Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW, Australia.
Department of Molecular Biology and Genetics, Istanbul University, Istanbul, Turkey.
ISME J. 2021 Jun;15(6):1709-1721. doi: 10.1038/s41396-020-00881-y. Epub 2021 Jan 15.
Dichloromethane (DCM; CHCl) is a toxic groundwater pollutant that also has a detrimental effect on atmospheric ozone levels. As a dense non-aqueous phase liquid, DCM migrates vertically through groundwater to low redox zones, yet information on anaerobic microbial DCM transformation remains scarce due to a lack of cultured organisms. We report here the characterisation of DCMF, the dominant organism in an anaerobic enrichment culture (DFE) capable of fermenting DCM to the environmentally benign product acetate. Stable carbon isotope experiments demonstrated that the organism assimilated carbon from DCM and bicarbonate via the Wood-Ljungdahl pathway. DCMF is the first anaerobic DCM-degrading population also shown to metabolise non-chlorinated substrates. It appears to be a methylotroph utilising the Wood-Ljungdahl pathway for metabolism of methyl groups from methanol, choline, and glycine betaine. The flux of these substrates from subsurface environments may either directly (DCM, methanol) or indirectly (choline, glycine betaine) affect the climate. Community profiling and cultivation of cohabiting taxa in culture DFE without DCMF suggest that DCMF is the sole organism in this culture responsible for substrate metabolism, while the cohabitants persist via necromass recycling. Genomic and physiological evidence support placement of DCMF in a novel genus within the Peptococcaceae family, 'Candidatus Formimonas warabiya'.
二氯甲烷（DCM；CHCl）是一种有毒的地下水污染物，对大气臭氧水平也有不利影响。作为一种致密的非水相液体，DCM 通过地下水垂直迁移到低氧化还原区，但由于缺乏培养的生物体，关于厌氧微生物 DCM 转化的信息仍然很少。我们在这里报告了 DCMF 的特征，DCMF 是一种能够将 DCM 发酵为环境友好产物醋酸盐的厌氧富集培养物（DFE）中的主要生物体。稳定碳同位素实验表明，该生物体通过 Wood-Ljungdahl 途径从 DCM 和碳酸氢盐中同化碳。DCMF 是第一个被证明能够代谢非氯化底物的厌氧 DCM 降解种群。它似乎是一种利用 Wood-Ljungdahl 途径代谢甲醇、胆碱和甘氨酸甜菜碱中甲基的甲基营养菌。这些底物从地下环境中的通量可能直接（DCM、甲醇）或间接（胆碱、甘氨酸甜菜碱）影响气候。在没有 DCMF 的培养 DFE 中进行的共生物种的群落分析和培养表明，DCMF 是该培养物中唯一负责基质代谢的生物体，而共生物种则通过腐殖质循环持续存在。基因组和生理证据支持将 DCMF 置于 Peptococcaceae 科内的一个新属“Candidatus Formimonas warabiya”中。
