Division of Biological Engineering, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology Cambridge, MA, USA ; Center for Microbial Oceanography: Research and Education (C-MORE), University of Hawaii Honolulu, HI, USA.
Front Microbiol. 2013 Nov 26;4:340. doi: 10.3389/fmicb.2013.00340. eCollection 2013.
Aerobic degradation of methylphosphonate (MPn) by marine bacterioplankton has been hypothesized to contribute significantly to the ocean's methane supersaturation, yet little is known about MPn utilization by marine microbes. To identify the microbial taxa and metabolic functions associated with MPn-driven methane production we performed parallel metagenomic, metatranscriptomic, and functional screening of microcosm perturbation experiments using surface water collected in the North Pacific Subtropical Gyre. In nutrient amended microcosms containing MPn, a substrate-driven microbial succession occurred. Initially, the addition of glucose and nitrate resulted in a bloom of Vibrionales and a transcriptional profile dominated by glucose-specific PTS transport and polyhydroxyalkanoate biosynthesis. Transcripts associated with phosphorus (P) acquisition were also overrepresented and suggested that the addition of glucose and nitrate had driven the community to P depletion. At this point, a second community shift occurred characterized by the increase in C-P lyase containing microbes of the Vibrionales and Rhodobacterales orders. Transcripts associated with C-P lyase components were among the most highly expressed at the community level, and only C-P lyase clusters were recovered in a functional screen for MPn utilization, consistent with this pathway being responsible for the majority, if not all, of the methane accumulation we observed. Our results identify specific bacterioplankton taxa that can utilize MPn aerobically under conditions of P limitation using the C-P lyase pathway, and thereby elicit a significant increase in the dissolved methane concentration.
海洋细菌浮游生物对甲基膦酸盐（MPn）的需氧降解，据推测对海洋甲烷过饱和有重大贡献，但对于海洋微生物对 MPn 的利用却知之甚少。为了确定与 MPn 驱动的甲烷产生相关的微生物类群和代谢功能，我们对北太平洋亚热带环流中采集的表层水进行了平行的宏基因组、宏转录组和功能筛选微宇宙扰动实验。在含有 MPn 的营养物添加微宇宙中，发生了底物驱动的微生物演替。最初，添加葡萄糖和硝酸盐导致 Vibrionales 的大量繁殖和以葡萄糖特异性 PTS 转运和聚羟基烷酸生物合成为主导的转录谱。与磷（P）获取相关的转录本也过表达，表明添加葡萄糖和硝酸盐已导致群落中 P 耗尽。此时，发生了第二次群落转变，以 Vibrionales 和 Rhodobacterales 目中含有 C-P 裂合酶的微生物增加为特征。与 C-P 裂合酶成分相关的转录本在群落水平上表达最高，并且在 MPn 利用的功能筛选中仅回收了 C-P 裂合酶簇，这与该途径负责我们观察到的大部分（如果不是全部）甲烷积累一致。我们的研究结果确定了在 P 限制条件下，能够通过 C-P 裂合酶途径有氧利用 MPn 的特定浮游细菌类群，从而使溶解甲烷浓度显著增加。
