Wei Xiao-Meng, He Ruo, Chen Min, Su Yao, Ma Ruo-Chan
Department of Environmental Engineering, Zhejiang University, Hangzhou, 310058, China.
Environ Sci Pollut Res Int. 2016 Apr;23(8):7517-28. doi: 10.1007/s11356-015-6017-y. Epub 2016 Jan 5.
Methanotrophs not only play an important role in mitigating CH4 emissions from the environment, but also provide a large quantity of CH4-derived carbon to their habitats. In this study, the distribution of CH4-derived carbon and microbial community was investigated in a consortium enriched at three O2 tensions, i.e., the initial O2 concentrations of 2.5 % (LO-2), 5 % (LO-1), and 21 % (v/v) (HO). The results showed that compared with the O2-limiting environments (2.5 and 5 %), more CH4-derived carbon was converted into CO2 and biomass under the O2 sufficient condition (21 %). Besides biomass and CO2, a high conversion efficiency of CH4-derived carbon to dissolved organic carbon was detected in the cultures, especially in LO-2. Quantitative PCR and Miseq sequencing both showed that the abundance of methanotroph increased with the increasing O2 concentrations. Type II methanotroph Methylocystis dominated in the enrichment cultures, accounting for 54.8, 48.1, and 36.9 % of the total bacterial 16S rRNA gene sequencing reads in HO, LO-1, and LO-2, respectively. Methylotrophs, mainly including Methylophilus, Methylovorus, Hyphomicrobium, and Methylobacillus, were also abundant in the cultures. Compared with the O2 sufficient condition (21 %), higher microbial biodiversity (i.e., higher Simpson and lower Shannon indexes) was detected in LO-2 enriched at the initial O2 concentration of 2.5 %. These findings indicated that compared with the O2 sufficient condition, more CH4-derived carbon was exuded into the environments and promoted the growth of non-methanotrophic microbes in O2-limiting environments.
甲烷氧化菌不仅在减少环境中甲烷排放方面发挥着重要作用，还为其栖息地提供大量源自甲烷的碳。在本研究中，对在三种氧气张力下富集的一个聚生体中源自甲烷的碳和微生物群落的分布进行了研究，即初始氧气浓度分别为2.5%（低氧-2）、5%（低氧-1）和21%（体积/体积）（高氧）。结果表明，与氧气受限环境（2.5%和5%）相比，在氧气充足条件（21%）下，更多源自甲烷的碳被转化为二氧化碳和生物量。除了生物量和二氧化碳外，在培养物中还检测到源自甲烷的碳向溶解有机碳的高转化效率，尤其是在低氧-2中。定量PCR和Miseq测序均表明，甲烷氧化菌的丰度随氧气浓度的增加而增加。II型甲烷氧化菌甲基孢囊菌在富集培养物中占主导地位，分别占高氧、低氧-1和低氧-2中细菌16S rRNA基因测序总读数的54.8%、48.1%和36.9%。甲基营养菌在培养物中也很丰富，主要包括嗜甲基菌属、食甲基菌属、生丝微菌属和甲基芽孢杆菌属。与氧气充足条件（21%）相比，在初始氧气浓度为2.5%的低氧-2中检测到更高的微生物多样性（即更高的辛普森指数和更低的香农指数）。这些发现表明，与氧气充足条件相比，在氧气受限环境中，更多源自甲烷的碳被释放到环境中，并促进了非甲烷氧化微生物的生长。
