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

- Na2S2O3·5H2O affects the CO2 fixation efficiency of Halothiobacillus neapolitanus.
- The various CO2 fixing efficiency was greatly related to energy-releasing efficiency.
- The cbb gene transcription efficiency and pattern were affected by Na2S2O3·5H2O.
- EFOC might induce a feedback inhibitory effect on CO2 fixation at low Na2S2O3·5H2O.

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.

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