HR: 1340h
AN: T33A-0523    [Abstracts]
TI: Unique Thermophiles Supported by the Ocean Crustal Fluids Exiting From a Borehole in the Eastern Flank of Juan de Fuca Ridge.
AU: * Nakagawa, S
EM: nakagawas@jamstec.go.jp
AF: Subground Animalcule Retrieval (SUGAR) Program, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, 237-0061 Japan
AU: Inagaki, F
EM: inagaki@jamstec.go.jp
AF: Subground Animalcule Retrieval (SUGAR) Program, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, 237-0061 Japan
AU: Suzuki, Y
EM: yohey@jamstec.go.jp
AF: Subground Animalcule Retrieval (SUGAR) Program, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, 237-0061 Japan
AU: Takai, K
EM: kent@jamstec.go.jp
AF: Subground Animalcule Retrieval (SUGAR) Program, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, 237-0061 Japan
AU: Horikoshi, K
EM: horikok@jamstec.go.jp
AF: Subground Animalcule Retrieval (SUGAR) Program, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, 237-0061 Japan
AB: Very little is known about the potential of ocean crustal fluids on ridge flanks to sustain microbial ecosystem. An unprecedented chance to investigate the occurrence of microbes within the crustal fluids is given by a borehole observatory, CORK (Circulation Obviation Retrofit Kit). The CORK consists of two parts: instruments installed in the sealed part of the cased borehole drilled by the Ocean Drilling Program (ODP), and a data logger and fluids sampling port sitting on the seafloor. Recently, a study using the CORK suggested the presence of unique microorganisms in ~64 deg C of crustal fluids emanated from a 295-meter-deep borehole in the eastern flank of Juan de Fuca Ridge (35 Ma crust) (Cowen et al., 2003, Science, 299, 120-123). Most of the 16S rRNA gene detected in the fluids related to sulfate-reducing genera (Desulfotomaculum, Ammonifex, and Desulfonatronovibrio), implying that fluids circulating within aging ocean crust potentially support microbial sulfate-reduction. When we recovered the CORK during the Juan de Fuca cruise of Integrated Ocean Drilling Program (IODP), sulfide deposits attached to the CORK body was found. The microbial community in the sulfide deposits inferred by clone sequencing of environmental 16S rRNA genes was distinct from those hitherto reported in other microbial habitats including natural deep-sea vents on ridge crests and subduction zones, but similar in part with that reported in the fluids emanated from the same CORK. Most frequently retrieved clones of bacterial and archaeal 16S rRNA gene were related to Ammonifex and Methanococcales, respectively. Semi-quantitative cultivation experiments revealed that over 103 cells per cm3 of the sulfide deposits were culturable. Surprisingly, none of the microbes widely distributing in natural deep-sea hydrothermal environments, i.e. Thermococcales, Aquificales, and epsilon-Proteobacteria, could be detected or cultured. Culturable microbial community consisted mainly of Methanothermococcus sp., members of the hydrogenotrophic and thermophilic methanogen, and which also included diverse thermophilic fermenters and thermophilic sulfate reducers belonging to the previously uncultivated phylogroups. Detection of dissimilatory sulfite reductase (dsrAB) genes, together with the SEM-EDX analysis, confirmed the occurrence of microbial sulfate-reduction. Stable carbon isotopic analysis indicated the microbial community mainly depended on photosynthesis-derived organic matter. Our study demonstrated that the occurrence of diverse, unique, and active thermophiles supported by fluids emanated from the deep basaltic crust, which is probably driven by dissolved nutrients in the hydrothermal fluids.
DE: 0448 Geomicrobiology
DE: 0450 Hydrothermal systems (1034, 3017, 3616, 4832, 8135, 8424)
DE: 0465 Microbiology: ecology, physiology and genomics (4840)
SC: Tectonophysics [T]
MN: Fall Meeting 2005