Hydrogen (h(2)) evolution by rhizobia after synergetic culture with soybean cell suspensions

Rhizobium japonicum cells were grown in liquid suspension cultures and separated from soybean plant cells by two to three bacterial membrane filters. Under these conditions, the plant cells elaborated materials into the medium which aided in the expression of a major rhizobial phenotype, namely, nitrogenase activity (acetylene reduction). The evolution of H(2) was also measured and this activity relative to acetylene reduction, was influenced by: (a) O(2); (b) the quantity of conditioned plant medium; and (c) ammonia. It is concluded that plant substances are of major importance in the H(2) evolution and nitrogenase activities of free-living rhizobia in suspension cultures.