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<p>Sulfide oxidation and sulfate reduction are opposing processes in the microbial sulfur cycle, typically separated to avoid futile cycling. Here, we show that <i>Mycobacterium</i> sp. MAG-M116, identified from a biodesulfurization system under low pH, sulfate-rich, and H<sub>2</sub>S-overload conditions, simultaneously performs sulfide oxidation and assimilatory sulfate reduction (ASR), challenging this paradigm. Under aerobic conditions, MAG-M116 oxidizes sulfide to elemental sulfur, channeling electrons into the quinone pool to drive forward electron transfer for ATP synthesis and reverse electron transfer (RET) for NADPH generation. ASR, acting as a redox homeostat, captures electrons from leak-prone RET to mitigate electron leakage and reduce reactive oxygen species production by 57.5%. This bidirectional sulfur metabolism enables rapid sulfide detoxification while maintaining intracellular redox homeostasis, allowing <i>Mycobacterium</i> to dominate the community (abundance increasing from 3.5% to 99%). These findings reveal an adaptive strategy wherein coupled opposing redox reactions contribute to maintaining intracellular redox homeostasis under substrate-excess conditions.</p>

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Simultaneous sulfide oxidation and sulfate reduction for intracellular redox homeostasis under highly acidic conditions

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年1月19日

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  • Tipei Jia,
  • Yongzhen Peng,
  • Lishan Niu,
  • Zheng Qi,
  • Jinying Xi

摘要

Sulfide oxidation and sulfate reduction are opposing processes in the microbial sulfur cycle, typically separated to avoid futile cycling. Here, we show that Mycobacterium sp. MAG-M116, identified from a biodesulfurization system under low pH, sulfate-rich, and H2S-overload conditions, simultaneously performs sulfide oxidation and assimilatory sulfate reduction (ASR), challenging this paradigm. Under aerobic conditions, MAG-M116 oxidizes sulfide to elemental sulfur, channeling electrons into the quinone pool to drive forward electron transfer for ATP synthesis and reverse electron transfer (RET) for NADPH generation. ASR, acting as a redox homeostat, captures electrons from leak-prone RET to mitigate electron leakage and reduce reactive oxygen species production by 57.5%. This bidirectional sulfur metabolism enables rapid sulfide detoxification while maintaining intracellular redox homeostasis, allowing Mycobacterium to dominate the community (abundance increasing from 3.5% to 99%). These findings reveal an adaptive strategy wherein coupled opposing redox reactions contribute to maintaining intracellular redox homeostasis under substrate-excess conditions.