Impact of microorganisms as sinks of atmospheric chloromethane

由两个法国伙伴和两个德国伙伴组成的跨学科联盟将结合他们的专业知识和知识，解决微生物对全球氯甲烷（CH3Cl）预算的影响。自1989年《蒙特利尔议定书》生效以来，人为排放的消耗臭氧化合物（CFcs）已大幅减少。因此，从天然来源释放的化合物，如CH3Cl，与平流层臭氧消耗的关系日益密切。这种氯化气体是大气中含量最多的卤化化合物，其主要来源是陆地生态系统。活的和死的植被和生物质燃烧释放是主要来源。与温度的正线性响应表明，未来变暖的气候可能导致CH3Cl排放增加。然而，目前对CH3Cl全球预算的估计是不确定的，并且表明微生物在降解大气CH3Cl方面发挥的作用比以前认为的更重要。甲基营养微生物，一些具有代谢降解CH3Cl的能力，存在于土壤中，许多植物的层层中，并且最近被报道在云的水滴中活跃。申请人认为，拟议项目的主要目标是揭示过程层面的定量信息，并提供对这些微生物的深入遗传见解。该联盟将研究与土壤、植物和云相关的甲基营养体降解CH3Cl过程中的动力学和同位素效应。将对特定的CH3Cl降解甲基营养体进行实验室实验，以测量它们对同位素组成的影响，并确定温度对动力学参数的影响。在各种环境样品中，微生物群落将使用扩增子靶向下一代测序，采用分类学（16S RNA基因）和CH3Cl降解（cmuA）功能基因标记。选择土壤、植物和云水样品进行CH3Cl的13c -同位图，以标记CH3Cl转化微生物的生物量。然后将使用DNA稳定同位素探测、全基因组扩增和MiSeq （Illumina）高通量测序的组合来检索宏基因组。这些实验将评估微生物CH3Cl降解途径的多样性，并将使发现新的甲基转移酶和进一步参与CH3Cl代谢转化的基因成为可能。宏基因组方法将为温带陆地生态系统和云的ch3cl降解微生物群落提供新的见解。动力学和同位素数据将解决微生物汇与全球CH3Cl收支的定量相关性。提高对大气CH3Cl源和汇的定量认识对于提高我们对平流层氯化学和臭氧层稳定性的预测能力将是非常宝贵的。

An interdisciplinary consortium of two French and two German partners will combine their expertise and knowledge to address the impact of microorganisms on the global budget of chloromethane (CH3Cl). Anthropogenic emissions of ozone depleting compounds (CFcs) have been strongly reduced since the Montreal protocol came into force in 1989. As a consequence, compounds released from natural sources, such as CH3Cl, have become increasingly relevant in stratospheric ozone depletion. This chlorinated gas is the most abundant halogenated compound in the atmosphere whose primarily source is the terrestrial ecosystems. Release from living and dead vegetation and biomass burning are major sources. The positive linear response with temperature suggests that future warmer climates will likely lead to increased CH3Cl emissions. However, current estimates of the CH3Cl global budget are uncertain and suggest that microorganisms play a more important role in degrading atmospheric CH3Cl than previously thought. Methylotrophic microbes, some with the metabolic capability to degrade CH3Cl, occur in soils, the phyllosphere of many plants, and have recently been reported to be active in water droplets of clouds. The applicants conceive that the main objectives of the proposed project are to reveal quantitative information on process-level and to provide in depth genetic insights into these microbes. The consortium will investigate kinetic and isotope effects during CH3Cl degradation by methylotrophs associated with soils, plants, and clouds. Laboratory experiments with specific CH3Cl degrading methylotrophs will be conducted to measure their effects on isotope composition and to determine temperature effects on kinetic parameters. In various environmental samples the microbial community will be characterized using amplicon-targeted next generation sequencing employing a taxonomical (16S RNA genes) and a functional gene marker for CH3Cl degradation (cmuA). Selected samples of soil, plants, and cloud water will be subjected to 13C-isoptopologue of CH3Cl in order to label the biomass of CH3Cl converting microbes. Metagenomes will then be retrieved using a combination of DNA stable isotope probing, whole genome amplification, and MiSeq (Illumina) high throughput sequencing. These experiments will assess the diversity of the microbial CH3Cl-degrading pathways, and will enable the discovery of novel methyltransferases and further genes involved in CH3Cl metabolic transformation. The metagenomic approach will provide new insights into CH3Cl-degrading microbial communities of temperate terrestrial ecosystems and clouds. Kinetic and isotopic data will resolve the quantitative relevance of microbial sinks for the global CH3Cl budget. A improved quantitative understanding of the sources and sinks of atmospheric CH3Cl will be invaluable for enhancing our predictive capability for stratospheric chlorine chemistry and ozone layer stability.