Enrichment for Hydrogen-Oxidizing Acinetobacter spp. in the Rhizosphere of Hydrogen-Evolving Soybean Root Nodules.

Field soybean plants were inoculated with Hup wild-type or H(2) uptake-negative (Hup) mutants of Bradyrhizobium japonicum. For two consecutive summers we found an enrichment for acinetobacters associated with the surfaces of the H(2)-evolving nodules. Soybean root nodules that evolved H(2) had up to 12 times more Acinetobacter spp. bacteria associated with their surfaces than did nodules incapable of evolving H(2). All of the newly isolated strains identified as Acinetobacter obtained from the surfaces of root nodules, as well as known established Acinetobacter strains, were capable of oxidizing H(2), a property not previously described for this alkane-degrading soil bacterium.