The goal of our investigations is to understand the role of crustal fluids as a driving force for the marine deep-biosphere. To analyze microbial activities and community structures, contamination-free sediment samples were recovered during IODP Leg 301 to the Juan de Fuca Ridge off the coast of Oregon.
The sediment of IODP Site 1301 (water depth: 2665 m, sediment thickness: 265 m) is characterized by a diffusive flow of fluids from the underlying oceanic crust, a steep temperature gradient of 0.23 °C/m, and two sulfate-methane transition zones.
The hypothesis that this geochemical regime of an "upside down" electron acceptor series fuels the deep biosphere was proven by activity measurements and the quantification of cells along the sediment column. Total cell counts and the number of 16S rRNA genes increased within the sulfate-methane transition zones and above the basement. Potential phosphatase activity was enhanced in phosphate-depleted layers towards the sediment-basement interface. Rates of sulfate reduction and anaerobic oxidation of methane (AOM) were elevated within the lower sulfate-methane transition zone.
Further investigations focused on isolating indigenous microorganisms. Microbial growth was stimulated in various enrichment cultures from the entire sediment column. Molecular screening via PCR-DGGE, used to determine the microbial composition of enrichments, revealed a broad set of different phylotypes. These data allow a guided isolation of unique deep-biosphere microorganisms. A subsequent characterization will determine special adaptations to their habitat.
Official IODP Leg 301 webpage
Reisebericht von Bert Engelen Cruise report (in German)
Teacher at Sea (Detailed cruise report)
Fichtel K, Mathes F, Könneke M, Cypionka H, Engelen B (2012) Isolation of sulfate-reducing bacteria from sediments above the deep-subseafloor aquifer. Front Microbio 3:65
Engelen B and Cypionka H (2008) The subsurface of tidal flats as a model for the deep biosphere. Ocean Dynamics 59:385–391
Engelen B, Ziegelmüller K, Wolf L, Köpke B, Gittel A, Treude T, Nakagawa S, Inagaki F, Lever MA, Steinsbu BO, Cypionka H (2008) Fluids from the oceanic crust support microbial activities within the deep biosphere. Geomicrobiology J 25:56-66
Ziegelmüller K, Könneke M, Cypionka H, and Engelen B (2007) Cultivation of sulfate-reducing bacteria from deep sediment layers that are influenced by crustal fluids (IODP Leg 301)
Extended abstract, IODP/ICDP-Kolloquium Potsdam
Ziegelmüller K, Cypionka H, and Engelen B (2007) Hydrothermal fluids from the oceanic crust stimulate metabolic activities of deep-biosphere populations (IODP Leg 301). Extended abstract, IODP/ICDP-Kolloquium Potsdam
Lever MA, Alperin M, Engelen B, Inagaki F, Nakagawa S, Steinsbu BO, Teske A, IODP Expedition 301 Scientists (2006) Trends in basalt and sediment core contamination during IODP expedition 301. Geomicrobiol J 23:517-530
Nakagawa S, Inagaki F, Suzuki Y, Steinsbu BO, Lever MA, Takai K, Engelen B, Sako Y, Wheat CG, Horikoshi K, and IODP Exp. 301 Scientists (2006) Microbial Community in Black Rust Exposed to Hot Ridge Flank Crustal Fluids. Appl Environ Microbiol 72:6789–6799