Analysis of the Role of the Two Flagella of Bradyrhizobium japonicum in Competition for Nodulation of Soybean

ALTHABEGOITI, M.J; COVELLI, J.M; PÉREZ-GIMÉNEZ, J; QUELAS, J. I; MONGIARDINI, E. J; LÓPEZ, M. F; LÓPEZ-GARCÍA, S. L; LODEIRO A.R

FEMS MICROBIOLOGY LETTERS

WILEY-BLACKWELL PUBLISHING, INC

Año: 2011 vol. 319 p. 133 - 139

0378-1097

Bradyrhizobium japonicum has two types of flagella. One has thin filamentsconsisting of the 33-kDa flagellins FliCI and FliCII (FliCI-II) and the other hasthick filaments consisting of 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 backgroundsof two derivatives from the reference strain USDA 110: the streptomycin-resistantderivative LP 3004 and its more motile derivative LP 3008. All mutationsdiminished swimming motility. When each mutant was co-inoculated with theparental strain on soybean plants cultivated in vermiculite either at field capacityor flooded, their competitiveness differed according to the flagellin altered. DfliCIIImutants were more competitive, occupying 64?80% of the nodules, whileDfliC1-4 mutants occupied 45?49% of the nodules. Occupation by the nonmotiledouble mutant decreased from 55% to 11% as the water content of the vermiculiteincreased from 85% to 95% field capacity to flooding. These results indicate thatthe influence of motility on competitiveness depended on the water status of therooting substrate.