In Azospirillum brasilense, mutations in flmA or flmB genes affect polar flagellum assembly, surface polysaccharides, and attachment to maize roots

ROSSI, F.; MEDEOT, D.; LIAUDAT, J. P.; PISTORIO, M.; JOFRE, E.

MICROBIOLOGICAL RESEARCH

ELSEVIER GMBH

Año: 2016 vol. 190 p. 55 - 62

0944-5013

Azospirillum brasilense is a soil bacterium capable of promoting plant growth. Several surface componentswere previously reported to be involved in the attachment of A. brasilense to root plants. Among thesecomponents are the exopolysaccharide (EPS), lipopolysaccharide (LPS) and the polar flagellum. Flagellinfrom polar flagellum is glycosylated and it was suggested that genes involved in such a posttranslationalmodification are the same ones involved in the biosynthesis of sugars present in the O-antigen of the LPS.In this work, we report on the characterization of two homologs present in A. brasilense Cd, to the wellcharacterized flagellin modification genes, flmA and flmB, from Aeromonas caviae. We show that mutationsin either flmA or flmB genes of A. brasilense resulted in non-motile cells due to alterations in the polarflagellum assembly. Moreover, these mutations also affected the capability of A. brasilense cells to adsorbto maize roots and to produce LPS and EPS. By generating a mutant containing the polar flagellum affectedin their rotation, we show the importance of the bacterial motility for the early colonization of maizeroots.