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

ALTHABEGOITI, MARIA JULIA; COVELLI, JULIETA; PEREZ-GIMENEZ, JULIETA; QUELAS, JUAN IGNACIO; MONGIARDINI, ELIAS JAVIER; LOPEZ, MARIA FLORENCIA; LOPEZ-GARCIA, SILVINA; LODEIRO, ANIBAL

FEMS MICROBIOLOGY LETTERS

WILEY-BLACKWELL PUBLISHING, INC

Año: 2011

0378-1097

Bradyrhizobium japonicum has two types of flagella. One has thin filaments composed by the 33-kDa flagellins FliCI and FliCII (FliCI-II), and the other has thick filaments composed by the 65-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. ΔfliCI-II mutants were the more competitive, occupying 64–80% of the nodules, while ΔfliC1-4 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.