Analysis of the role of the two flagella of Bradyrhizobium japonicum in competition for nodulation of soybean

ALTHABEGOITI, MJ; COVELLI, J; PEREZ GIMENEZ, J; QUELAS, JI; MONGIARDINI, EJ; LOPEZ, MF; LOPEZ GARCIA, SL; LODEIRO, AR

FEMS MICROBIOLOGY LETTERS

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Berkshire; Año: 2011

0378-1097

21 Abstract Bradyrhizobium japonicum has two types of flagella. One has thin filaments composed by the kDa flagellins FliCI and FliCII (FliCI-II), and the other has thick filaments composed by the kDa flagellins FliC1, FliC2, FliC3, and FliC4 (FliC1-4). To investigate the roles of each flagellum in competition for nodulation, we obtained mutants deleted in fliCI-II and/or fliC1-4 in the genomic backgrounds of two derivatives from the reference strain USDA 110: the streptomycin-resistant derivative LP 3004 and its more-motile derivative LP 3008. All mutations diminished swimming motility. When each mutant was co-inoculated with the parental strain on soybean plants cultivated in vermiculite either at field capacity or flooded, their competitiveness differed according to the flagellin altered. ∆fliCI-II mutants were the more competitive, occupying 64?80 % of the nodules, while ∆fliC1-4 mutants occupied 45?49 % of the nodules. Occupation by the non-motile double mutant decreased from 55 to 11 % as the water content of the vermiculite increased from 85?95 % field capacity to flooding. These results indicate that the influence of motility on competitiveness depended on the water status of the rooting substrate.