title: Microbial community in black rust exposed to hot ridge flank crustal fluids.
abstract: During Integrated Ocean Drilling Program Expedition 301, we obtained a sample of black rust from a circulation obviation retrofit kit (CORK) observatory at a borehole on the eastern flank of Juan de Fuca Ridge. Due to overpressure, the CORK had failed to seal the borehole. Hot fluids from oceanic crust had discharged to the overlying bottom seawater and resulted in the formation of black rust analogous to a hydrothermal chimney deposit. Both culture-dependent and culture-independent analyses indicated that the black-rust-associated community differed from communities reported from other microbial habitats, including hydrothermal vents at seafloor spreading centers, while it shared phylotypes with communities previously detected in crustal fluids from the same borehole. The most frequently retrieved sequences of bacterial and archaeal 16S rRNA genes were related to the genera Ammonifex and Methanothermococcus, respectively. Most phylotypes, including phylotypes previously detected in crustal fluids, were isolated in pure culture, and their metabolic traits were determined. Quantification of the dissimilatory sulfite reductase (dsrAB) genes, together with stable sulfur isotopic and electron microscopic analyses, strongly suggested the prevalence of sulfate reduction, potentially by the Ammonifex group of bacteria. Stable carbon isotopic analyses suggested that the bulk of the microbial community was trophically reliant upon photosynthesis-derived organic matter. This report provides important insights into the phylogenetic, physiological, and trophic characteristics of subseafloor microbial ecosystems in warm ridge flank crusts.
authors.affiliation: Subground Animalcule Retrieval (SUGAR) Project, Extremobiosphere Research Center (XBR), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka 237-0061, Japan. nakagawas@jamstec.go.jp
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nakagawa
authors.forename: Fumio
authors.initials: F
authors.lastname: Inagaki
authors.forename: Yohey
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Bjørn Olav
authors.initials: BO
authors.lastname: Steinsbu
authors.forename: Mark Alexander
authors.initials: MA
authors.lastname: Lever
authors.forename: Ken
authors.initials: K
authors.lastname: Takai
authors.forename: Bert
authors.initials: B
authors.lastname: Engelen
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Sako
authors.forename: Charles Geoffrey
authors.initials: CG
authors.lastname: Wheat
authors.forename: Koki
authors.initials: K
authors.lastname: Horikoshi
mesh_terms: D001105:Archaea / Q000502:physiology*; D001419:Bacteria / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D044822:Biodiversity; D017753:Ecosystem; D019015:Geologic Sediments / Q000382:microbiology*; D008969:Molecular Sequence Data; D010140:Pacific Ocean; D012336:RNA, Ribosomal, 16S; D012111:Residence Characteristics; D014871:Water Microbiology
chemical_list: D012336:RNA, Ribosomal, 16S