Predominance of hydrogen-utilizing bacteria among N₂-fixing bacteria in wetland rice roots

Abstract

Heterotrophic bacteria were isolated from wetland soil, rhizosphere soil, root and basal shoot of wetland rice, dryland soil, and root of dryland rice. The isolates were tested for N 2 -fixing activity and the ability to grow autotrophically under H 2 + CO 2 + O 2 . N 2 -fixing bacteria capable of autotrophic growth were found almost exclusively from the rhizosphere and the root of wetland rice. In another experiment, all N 2 -fixing bacteria isolated from wetland rice root had uptake hydrogenase activity. These findings indicate the predominance of hydrogen-utilizing bacteria among N 2 -fixing bacteria from wetland rice roots.