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

Abstract The characteristics of carbon fixation of Halothiobacillus neapolitanus DSM 15147 with different concentrations of Na 2 S 2 O 3 ·5H 2 O as reduced sulfur were investigated. Moreover, the mechanisms underlying the carbon fixation characteristics in response to different Na 2 S 2 O 3 ·5H 2 O 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 Na 2 S 2 O 3 ·5H 2 O concentration, and the Na 2 S 2 O 3 ·5H 2 O oxidization amount and energy-releasing efficiency per unit of Na 2 S 2 O 3 ·5H 2 O were important reasons for the variation of carbon fixation efficiency at different Na 2 S 2 O 3 ·5H 2 O concentrations. Moreover, the cbb gene transcription efficiency and transcription pattern were also influenced by the Na 2 S 2 O 3 ·5H 2 O concentration, and when the Na 2 S 2 O 3 ·5H 2 O 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 Na 2 S 2 O 3 ·5H 2 O 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 CO 2 assimilation process by influencing the cbb gene transcription efficiency.