Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/53733
標題: 臺灣西南海域甲烷水合物賦存區域微生物多樣化調查與甲烷古菌純化及甲烷生成潛力分析
Microbial Diversity, Methanogen Isolation and Methane Producing Potenals in Methane Hydrate Regions of Sw Offshore Taiwan
作者: 賴美津
關鍵字: 應用研究;Methane hydrate;海洋科學類;甲烷水合物;甲烷古菌;微生物生態結構;微生物多樣性;甲烷生成能力;Methanogen;Microbial community structure;Microbial diversity;Methane production.
摘要: 
甲烷水合物廣泛分佈於極區永凍層及陸緣海域等處。全球甲烷水合物的甲烷蘊藏量,保守估計至少有20 × 1015 立方公尺/一大氣壓,約為目前已知全球化石燃料等能源資源之有機碳總儲量的兩倍。相較於傳統的化石燃料,甲烷水合物是較為潔淨的能源,極可能成為二十一世紀最重要能源資源之一。目前一般認為甲烷的形成主要源自微生物作用或熱分解作用二種。由美國東南、北加州、祕魯、墨西哥灣等遠濱海域地區所採回甲烷水合物及含甲烷水合物的沉積物巖樣之烷氫類氣體組成及甲烷中碳同位素δ13C的分析結果顯示,絕大部分的甲烷水合物所含之甲烷係源自微生物作用。微生物中能生產甲烷氣體的僅有甲烷古菌(methanogen,甲烷菌,甲烷太古生物)。在大自然中,絕對厭氧的甲烷古菌能在任何無氧、低氧化還原電位的環境,利用簡單的H2+CO2, formate, acetate, methanol及methylamines作為主要碳源,進行甲烷化作用(methanogenesis)產生甲烷,提供能源和大氣中碳的循環並在生物的食物鏈中佔有相當基礎且重要的地位。產生甲烷氣體的甲烷化作用(methanogenesis)是甲烷古菌獨特且唯一獲得能量的特殊無氧呼吸方式。甲烷化作用相當複雜,反應所需的酵素系統、coenzyme及調控系統等所參與的基因佔其全部基因的25 % 左右。絕對厭氧的甲烷古菌能在任何無氧、低氧化還原電位的環境生長,對溫度、鹽度和水壓有相當高的極端適應性。目前已經純化的甲烷古菌中,能生長的溫度範圍由2-110 ℃,鹽濃度 0-4.5 M NaCl且能承受1- 600 atm或更高的水壓。 我們實驗室用來探討高鹽滲透逆境適應的嗜鹽甲烷古菌 (Methanohalophilus)能生長在1.2-4.3 M NaCl的環境,也自本土自然環境如彰化王功二林溪附近海域及養殖區、淡水河域、墾丁海域及車籠埔斷層地底取樣,純化甲烷古菌。 目前已純化約30株甲烷古菌,包含四株新種Methanofollis aquaemaris、Methanofollis formosanus、Methanocalculus taiwanensis及Methanocalculus chunghsingensis。甲烷水合物和甲烷古菌(Methanogen)的關係及甲烷水合物蘊藏區域的微生物生態結構在美國與日本等都有團隊進行探討。以16S rDNA基因的分析方式探討甲烷水合物沉積物附近微生物分佈發現微生物的種類相當多樣化,但太古生物(Archaea)的多樣性則相對侷限,主要以硫還原古菌、厭氧甲烷氧化古菌(AOM)與甲烷古菌為主。近一步分析顯示,甲烷水合物之間及上層,硫還原古菌與厭氧甲烷氧化古菌量較高,因此不少學者認為此類微生物族群架構可能影響甲烷水合物的穩定性。甲烷古菌則於甲烷水合物區域下方及附近的底泥占較高的比例。但不同樣區與不同方法的分析結果仍有些矛盾之處,因此甲烷自何處來仍有爭議。不過目前全球各樣區以16S rDNA或rRNA所分析的環境核酸樣品序列顯示,甲烷水合物區域的甲烷古菌多以利用H2+CO2為基質的 Methanomicrobiales與acetate為基質的Methanosarcinales為主。但是,這些研究大多尚未將微生物純化出來,目前唯一自甲烷水合物區域純化出的甲烷古菌是David R. Boone實驗室與日本科學家合作自日本Nankai trough取得的一株利用H2+CO2 和 formate為基質的中溫球菌Methanoculleus submarinus。台灣學界曾在臺灣西南海域發現有天然氣水合物廣泛分佈於南海大陸坡及南臺灣增積巖體中的證據。此研究目的是探討臺灣西南海域天然氣水合物沉積物的微生物生態結構與純化甲烷古菌,藉由我們實驗室的甲烷古菌純化技術純化此類特殊環境中的甲烷古菌,分析其特性以瞭解其特殊甲烷生合成與累積甲烷水合物的機制。另藉由16S rDNA基因轉殖定序與系統演化分析比對及即時定量PCR的應用,以分析甲烷水合物環境微生物的種類與量,進而構築其代謝關係以瞭解甲烷水合物微生物生態圈的功能。

Methane hydrates are an ice-like material in which methane molecules are trapped within cages of the crystalline lattice of water molecules. They are distributed along coastal margins, in the sediment of active and passive continental slope margins, as well as in terrestrial regions, trapping enormous volumes of methane, estimated at about twice the amount of all other known fossil fuel reserves. They have attracted much attention as an alternative energy resource potential, and may impact the global environment through generating slope instability.With most of the methane trapped in known hydrate formations being of biogenic origin, this represents a significant new source of natural gas from biological methanogenesis. Methanogenic archaea (Methanogen) are strict anaerobes that share a complex biochemistry for methane synthesis as part of their anaerobic respiration for energy metabolism. Genes involved in this unique methane producing process occupy more than 25% of coding genes of methanogen. Moreover, methanogens are the only Archaea that are truly cosmopolitan. Methanogenic species have been isolated from virtually every habitat in which anaerobic biodegradation of organic compounds occurs, moreover, isolates have also been obtained from geothermal springs, deep-sea vents and hypersaline environments. We have purified 30 strains of methanogens from Taiwan. Among them, four strains have been identified and characterized as new species and they are Methanofollis aquaemaris, Methanocalculus taiwanensis, Methanofollis formosanus and Methanocalculus chunghsingensis. Lately, we have isolated and characterized two novel methanogenic isolates from deep subsurface environment at the depth of 2000 m below land surface (mbls) of Chelungpu and San-Yi fault zones at Dai-Keng, Taichung. One is formate utilizing Methanobacterium palustre and the other is methanol utilizing Methanolobus sp..Microbial numbers are high in hydrate-bearing regions and metabolic studies of these sediments, based on incubations with stable isotopes of substrate and subsequent measurement of the isotope-containing product, have demonstrated methanogenesis, sulfate reduction, and methane oxidation. Phylogenetic analysis of DNA extracted from marine sediments in a methane hydrate zones have been investigated in Gulf of Mexico, Cascadia Margins, Nankai Trough and many elsewhere, which revealed similar but diverse results. In general, they all showed high diversity of bacteria and low diversity of Archaea. The sulfate reducers and anaerobic methane oxidization archaea often occur in the overlying and interior layers of hydrate. Methanogenic archaea including members of the orders Methanobacteriales and Methanosarcinales are often detected more abundantly at sediments below or nearby the hydrate. However, with tremendous environmental 16S DNA clone library, there is only one methanogen - Methanoculleus submarinus related with gas hydrate area has been isolated and characterized.The research team from Taiwan, supported by the Central Geological Survey (CGS) of the Ministry of Economic Affairs (MOEA), has been demonstrated lately that there are potential gas hydrate regions at SW offshore Taiwan. In this research proposal, we plan to investigate the microbial community structure of hydrate regions by phylogenetic analysis of 16S rDNA and mcr gene library. The microbial community analysis will provide the information of microbial ecological interaction to maintain the stability of the methane hydrate zones. In addition, we would like to enrich, isolate and character the methanogens from the hydrate area and use these isolates to study their methane producing capability and mechanism of hydrate formation.
URI: http://hdl.handle.net/11455/53733
其他識別: NSC97-2623-7005-008-ET
Appears in Collections:生命科學系所

Show full item record
 

Google ScholarTM

Check


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.