Response of cbb gene transcription levels of four typical sulfur-oxidizing bacteria to the CO₂ concentration and its effect on their carbon fixation efficiency during sulfur oxidation

The variability in carbon fixation capability of four sulfur-oxidizing bacteria (Thiobacillus thioparus DSM 505, Halothiobacillus neapolitanus DSM 15147, Starkeya novella DSM 506, and Thiomonas intermedia DSM 18155) during sulfur oxidation was studied at low and high concentrations of CO₂. The mechanism underlying the variability in carbon fixation was clarified by analyzing the transcription of the cbb gene, which encodes the key enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase. DSM 15147 and DSM 505 fixed carbon more efficiently during sulfur oxidation than DSM 506 and DSM 18155 at 0.5% and 10% CO₂, which was mainly because their cbb gene transcription levels were much higher than those of DSM 506 and DSM 18155. A high CO₂ concentration significantly stimulated the carbon fixation efficiency of DSM 505 by greatly increasing the cbb gene transcription efficiency. Moreover, the influence of the CO₂ concentration on the carbon fixation efficiency of the four strains differed greatly during sulfur oxidation. Copyright © 2016 Elsevier Inc.