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Abstract
N2-fixing Azospirillum brasilense possesses an H2-uptake hydrogenase activity capable of supporting H2-dependent acetylene reduction by whole cells starved of carbon metabolites. H2 did not support acetylene reduction in carbon-sufficient bacteria. although carbon substrates did not inhibit H2-dependent respiration. H2-dependent respiration was extremely O2 sensitive and could not usually protect nitrogenase against inhibition by O2. H2 partly inhibited nitrogenase activity at sub-optimal O2 concentrations: this may be because H2-dependent respiration has a greater affinity for O2 but is less efficiently coupled to ATP production than is carbon-dependent respiration.
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© Society for General Microbiology, 1982