Influence of reduced sulfur on carbon fixation efficiency of Halothiobacillus neapolitanus and its mechanism

The characteristics of carbon fixation of Halothiobacillus neapolitanus DSM 15147 with different concentrations of Na₂S₂O₃·5H₂O as reduced sulfur were investigated. Moreover, the mechanisms underlying the carbon fixation characteristics in response to different Na₂S₂O₃·5H₂O concentrations were clarified from the energy supply perspectives and the cbb gene transcription characteristics. The results showed that the carbon fixation efficiency of H. neapolitanus was influenced by the Na₂S₂O₃·5H₂O concentration, and the Na₂S₂O₃·5H₂O oxidization amount and energy-releasing efficiency per unit of Na₂S₂O₃·5H₂O were important reasons for the variation of carbon fixation efficiency at different Na₂S₂O₃·5H₂O concentrations. Moreover, the cbb gene transcription efficiency and transcription pattern were also influenced by the Na₂S₂O₃·5H₂O concentration, and when the Na₂S₂O₃·5H₂O concentration was too low or too high, it was not conducive to the cbb gene transcription process, thus resulting in the relatively low carbon fixation efficiency. Furthermore, low Na₂S₂O₃·5H₂O concentration was not beneficial to the cytoskeleton synthesis due to the insufficient energy supply and further resulted in the accumulation of extracellular free organic matters, which might induce a feedback inhibitory effect on the CO₂ assimilation process by influencing the cbb gene transcription efficiency. Copyright © 2017 Elsevier B.V.