PDF(Pubmed)
Abstract：
Saltmarshes are highly productive environments, exhibiting high abundances of organosulfur compounds. Dimethylsulfoniopropionate (DMSP) is produced in large quantities by algae, plants, and bacteria and is a potential precursor for dimethylsulfoxide (DMSO) and dimethylsulfide (DMS). DMSO serves as electron acceptor for anaerobic respiration leading to DMS formation, which is either emitted or can be degraded by methylotrophic prokaryotes. Major products of these reactions are trace gases with positive (CO2, CH4) or negative (DMS) radiative forcing with contrasting effects on the global climate. Here, we investigated organic sulfur cycling in saltmarsh sediments and followed DMSO reduction in anoxic batch experiments. Compared to previous measurements from marine waters, DMSO concentrations in the saltmarsh sediments were up to ~300 fold higher. In batch experiments, DMSO was reduced to DMS and subsequently consumed with concomitant CH4 production. Changes in prokaryotic communities and DMSO reductase gene counts indicated a dominance of organisms containing the Dms-type DMSO reductases (e.g., Desulfobulbales, Enterobacterales). In contrast, when sulfate reduction was inhibited by molybdate, Tor-type DMSO reductases (e.g., Rhodobacterales) increased. Vibrionales increased in relative abundance in both treatments, and metagenome assembled genomes (MAGs) affiliated to Vibrio had all genes encoding the subunits of DMSO reductases. Molar conversion ratios of <1.3 CH4 per added DMSO were accompanied by a predominance of the methylotrophic methanogens Methanosarcinales. Enrichment of mtsDH genes, encoding for DMS methyl transferases in metagenomes of batch incubations indicate their role in DMS-dependent methanogenesis. MAGs affiliated to Methanolobus carried the complete set of genes encoding for the enzymes in methylotrophic methanogenesis.
摘要：
盐沼是高效的环境，表现出高丰度的有机硫化合物。二甲基磺丙酸盐（DMSP）是由藻类大量生产的，植物,和细菌，是二甲基亚砜（DMSO）和二甲基硫醚（DMS）的潜在前体。DMSO作为无氧呼吸的电子受体，导致DMS形成，可以释放或可以被甲基营养的原核生物降解。这些反应的主要产物是具有正（CO2，CH4）或负（DMS）辐射强迫的痕量气体，对全球气候具有相反的影响。这里,我们研究了盐沼沉积物中的有机硫循环，并在缺氧分批实验中遵循DMSO的减少。与以前的海洋水域测量相比，盐沼沉积物中的DMSO浓度高达约300倍。在批量实验中,将DMSO还原成DMS,随后伴随CH4产生而消耗。原核生物群落和DMSO还原酶基因计数的变化表明，含有Dms型DMSO还原酶的生物体占主导地位（例如，脱硫巴贝，肠杆菌)。相比之下,当硫酸盐还原被钼酸盐抑制时，Tor型DMSO还原酶(例如，红霉素）增加。弧菌在两种处理中的相对丰度增加，属于弧菌的宏基因组组装基因组（MAG）具有编码DMSO还原酶亚基的所有基因。每次添加的DMSO的摩尔转化率<1.3CH4伴随着占优势的甲基营养产甲烷菌甲烷。mtsDH基因的富集，在分批孵育的宏基因组中编码DMS甲基转移酶表明它们在DMS依赖性产甲烷中的作用。隶属于甲烷菌的MAG携带了一整套编码甲基营养甲烷生成酶的基因。
