First Investigation of the Microbiology of the Deepest Layer of Ocean Crust

PLoS One

Olivia U. Mason¹  Martin R. Fisk¹  Jizhong Zhou²  Joy D. Van Nostrand²  Tatsunori Nakagawa³  Stephen J. Giovannoni⁴  Martin Rosner⁵  Akihiko Maruyama⁶ 

[1] College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, United States of America;Department of Botany and Microbiology, Institute for Environmental Genomics, University of Oklahoma, Norman, Oklahoma, United States of America;Department of Earth Sciences, Tohoku University, Miyagi, Japan;Department of Microbiology, Oregon State University, Corvallis, Oregon, United States of America;Petrology of the Oceanic Crust, Universität Bremen, Bremen, Germany;Research Institute of Biological Resources, National Institute of Advanced Industrial Science and Technology, Ibaraki, Japan

关键词: Hydrocarbons;    Cloning;    Oceans;    Oceanic crust;    Carbonates;    Methane;    Sea water;    Denaturing gradient gel electrophoresis;   

DOI  :  10.1371/journal.pone.0015399

学科分类：医学（综合）

来源: Public Library of Science

【 摘 要 】

The gabbroic layer comprises the majority of ocean crust. Opportunities to sample this expansive crustal environment are rare because of the technological demands of deep ocean drilling; thus, gabbroic microbial communities have not yet been studied. During the Integrated Ocean Drilling Program Expeditions 304 and 305, igneous rock samples were collected from 0.45-1391.01 meters below seafloor at Hole 1309D, located on the Atlantis Massif (30 °N, 42 °W). Microbial diversity in the rocks was analyzed by denaturing gradient gel electrophoresis and sequencing (Expedition 304), and terminal restriction fragment length polymorphism, cloning and sequencing, and functional gene microarray analysis (Expedition 305). The gabbroic microbial community was relatively depauperate, consisting of a low diversity of proteobacterial lineages closely related to Bacteria from hydrocarbon-dominated environments and to known hydrocarbon degraders, and there was little evidence of Archaea. Functional gene diversity in the gabbroic samples was analyzed with a microarray for metabolic genes (“GeoChip”), producing further evidence of genomic potential for hydrocarbon degradation - genes for aerobic methane and toluene oxidation. Genes coding for anaerobic respirations, such as nitrate reduction, sulfate reduction, and metal reduction, as well as genes for carbon fixation, nitrogen fixation, and ammonium-oxidation, were also present. Our results suggest that the gabbroic layer hosts a microbial community that can degrade hydrocarbons and fix carbon and nitrogen, and has the potential to employ a diversity of non-oxygen electron acceptors. This rare glimpse of the gabbroic ecosystem provides further support for the recent finding of hydrocarbons in deep ocean gabbro from Hole 1309D. It has been hypothesized that these hydrocarbons might originate abiotically from serpentinization reactions that are occurring deep in the Earth's crust, raising the possibility that the lithic microbial community reported here might utilize carbon sources produced independently of the surface biosphere.

【 授权许可】

CC BY