State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, 266237, China.
College of Marine Life Sciences, Institute for Advanced Ocean Study, Ocean University of China, Qingdao, 266003, China.
Microbiome. 2021 Oct 16;9(1):207. doi: 10.1186/s40168-021-01153-3.
Dimethyl sulfide (DMS) is the dominant volatile organic sulfur in global oceans. The predominant source of oceanic DMS is the cleavage of dimethylsulfoniopropionate (DMSP), which can be produced by marine bacteria and phytoplankton. Polar oceans, which represent about one fifth of Earth's surface, contribute significantly to the global oceanic DMS sea-air flux. However, a global overview of DMS and DMSP cycling in polar oceans is still lacking and the key genes and the microbial assemblages involved in DMSP/DMS transformation remain to be fully unveiled.
Here, we systematically investigated the biogeographic traits of 16 key microbial enzymes involved in DMS/DMSP cycling in 60 metagenomic samples from polar waters, together with 174 metagenome and 151 metatranscriptomes from non-polar Tara Ocean dataset. Our analyses suggest that intense DMS/DMSP cycling occurs in the polar oceans. DMSP demethylase (DmdA), DMSP lyases (DddD, DddP, and DddK), and trimethylamine monooxygenase (Tmm, which oxidizes DMS to dimethylsulfoxide) were the most prevalent bacterial genes involved in global DMS/DMSP cycling. Alphaproteobacteria (Pelagibacterales) and Gammaproteobacteria appear to play prominent roles in DMS/DMSP cycling in polar oceans. The phenomenon that multiple DMS/DMSP cycling genes co-occurred in the same bacterial genome was also observed in metagenome assembled genomes (MAGs) from polar oceans. The microbial assemblages from the polar oceans were significantly correlated with water depth rather than geographic distance, suggesting the differences of habitats between surface and deep waters rather than dispersal limitation are the key factors shaping microbial assemblages involved in DMS/DMSP cycling in polar oceans.
Overall, this study provides a global overview of the biogeographic traits of known bacterial genes involved in DMS/DMSP cycling from the Arctic and Antarctic oceans, laying a solid foundation for further studies of DMS/DMSP cycling in polar ocean microbiome at the enzymatic, metabolic, and processual levels. Video Abstract.
二甲基硫（DMS）是全球海洋中主要的挥发性有机硫。海洋中二甲基硫丙酸酯（DMSP）的裂解是海洋 DMS 的主要来源，而 DMSP 可以由海洋细菌和浮游植物产生。极地海洋约占地球表面的五分之一，对全球海洋 DMS 的海-气通量有重要贡献。然而，极地海洋中二甲基硫和二甲基硫丙酸酯循环的全球概述仍然缺乏，而涉及 DMSP/DMS 转化的关键基因和微生物组合仍有待充分揭示。
在这里，我们系统地研究了 60 个极地水样中 16 种参与 DMS/DMSP 循环的关键微生物酶的生物地理特征，同时还研究了来自非极地 Tara 海洋数据集的 174 个宏基因组和 151 个宏转录组。我们的分析表明，强烈的 DMS/DMSP 循环发生在极地海洋中。DMSP 脱甲基酶（DmdA）、DMSP 裂解酶（DddD、DddP 和 DddK）和三甲胺单加氧酶（Tmm，将 DMS 氧化为二甲亚砜）是参与全球 DMS/DMSP 循环的最普遍的细菌基因。α变形菌（Pelagibacterales）和γ变形菌似乎在极地海洋的 DMS/DMSP 循环中发挥了重要作用。在极地海洋的宏基因组组装基因组（MAG）中也观察到多个 DMS/DMSP 循环基因同时存在于同一细菌基因组中的现象。极地海洋的微生物组合与水深显著相关，而与地理距离无关，这表明表面和深海之间的生境差异而不是扩散限制是塑造极地海洋中二甲基硫丙酸酯和二甲基硫循环相关微生物组合的关键因素。
总的来说，这项研究提供了北极和南极海洋中二甲基硫丙酸酯和二甲基硫循环中已知细菌基因的生物地理特征的全球概述，为进一步研究极地海洋微生物组中二甲基硫丙酸酯和二甲基硫循环在酶、代谢和过程水平上奠定了坚实的基础。
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