Biology of anaerobic bacteria

Sulfate reducing bacteria of the genus DESULFOVIBRIO and homoacetogenic bacteria of the genus SPOROMUSA were sensitive to changes of hydrogen concentrations during the growth on an organic substrate. Increase of hydrogen concentrations competitively inhibited the organic substrate degradation and decrease of hydrogen concentration inhibited the respiration and the reduction of the external electron acceptor. Such hydrogen sensitive strains which seem to intermediarily produce and consume hydrogen ("hydrogen-cycling") were cultivated in the presence of a second hydrogen oxidizer. Both organisms competed for the hydrogen excreted by the first strain. The competence for H2-oxidation of the strains depended not only on hydrogenase affinities but also on the free energy change of H2-oxidation differing with the respective electron acceptors. (Résumé d'auteur