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

Abstract

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.