Anaerobic nitrate-dependent chemolithotrophic growth by Rhizobium japonicum

Abstract
A hydrogen-uptake-positive strain of Rhizobium japonicum (6-3I1b6) was demonstrated to grow in absence of oxygen chemolithotrophically, utilizing nitrate as the electron acceptor. Dissimilatory nitrate reduction occurred during growth, as evidenced by the disappearance of nitrate from the medium and production of nitrous oxide. Rhizobium japonicum 120-3I1b120, a hydrogen-uptake-negative strain, showed little or no growth under anaerobic chemolithotrophic growth conditions and did not evolve nitrous oxide. A nitrate-dependent hydrogen-uptake and an oxygen-dependent hydrogen-uptake system was present in cells of strain 6-3I1b6 grown chemolithotrophically under anaerobic conditions with nitrate serving as the electron acceptor.