Frank Joshua, Zhang Xueqin, Marcellin Esteban, Yuan Zhiguo, Hu Shihu
Australian Centre for Water and Environmental Biotechnology (ACWEB), Faculty of Engineering, Architecture and Information Technology, The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia.
Australian Centre for Water and Environmental Biotechnology (ACWEB), Faculty of Engineering, Architecture and Information Technology, The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia.
Water Res. 2023 Aug 15;242:120090. doi: 10.1016/j.watres.2023.120090. Epub 2023 May 17.
Nitrate-dependent anaerobic methane oxidation (AOM) is a microbial process of both ecological significance for global methane mitigation and application potential for wastewater treatment. It is mediated by organisms belonging to the archaeal family 'Candidatus Methanoperedenaceae', which have so far mainly been found in freshwater environments. Their potential distribution in saline environments and their physiological responses to salinity variation were still poorly understood. In this study, the responses of the freshwater 'Candidatus Methanoperedens nitroreducens'-dominated consortium to different salinities were investigated using short- and long-term setups. Short-term exposure to salt stress significantly affected nitrate reduction and methane oxidation activities over the tested concentration range of 15-200‰ NaCl, and 'Ca. M. nitroreducens' showed the higher tolerance to high salinity stress than its partner of anammox bacteria. At high salinity concentration, near marine conditions of 37‰, the target organism 'Ca. M. nitroreducens' showed stabilized nitrate reduction activity of 208.5 µmol day g in long-term bioreactors over 300 days, in comparison to 362.9 and 334.3 µmol day g under low-salinity conditions (1.7‰ NaCl) and control conditions (∼15‰ NaCl). Different partners of 'Ca. M. nitroreducens' evolved in the consortia with three different salinity conditions, suggesting the different syntrophic mechanisms shaped by changes in salinity. A new syntrophic relationship between 'Ca. M. nitroreducens' and Fimicutes and/or Chloroflexi denitrifying populations was identified under the marine salinity condition. Metaproteomic analysis shows that the salinity changes lead to higher expression of response regulators and selective ion (Na/H) channeling proteins that can regulate the osmotic pressure between the cell and its environment. The reverse methanogenesis pathway was, however, not impacted. The finding of this study has important implications for the ecological distribution of the nitrate-dependent AOM process in marine environments and the potential of this biotechnological process for the treatment of high-salinity industrial wastewater.
依赖硝酸盐的厌氧甲烷氧化（AOM）是一个具有全球甲烷减排生态意义和废水处理应用潜力的微生物过程。它由属于古菌“嗜甲基甲烷氧化菌科（Candidatus Methanoperedenaceae）”的生物体介导，到目前为止，这些生物体主要在淡水环境中被发现。它们在盐环境中的潜在分布以及对盐度变化的生理反应仍知之甚少。在本研究中，使用短期和长期设置研究了以淡水“嗜甲基甲烷氧化还原菌（Candidatus Methanoperedens nitroreducens）”为主的菌群对不同盐度的反应。在15 - 200‰ NaCl的测试浓度范围内，短期暴露于盐胁迫显著影响硝酸盐还原和甲烷氧化活性，并且“嗜甲基甲烷氧化还原菌（Ca. M. nitroreducens）”比其厌氧氨氧化细菌伙伴对高盐胁迫表现出更高的耐受性。在高盐浓度（接近海洋条件的37‰）下，目标生物体“嗜甲基甲烷氧化还原菌（Ca. M. nitroreducens）”在长期生物反应器中300多天内显示出稳定的硝酸盐还原活性为208.5 μmol·天·克，相比之下，在低盐度条件（1.7‰ NaCl）和对照条件（约15‰ NaCl）下分别为362.9和334.3 μmol·天·克。“嗜甲基甲烷氧化还原菌（Ca. M. nitroreducens）”的不同伙伴在三种不同盐度条件的菌群中进化，表明盐度变化塑造了不同的互营机制。在海洋盐度条件下，确定了“嗜甲基甲烷氧化还原菌（Ca. M. nitroreducens）”与厚壁菌门和/或绿弯菌门反硝化菌群之间的一种新的互营关系。元蛋白质组分析表明，盐度变化导致响应调节因子和选择性离子（Na/H）通道蛋白的表达增加，这些蛋白可以调节细胞与其环境之间的渗透压。然而，反向产甲烷途径未受影响。本研究的发现对于依赖硝酸盐的AOM过程在海洋环境中的生态分布以及该生物技术过程处理高盐工业废水的潜力具有重要意义。
