title: Analysis of the role of the two flagella of Bradyrhizobium japonicum in competition for nodulation of soybean.
abstract: Bradyrhizobium japonicum has two types of flagella. One has thin filaments consisting of the 33-kDa flagellins FliCI and FliCII (FliCI-II) and the other has thick 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 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 more competitive, occupying 64-80% of the nodules, while ΔfliC1-4 mutants occupied 45-49% of the nodules. Occupation by the nonmotile double mutant decreased from 55% to 11% as the water content of the vermiculite increased from 85% to 95% field capacity to flooding. These results indicate that the influence of motility on competitiveness depended on the water status of the rooting substrate.
authors.affiliation: Departamento de Ciencias Biológicas, Instituto de Biotecnología y Biología Molecular, Facultad de Ciencias Exactas, Universidad Nacional de La Plata y CCT La Plata-CONICET, La Plata, Argentina.
authors.forename: Maria Julia
authors.initials: MJ
authors.lastname: Althabegoiti
authors.forename: Julieta M
authors.initials: JM
authors.lastname: Covelli
authors.forename: Julieta
authors.initials: J
authors.lastname: Pérez-Giménez
authors.forename: Juan Ignacio
authors.initials: JI
authors.lastname: Quelas
authors.forename: Elías J
authors.initials: EJ
authors.lastname: Mongiardini
authors.forename: Maria Florencia
authors.initials: MF
authors.lastname: López
authors.forename: Silvina L
authors.initials: SL
authors.lastname: López-García
authors.forename: Aníbal R
authors.initials: AR
authors.lastname: Lodeiro
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D020369:Bradyrhizobium / Q000235:genetics / Q000502:physiology*; D005407:Flagella / Q000235:genetics / Q000502:physiology*; D005408:Flagellin / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D055170:Plant Root Nodulation; D053204:Root Nodules, Plant / Q000382:microbiology* / Q000502:physiology; D013025:Glycine max / Q000382:microbiology* / Q000502:physiology; D013559:Symbiosis
chemical_list: D001426:Bacterial Proteins; D005408:Flagellin