Study On The Diversity Of Archaeal Retrieved From The Okhotsk Sea Gas Hydrate And Mud Wedge Sediments In The East China Sea Inner Shelf

To identify the distribution and diversity of archaea, methanotrophs and sulfate-reducing bacteria (SRB) in the gas hydrate bearing sediments of the Okhotsk Sea, we investigated the diversity of archaeal 16S rRNA, mcrA, dsrAB genes sequences by using a PCR-based cloning approach. Phylogenetic and statistic analysis of clone sequences showed that: The majority of archaeal phylotypes were Marine Benthic Group D (MBG-D), Marine Benthic Group B (MBG-B) and Marine Crenarchaeotic Group I (MG I). Additional few sequences fell into Anaerobic Methanotrophs 2c (ANME-2c), which was mainly detected from the surface layer of core LV39-25H. The archaeal communities of the surface layer of core LV39-40H significantly distinct from those of other six depth layers. mcrA gene clone libraries showed that the ANME population consisted predominantly of ANME-2 methane oxidizers (group c and d) at each studied layers; few ANME-1 community (group a) were found coexist with ANME-2 below the surface sediments of core LV39-40H. Few methanogens were mainly retrieved from 200cm layer of core LV39-25H and 180cm layer of core LV39-40H. Clones libraries of dsrAB gene displayed the diversified SRB community composition, especially in the surface layers of the two cores. Quite a number of dsrAB clones, recovered from all layers of the two cores, were affiliated with the DSS group (Desulfosarcina and Desulfococcus), which may form consortia with ANME archaea. Generally, the data analysed here show active anaerobic oxidation of methane in the Okhotsk Sea gas hydrate, and reveale the distribution and diversity of the involved microbe.Archaeal 16S rRNA gene clone libraries were constructed from different depth layers sediments to elucidate the distribution and diversity of archaea in the Zhejiang and Fujian coastal mud wedge of the inner continental shelf of the East China Sea. We obtained 473 useable clones and 50 different OTUs (Operational Taxonomic Units). Phylogenetic and statistic analysis of clone libraries showed that: archaeal 16S rRNA gene sequences were within phylums of Crenarchaeota and Euryarchaeota, respectively. The majority of archaeal phylotypes were Miscellaneous Crenarchaeotic Group (MCG), Additional few sequences fell into MBG-B, South African Gold Mine Euryarchaeotic Group (SAGMEG), ANME-3, MG-I and MBG-D. There might be anaerobic oxidation of methane carried out by group ANME-3 in this mud wedge. Homologous sequences analyses showed that the distribution of archaea in this mud wedge was related to the surrounding environment. UniFrac analysis and sediment environmental parameters indicated that the vertical distribution of archaea was intimately coincided with the variation of sediment total organic carbon content and grain size.Comparative analysis demonstrated that: Anaerobic Methanotrophs located at the gas hydrate bearing Oktostk Sea were mainly ANME-2 and few ANME-1, while the counterparts located at mud wedge sediments in the East China Sea were just few ANME-3. In the gas hydrate bearing Oktostk Sea, Crenarchaeota and Euryarchaeota each accouted for half of the total archaeal sequences. The majority of archaeal phylotypes were Marine Benthic Group D (MBG-D), Marine Benthic Group B (MBG-B) and Marine Crenarchaeotic Group I (MG-I). Archaeal sequence obtained from mud wedge sediments in the East China Sea mainly belonged to the phylum of Crenarchaeota (MCG). The type of sea areas and various environment factors, such as total organic carbon content, may be the explanation for the difference of archaral community.