The CO2 assimilation via the reductive tricarboxylic acid cycle in an obligately autotrophic, aerobic hydrogen-oxidizing bacterium, Hydrogenobacter thermophilus

The incorporation of 14CO2 by the cell suspensions of an extremely thermophilic, aerobic hydrogen-oxidizing bacterium, Hydrogenobacter thermophilus was studied. After short time incubation of the cell suspensions with 14CO2, the radiactivity was initially present in aspartate, glutamate, succinate, phosphorylated compounds, citrate, malate and fumarate. All of these compounds except phosphorylated compounds were related to the members of the tricarboxylic acid cycle. The proportion of labelled aspartate onglutamate in total radioactivity on each chromatogram decreased with incubation time, while the percentage of the radioactivity incorporated in phosphorylated compounds increased with time up to 10 s. These indicated that aspartate and glutamate is derived from primary products of CO2 fixation.