南海Formosa冷泉区沉积物微生物多样性与分布规律研究

Diversity and distribution of microorganisms in the sediment of Formosa cold seep in South China Sea

【目的】当前对全球冷泉生态系统微生物生态学研究显示,冷泉生态系统中主要微生物类群为参与甲烷代谢的微生物,它们的分布差异与所处冷泉区生物地球化学环境密切相关。但在冷泉区内也存在环境因子截然不同的生境,尚缺乏比较冷泉区内小尺度生境间微生物多样性和分布规律的研究。本研究旨在分析南海Formosa冷泉区内不同生境间微生物多样性差异,完善和理解不同环境因子对冷泉内微生物群落结构的影响。【方法】对采集自南海Formosa冷泉区不同生境(黑色菌席区、白色菌席区和碳酸盐岩区)沉积物样本中古菌和细菌16S rRNA基因进行测序,结合环境因子,比较微生物多样性差异,分析环境因子对微生物分布的影响。【结果】发现在Formosa冷泉内的不同生境中,甲烷厌氧氧化古菌(anaerobic methanotrophic archaea,ANME)是主要古菌类群,占古菌总体相对丰度超过70%;在菌席区ANME-1b和ANME-2a/b是主要ANME亚群,碳酸盐岩区则是ANME-1b。硫酸盐还原菌(sulfate-reducing bacteria,SRB)和硫氧化菌(sulfur-oxidizing bacteria,SOB)是冷泉各生境内细菌的最主要类群,二者均占细菌总体相对丰度的20%以上,其中Desulfosarcinaceae占SRB的50%以上,Sulfurovaceae和Sulfurimonadaceae共占SOB的90%以上;其他占细菌类群超过10%的还有Gammaproteobacteria和Chloroflexi。通过对甲烷代谢保守功能基因mcrA(methyl coenzyme-M reductase alpha subunit)、硫酸盐还原保守基因dsrA(dissimilatory sulfite reductase alpha subunit)的定量PCR结果发现mcr A基因拷贝数为109–1010 copies/g(湿重),dsrA基因拷贝数为108–109 copies/g(湿重),均高于非冷泉对照区沉积物1–2个数量级。群落分析结果显示冷泉区不同生境间的群落结构存在显著差异,且多因素分析的结果显示不同生境中微生物多样性和分布与甲烷、硫化氢、硫酸盐以及溶解性无机碳(dissolved inorganic carbon,DIC)浓度显著相关。【结论】本研究通过对冷泉区内菌席区和碳酸盐岩区异质性生境的微生物多样性进行分析,发现主要的微生物类群均为参与甲烷(厌氧甲烷氧化)和硫(硫酸盐还原、硫氧化)代谢的微生物,但不同生境中微生物多样性和分布差异明显,主要受控于甲烷、硫酸盐、硫化氢和DIC等环境因子。

[Objective] Global survey on microbial diversity of cold seep ecosystem pointed out that cold seeps had developed specific types of microorganisms,the main groups were microorganisms involved in methane metabolism,and their distribution were closely linked to the biogeochemical characteristics of the certain cold seep.However,different environmental conditions and small-scale habitats may present inside the cold seep,and studies comparing the microbial diversity and distribution between small-scale habitats in cold seep were lacking.The purpose of this study was to analyze the differences in microbial diversity among different habitats in the Formosa cold seep of South China Sea,and to improve and understand the impact of different environmental factors on the microbial community structure inside cold seep.[Methods] Sediment samples were collected from different habitats including microbial mat area and carbonate rock area from the Formosa cold seep of South China Sea.16S rRNA genes of archaea and bacteria were sequenced and analyzed.Combined with environmental factors,we compared differences in microbial diversity,and analyzed the impact of environment factors on microbial distribution.[Results] We found that in different habitats in the Formosa cold seep,anaerobic methanotrophic archaea(ANME) was the major archaeal group,accounting for more than 70% of the total relative abundance of archaea;ANME-1b and ANME-2a/b became the main ANME subgroups in microbial mat area,ANME-1b was dominant in the carbonate rock area.Sulfate-reducing bacteria(SRB) and sulfur-oxidizing bacteria(SOB) were the main groups of bacteria in each habitat of cold seep,and they both accounted for more than 20% of the total relative abundance of bacteria.Among them,Desulfosarcinaceae accounted for more than 50% of the SRB,and Sulfurovaceae and Sulfurimonadaceae together accounted for more than 90% of the SOB;other taxa accounting for more than 10% of the bacteria were Gammaproteobacteria and Chloroflexi.The quantitative PCR results of the conserved methane metabolism gene mcrA(methyl coenzyme-M reductase alpha subunit) and the sulfate reduction conserved gene dsrA(dissimilatory sulfite reductase alpha subunit) showed that the copy number of mcrA gene was 109–1010 copies/g(wet weight),and the copy number of dsrA gene was 108–109 copies/g(wet weight),which were 10–100 times higher than those of the control area located outside the cold seep.The results of community analysis showed that there were significant differences in community structure among different habitats,and the results of multivariate analysis showed that the diversity and distribution of microorganisms in different habitats were significantly associated with the concentration of methane,hydrogen sulfide,sulfate,and dissolved inorganic carbon(DIC).[Conclusion] This research analyzed the microbial diversity of the heterogenous habitats including the microbial mat area and the carbonate rock area in the Formosa cold seep.We found that the main microbial groups were involved in methane(anaerobic methane oxidation) and sulfur(sulfate reduction,sulfur oxidation) metabolism cycle,however,the diversity and distribution of microorganisms in different habitats were significantly different,mainly controlled by environmental factors such as methane,sulfate,hydrogen sulfide and DIC.