NITROGEN FIXATION AND HYDROGENASE IN VARIOUS BACTERIAL SPECIES

Abstract

N fixation was demonstrated by Kjeldahl and isotopic analyses by five members of the family Athiorhodaceae (Rhodospirillum sp., Rhodopseudomonas capsulatus, R. spheroides, R. gelatinosa, and R. palustris). 19 strains of rhodopseudomonads were shown to fix N2 Rhodomicrobium vannielii, an unassigned photosynthetic bacterium, was also demonstrated to fix N2. Two non-photosynthetic hydrogenase-possessing species, Escherichia coli and Hydrogenomonas sp., were tested for fixation using N215; neither fixed N2 under the conditions employed. Although most organisms able to fix N2 possess hydrogenase, presence of this enzyme system does not imply that an organism can fix N2.