Study On The Microbial Diversity In Terrestrial Gas Hydrate Habitat And Novel Species Taxonomy

Gas hydrate is a potential future energy resource.Due to its little burning pollution,high energy density and abundant resource,gas hydrate has been studied widly.Since gas hydrate was drilled in Qilian Mountain permafrost,Qinghai Province,in 2009,China had become one of countries possessing rich gas hydrate.Currently,great achievements have been made in resources investigation of terrestrial gas hydrate.However,gas hydrate prospecting is restricted for complex factors of gas hydrate formation and inadequate understanding of accumulation mechanism and distribution rule.In this study,subsurface microbial diversity in Sanlutian of Muli basin,Qilian Mountains was the key concern.Combined with subsurface microbial diversity in Mohe basin and Qiangtang basin,characteristics of microbial community in terrestrial gas hydrate habitat was summarized based on analysis of microbial community structure,microbial community distribution,interacting relationship between genera,microbial community function and relationships between microorganisms and gas hydrate.The study of characteristics of microbial community was aimed at providing foundation for the research of formation mechanism,distribution rule and defined area of gas hydrate and environmental monitoring during gas hydrate exploitation.Meanwhile,polyphasic taxonomic approach was used to identify new bacterial isolates got from subsurface microbial species resource of Muli basin,Mohe basin and Qiangtang basin,and novel taxa would further the understanding of microbial species in terrestrial gas hydrate habitat and pave the way for exploiting microbial species resource in terrestrial gas hydrate habitat.The conclusions were shown as follows:1.In terrestrial gas hydrate habitat,the abundance of Bacteria was high as well as in ordinary soil.Taxa of Bacteria were rich and could be classified to 23 phyla and 645 genera.Characteristic genera in this habitat are Pseudomonas and Sphingomonas,and the two genera were mutually exclusive.In respects of function,microbes as a whole tended to degrade organic matter,which consistented with the rich organic matter in this habitat.Methanogens,ANME-2d(anaerobic methanotrophs),Methylosinus(aerobic methanotrophs)and SRB with unvolved in anaerobic methane oxidation were found in this habitat.Vertical distribution of bacterial and archaeal communities,methanogens,methanotrophs and Sulfate Reducing Bacteria(SRB)had little relation with that of hydrate.But,horizontal distributions of methanogens,methanotrophs and SRB were related to that of gas hydrate,specially to speculated area of gas hydrate.2.Novel isolate DK6-37T got from subsurface microbial species resource of Muli basin was identified to be a novel species of Hymenobacter gen.,which was named Hymenobacter qilianensis sp.nov..The brief features of it were as follows:The novel species was a red-pink,Gram-negative,rod-shaped,non-motile,non-spore-forming bacterium.Optimum growth was observed at 28?,pH 7.0 and 0%NaCl.The novel species was found to contain MK-7 as the predominant menaquinone.The polar lipids were identified as phosphatidylethanolanmine,two unknown aminophospholipids,one unknown aminolipid and three unknown polar lipids.The major fatty acids were identified as summed feature 3(C16:1?7c and/or C16:1?6c),summed feature 4(anteiso-C17:1B and/or iso-C17:1I),C16:1?5c,iso-C17:03-OH,iso-C15:0 and C18:0.The DNA G+C content was determined to be 67.4 mol%.3.Novel isolate Z8T got from subsurface microbial species resource of Mohe basin was identified to be a novel genus and novel species of Phyllobacteriaceae fam.,which was designated as Tianweitania sediminis gen.nov.,sp.nov..The brief features of it ware as follows:The major cellular fatty acids were summed feature 4(iso-C17:1I and/or anteiso-C17:1 B)and summed feature 8(C18:1?7 c and/or C18:1?6c).The major respiratory quinone was ubiquinone-10.The three major polar lipids of strain Z8T consist of glycolipids,phosphatidylethanolamine and phosphatidylmethlethaolamine.The DNA G+C content was 59.6 mol%.4.Novel isolate Z6T got from subsurface microbial species resource of Mohe basin was identified to be a novel species of Sphingomonas gen.,which was designated as Sphingomonas mohensis sp.nov..The brief features of it were as follows:The novel species was a gram-reaction-negative,rod-shaped bacterium.Optimum growth occurs at 30?,pH 7.0 and 0%NaCl.The polar lipid profile were identified as diphosphatidylglycerol,phosphatidylethanolamine and sphingoglycolipid,two unidentified phospholipids and the major quinone was Q-10.The major fatty acids were summed feature 8(C18:1?7c and/or C18:1?6c)and summed feature 3(C16:1?6c and/or C16:1?7c).The predominant polyamine was homospermidine.The DNA G+C content of strain Z6T is 65.2 mol%.