Title Metagenomic analysis reveals the contribution of anaerobic methanotroph-1b in the oxidation of methane at the Ulleung Basin, East Sea of Korea
Author Jin-Woo Lee1,2, Kae Kyoung Kwon1, Jang-Jun Bahk3, Dong-Hun Lee2, Hyun Sook Lee1, Sung Gyun Kang1, and Jung-Hyun Lee1*
Address 1Marine Biotechnology Research Division, Korea Institute of Ocean Science and Technology, Ansan 15627, Republic of Korea, 2Department of Microbiology, Chungbuk National University, Cheongju 28644, Republic of Korea, 3Petroleum and Marine Resources Research Division, Korea Institute of Geoscience and Mineral Resources, Daejeon 34132, Republic of Korea
Bibliography Journal of Microbiology, 54(12),814-822, 2016,
DOI 10.1007/s12275-016-6379-y
Key Words sulfate methane transition zone (SMTZ), anaerobic methanotroph-1b (ANME-1b), reverse methanogenesis pathway, metagenomics
Abstract We have previously identified a sulfate methane transition zone (SMTZ) within the methane hydrate-bearing sediment in the Ulleung Basin, East Sea of Korea, and the presence of ANME-1b group in the sediment has been shown by phylogenetic analysis of a 16S rRNA gene. Herein, we describe taxonomic and functional profiling in the SMTZ sample by metagenomic analysis, comparing with that of surface sediment. Metagenomic sequences of 115 Mbp and 252 Mbp were obtained from SMTZ and surface sediments, respectively. The taxonomic profiling using BLASTX against the SEED within MG-RAST showed the prevalence of methanogens (19.1%), such as Methanosarcinales (12.0%) and Methanomicrobiales (4.1%) predominated within the SMTZ metagenome. A number of 185,200 SMTZ reads (38.9%) and 438,484 surface reads (62.5%) were assigned to functional categories, and methanogenesis-related reads were statistically significantly overrepresented in the SMTZ metagenome. However, the mapping analysis of metagenome reads to the reference genomes, most of the sequences of the SMTZ metagenome were mapped to ANME-1 draft genomes, rather than those of methanogens. Furthermore, the two copies of the methyl-coenzyme M reductase gene (mcrA) segments of the SMTZ metagenome were clustered with ANME-1b in the phylogenetic cluster. These results indicate that ANME- 1b reads were miss-annotated to methanogens due to limitation of database. Many of key genes necessary for reverse methanogenesis were present in the SMTZ metagenome, except for N5,N10-methenyl-H4MPT reductase (mer) and CoBCoM heterodisulfide reductase subunits D and E (hdrDE). These data suggest that the ANME-1b represents the primary player the anaerobic methane oxidation in the SMTZ, of the methane hydrate-bearing sediment at the Ulleung Basin, East Sea of Korea.