Niche Separation of Methanotrophic Archaea (ANME-1 and -2) in Methane-Seep Sediments of the Eastern Japan Sea Offshore Joetsu

Abstract

In this study, we investigated the diversity and spatial distribution of anaerobic methanotrophic archaea (ANMEs) in sediments of a gas hydrate field off Joetsu in the Japan Sea. Distribution of ANMEs in sediments was identified by targeting the gene for methyl coenzyme M reductase alpha subunit (mcrA), a phylogenetically conserved gene that occurs uniquely in methanotrophic and methanogenic archaea, in addition to 16S rRNA genes. Quantitative PCR analyses of mcrA genes in 14 piston core samples suggested that members of ANME-1 group would dominate AOM communities in sulfate-depleted sediments, even below the sulfate-methane interface, while ANME-2 archaea would prefer to populate in shallower sediments containing comparatively higher sulfate concentrations. These results suggest that, although the potential electron acceptors in sulfate-depleted habitats remain elusive, the niche separation of ANME-1 and -2 may be controlled by in situ concentration of sulfate and the availability in sediments.

Keywords:

• anaerobic oxidation of methane
• ANME archaea
• niche separation
• sulfate concentration
• methane hydrates
• Japan Sea

ACKNOWLEDGMENTS

We are grateful to all shipboard scientists and crews of the UT06 cruise for sample collection. We thank Takeshi Terada and Noriaki Masui for technical supports of molecular analyses. This work was supported by the Grant-in-Aid for Japan Society for the Promotion of Science (JSPS) Fellows (20-10764, to K.Y.) and in part by the Grant-in-Aid for Scientific Research: Project TAIGA (New Scientific Research on Innovative Areas, 20109003), the Grant-in-Aid from the Ministry of Education, Culture, Sports and Technology (MEXT), Japan (Nos. 19204049 and 16201002, to R.M.), and JAMSTEC Multidisciplinary Research Promotion Award (to F.I.).