Organohalide-Respiring Bacteria at the Heart of Anaerobic Metabolism in Arctic Wet Tundra Soils
Organohalide-Respiring Bacteria at the Heart of Anaerobic Metabolism in Arctic Wet Tundra Soils
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DOI：
10.1128/aem.01643-20
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发表时间：
2020-11
影响因子：
4.4
通讯作者：
D. Lipson;T. Raab;Sherlynette Pérez Castro;Alexander Powell
中科院分区：
文献类型：
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作者：
D. Lipson;T. Raab;Sherlynette Pérez Castro;Alexander Powell
曾经认为仅与受污染场地有关，现在认识到生物氯循环在自然环境中广泛存在。然而，氯循环和其他生态系统过程之间的联系尚未得到很好的确立。摘要最近的研究表明，在阿拉斯加北方沿海的北极苔原上存在着活跃的生物氯循环。这就提出了一个问题，即氯循环是否仅限于沿海地区，或者这些过程是否延伸到内陆苔原。有机卤化物呼吸的厌氧过程由专门的细菌如Dehalococcoides进行，使用卤化有机化合物作为末端电子受体消耗氢气和乙酸盐，可能与产生温室气体甲烷的产甲烷菌竞争。我们测量微生物群落组成和土壤化学沿着262公里的海岸-内陆样带，以测试整个北极沿海平原的有机卤化物呼吸的潜力，并研究了与Dehalococcoides相关的微生物群落，以探索这一群体的生态及其影响北极碳循环的潜力。溴化有机化合物的浓度随着远离海岸而急剧下降，但有机氯池的减少更为微妙。整个样带中Dehalococcoides的相对丰度相似，只是在最内陆的地点较低。Dehalococcoides与其他严格厌氧的属，加上一些兼性的，有遗传潜力，提供必要的资源（氢，乙酸，corrinoids，或有机氯）。该群落包括铁还原菌、硫酸盐还原菌、互养菌、产乙酸菌和产甲烷菌，其中一些也可能与Dehalococcoides竞争氢和乙酸盐。在整个北极沿海平原，Dehalococcoides与控制氢、乙酸盐、甲烷和二氧化碳通量的优势厌氧菌有关。根据季节性电子受体的可用性，有机卤化物呼吸细菌可能会影响北极潮湿苔原土壤的碳循环。重要性曾经认为仅在受污染的场地相关，现在认识到，生物氯循环在自然环境中广泛存在。然而，氯循环和其他生态系统过程之间的联系尚未得到很好的确立。Dehalococcoides属的物种是高度专业化的，使用周围社区产生的氢，乙酸盐，维生素B12样化合物和有机氯。我们研究了哪些邻居可能为Dehalococcoides物种提供这些必要的资源。我们发现，Dehalococcoides物种在北极沿海平原无处不在，并与产生或消耗氢或乙酸盐的微生物网络密切相关，包括最丰富的厌氧细菌和产甲烷古菌。我们还发现了有机氯和微生物，可以在整个研究区域产生这些化合物。因此，当合适的有机氯化合物可用于驱动氢和乙酸盐吸收时，Dehalococcoides可以控制二氧化碳和甲烷（一种更有效的温室气体）之间的平衡。
Once considered relevant only in contaminated sites, it is now recognized that biological chlorine cycling is widespread in natural environments. However, linkages between chlorine cycling and other ecosystem processes are not well established. ABSTRACT Recent work revealed an active biological chlorine cycle in coastal Arctic tundra of northern Alaska. This raised the question of whether chlorine cycling was restricted to coastal areas or if these processes extended to inland tundra. The anaerobic process of organohalide respiration, carried out by specialized bacteria like Dehalococcoides, consumes hydrogen gas and acetate using halogenated organic compounds as terminal electron acceptors, potentially competing with methanogens that produce the greenhouse gas methane. We measured microbial community composition and soil chemistry along an ∼262-km coastal-inland transect to test for the potential of organohalide respiration across the Arctic Coastal Plain and studied the microbial community associated with Dehalococcoides to explore the ecology of this group and its potential to impact C cycling in the Arctic. Concentrations of brominated organic compounds declined sharply with distance from the coast, but the decrease in organic chlorine pools was more subtle. The relative abundances of Dehalococcoides were similar across the transect, except for being lower at the most inland site. Dehalococcoides correlated with other strictly anaerobic genera, plus some facultative ones, that had the genetic potential to provide essential resources (hydrogen, acetate, corrinoids, or organic chlorine). This community included iron reducers, sulfate reducers, syntrophic bacteria, acetogens, and methanogens, some of which might also compete with Dehalococcoides for hydrogen and acetate. Throughout the Arctic Coastal Plain, Dehalococcoides is associated with the dominant anaerobes that control fluxes of hydrogen, acetate, methane, and carbon dioxide. Depending on seasonal electron acceptor availability, organohalide-respiring bacteria could impact carbon cycling in Arctic wet tundra soils. IMPORTANCE Once considered relevant only in contaminated sites, it is now recognized that biological chlorine cycling is widespread in natural environments. However, linkages between chlorine cycling and other ecosystem processes are not well established. Species in the genus Dehalococcoides are highly specialized, using hydrogen, acetate, vitamin B12-like compounds, and organic chlorine produced by the surrounding community. We studied which neighbors might produce these essential resources for Dehalococcoides species. We found that Dehalococcoides species are ubiquitous across the Arctic Coastal Plain and are closely associated with a network of microbes that produce or consume hydrogen or acetate, including the most abundant anaerobic bacteria and methanogenic archaea. We also found organic chlorine and microbes that can produce these compounds throughout the study area. Therefore, Dehalococcoides could control the balance between carbon dioxide and methane (a more potent greenhouse gas) when suitable organic chlorine compounds are available to drive hydrogen and acetate uptake.