Summary: Pseudomonas saccharophila Doudoroff (ATCC 15946) reduced C2H2 and fixed 15N2 heterotrophically in N-free semi-solid medium supplemented with 100 mg yeast extract l−1. Nitrogenase activity was markedly stimulated by addition of sugars and organic acids and was expressed microaerobically. Autotrophically-grown cells showed nitrogenase activity. This is the first report of N2 fixation in a well-characterized Pseudomonas species capable of chemoautotrophic growth with H2 as the electron donor.
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