Defining boundaries for the distribution of microbial communities beneath the sediment-buried, hydrothermally active seafloor

authored by

Katsunori Yanagawa, Akira Ijiri, Anja Breuker, Sanae Sakai, Youko Miyoshi, Shinsuke Kawagucci, Takuroh Noguchi, Miho Hirai, Axel Schippers, Jun Ichiro Ishibashi, Yoshihiro Takaki, Michinari Sunamura, Tetsuro Urabe, Takuro Nunoura, Ken Takai

Abstract

Subseafloor microbes beneath active hydrothermal vents are thought to live near the upper temperature limit for life on Earth. We drilled and cored the Iheya North hydrothermal field in the Mid-Okinawa Trough, and examined the phylogenetic compositions and the products of metabolic functions of sub-vent microbial communities. We detected microbial cells, metabolic activities and molecular signatures only in the shallow sediments down to 15.8 m below the seafloor at a moderately distant drilling site from the active hydrothermal vents (450 m). At the drilling site, the profiles of methane and sulfate concentrations and the δ 13 C and δD isotopic compositions of methane suggested the laterally flowing hydrothermal fluids and the in situ microbial anaerobic methane oxidation. In situ measurements during the drilling constrain the current bottom temperature of the microbially habitable zone to ∼45 °C. However, in the past, higher temperatures of 106-198 °C were possible at the depth, as estimated from geochemical thermometry on hydrothermally altered clay minerals. The 16S rRNA gene phylotypes found in the deepest habitable zone are related to those of thermophiles, although sequences typical of known hyperthermophilic microbes were absent from the entire core. Overall our results shed new light on the distribution and composition of the boundary microbial community close to the high-temperature limit for habitability in the subseafloor environment of a hydrothermal field.

Organisation(s)

Institute of Microbiology

External Organisation(s)

Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
University of Tokyo
Kyushu University
Federal Institute for Geosciences and Natural Resources (BGR)
Kochi University

Type

Article

Journal

ISME Journal

Volume

11

Pages

529-542

No. of pages

14

ISSN

1751-7362

Publication date

18.10.2016

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Microbiology, Ecology, Evolution, Behavior and Systematics

Electronic version(s)

https://doi.org/10.1038/ismej.2016.119 (Access: Closed)