Biogeochemistry of carbon monoxide cycling in hypersaline and arid soil systems: novel insights from newly discovered extremely halophilic CO-oxidizing Euryarchaeota

广泛的研究表明，土壤是微量气体的主要来源和汇，在大气化学和全球气候制度中发挥重要作用。然而，大多数研究都集中在森林、草地和耕地土壤上，这些土壤在很大程度上经历了温和的条件（例如温度和降水）。占全球陆地总面积约三分之一的干旱和半干旱土壤受到的关注相对较少。盐碱地的面积比法国还大，约占农业用地总面积的18%，但也被忽视了。尽管如此，最近对干旱和盐碱地的研究结果表明，它们可能对区域尺度上的一氧化碳（CO）的全球预算做出重大贡献，一氧化碳是一种微量气体，在大气中具有关键的调节功能。这里提出的研究将包括对犹他州、加利福尼亚州和俄克拉何马州盐碱地和干旱土壤中CO循环的比较研究，对干旱和盐碱地从大气中去除CO的能力的分析，以及对土壤基质中CO去除和生产之间耦合的分析。这些结果将与微生物群落和CO氧化微生物的平行研究相辅相成，将为地球土壤的一个主要类别提供对CO生物地球化学的全面了解。这里提出的工作将涉及多个任务。将通过通量研究、土壤和沉积物培养等实验室实验来探讨依赖钼的CO氧化和缺氧CO产生之间的耦合程度，以及两者在高盐CO循环中的作用，这些实验旨在探测氧化和产生的速率以及所涉及的生物体。关于支持CO氧化的条件范围的新见解将来自对水可用性的大范围极端活动的分析；土壤和沉积物的移地分析和台式分析都将用于评估CO氧化的极限。溶质应力与基质电位应力的重要性将通过在一系列相似水势范围内对盐碱化系统和干旱系统进行比较来确定。最后，来自新的和现有的CO氧化分离株的基因组数据将用于建立mo依赖的CO氧化的进化史和其起源的地理生物学背景。这个项目将涉及研究生和本科生在项目的几个阶段。威斯敏斯特学院和犹他大学的学生将参与实地研究，并接受生物地球化学和微生物多样性分析方面的培训。此外，来自路易斯安那州立大学“排序校园”计划的学生将参与该项目。PI将通过路易斯安那州立大学的环境分会进一步努力招收代表性不足的学生。

Extensive research has shown that soils are major sources and sinks of trace gases that play important roles in atmospheric chemistry and global climate regimes. However, most of this research has focused on forest, grassland and cultivated soils that largely experience moderate conditions (e.g., temperature and precipitation). Arid and semi-arid soils, which account for about one-third of total global land area, have received relatively little attention. Saline soils, which account for an area larger than France, and constitute about 18% of total agricultural land area, have been also been overlooked. Nonetheless, results of recent work with arid and saline soils indicates that they may contribute significantly to regional-scale to global budgets of carbon monoxide (CO), a trace gas that has critical regulatory functions in the atmosphere. Research proposed here will include comparative studies of CO cycling in saline and arid soils in Utah, California and Oklahoma, analyses of the capacity of arid and saline soils to remove CO from the atmosphere, and analyses of the coupling between CO removal and production within the soil matrix. The results, which will be complemented by parallel studies of microbial communities and CO-oxidizing microbes, will provide a comprehensive understanding of CO biogeochemistry for a major category of Earth's soils. Work proposed here will involve multiple tasks. The extent of coupling between Mo-dependent CO oxidation and anoxic CO production, and the roles of each in hypersaline CO cycling will be addressed through flux studies and soil and sediment incubations in laboratory experiments designed to probe rates of oxidation and production as well as the organisms involved. New insights about the range of conditions that support CO oxidation will be derived from analyses of activity across a wide range of extremes in water availability; both ex situ and bench-top analyses of soils and sediments will be used to assess limits of CO oxidation. The importance of solute stresses versus matric potential stresses will be determined by comparisons of saline and arid systems across a range of similar water potentials. Finally, genomic data from new and existing CO-oxidizing isolates will be used to establish an evolutionary history for Mo-dependent CO oxidation and a geobiological context for its origin. This project will involve graduate and undergraduate students in several stages of the project. Students of Westminster College and University of Utah will be involved with field research, and receive training on biogeochemistry and microbial diversity analysis. In addition, students from the "Sequence the Campus" program of the Louisiana State University will be involved in the project. The PI will make additional efforts to recruit under-represented students through LSU's EnvironMentors Chapter.