmB are required for glycosylation of the flagellin.