Cruising the marine halomethane cycle: Microbiology, biochemistry and geochemistry of reference bacteria, new microbial players and underlying processes

挥发性有机卤化物对生物体有毒。此外，它们还有助于破坏平流层臭氧。海洋是这些化合物的主要来源，主要包括卤代甲烷（氯甲烷、溴甲烷和碘甲烷）。它们由微生物和藻类产生，但也代表细菌生命的营养物质。卤代甲烷的源和汇及其在海洋环境和大气中产生的通量的特征仍然很差。特别是，到目前为止，只有一种微生物降解氯甲烷的途径得到了阐明，尽管文献中的许多研究清楚地表明存在其他途径。为期36个月的法德研究项目MAHABIO的目标是全面了解挥发性卤代化合物的全球生物化学循环。它提出了一个坚定的跨学科，创新和紧密关注的方法来探索和表征与海洋环境中氯甲烷的生产和消费相关的细菌过程。MAHABIO与两个法国和两个德国合作伙伴合作，每个合作伙伴都带来了互补的专业领域。 该项目分为三个工作包：一）研究海洋样品的氯甲烷消耗情况，并对参考菌株涉及的脱卤酶进行表征，包括在迄今被忽视的缺氧条件下进行的研究;二）对海洋样品中的细菌和参考菌株产生的氯甲烷进行量化;三）对合成细菌群落产生和消耗氯甲烷的情况进行综合研究。MAHABIO合作伙伴的协同专业知识是该项目的关键资产。此外，该项目的许多先决条件已在初步实验中得到验证。这些研究包括海洋氯甲烷降解菌的培养、氯甲烷三要素的稳定同位素分析以及一株海洋氯甲烷降解菌利用氯甲烷的初步遗传学和蛋白质组学研究。对项目每个方面的深入分析也使我们能够明确地确定相关风险，并提出后备解决方案。MAHABIO设想在氯甲烷的生产和消费方面取得重大科学和技术进步，例如所涉及的新型细菌酶的生物化学、酶和遗传特性，以及建立与氯甲烷生产和消费有关的特征生物标志物和同位素特征。总之，预期的结果将有助于开发更新的最先进的技术，有助于更好地了解全球地球化学循环。

Volatile organohalides are toxic to living organisms. Furthermore, they contribute to the destruction of stratospheric ozone. Seas and oceans are major sources of these compounds that prominently comprise halomethanes (chloro-, bromo-, and iodomethane). They are produced by microorganisms and algae but also represent nutrients for bacterial life. The sources and sinks of halomethanes, as well as their resulting fluxes in the marine environment and the atmosphere, remain poorly characterized. In particular, only one pathway for microbial degradation of chloromethane has been elucidated so far, although many studies in the literature clearly suggest that others exist.The 36-month French-German research project MAHABIO ambitions to gain a comprehensive view on global biogeochemical cycles of volatile halogenated compounds. It proposes a resolutely interdisciplinary, innovative, and tightly focussed approach to explore and characterize bacterial processes associated with production and consumption of chloromethane in the marine environment. MAHABIO associates two French and two German partners, each bringing complementary areas of expertise. It is organized in three work packages : i) study of chloromethane consumption by marine samples and characterization of dehalogenases involved from reference strains, including under hitherto neglected anoxic conditions; ii) quantification of bacterial production of chloromethane in marine samples and by reference bacterial strains; and iii) integrative study of concomitant production and consumption of chloromethane by synthetic bacterial communities. The synergistic expertise of MAHABIO partners is a key asset of the project. In addition, many prerequisites for this project have been validated in preliminary experiments. These include cultivation of marine chloromethane-degrading bacteria, stable isotope analysis with the three elements of chloromethane, and preliminary genetic and proteomic characterization of chloromethane utilization by a marine chloromethane-degrading bacterium with yet uncharacterized pathway. In-depth analysis of each aspect of the project has also made it possible to explicitly identify associated risks, and to propose fallback solutions. Major scientific and technological advances are envisaged from MAHABIO in the production and consumption of chloromethane such as the biochemical, enzymatic and genetic characterization of novel bacterial enzymes involved, and the establishment of characteristic biomarkers and isotopic signatures associated with chloromethane production and consumption. Taken together, the expected results will contribute in developing renewed, state-of-the-art technologies that contribute to a better understanding of global biogeochemical cycles.