A Constant Flux of Diverse Thermophilic Bacteria into the Cold Arctic Seabed

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Science  18 Sep 2009:
Vol. 325, Issue 5947, pp. 1541-1544
DOI: 10.1126/science.1174012

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Microorganisms have been repeatedly discovered in environments that do not support their metabolic activity. Identifying and quantifying these misplaced organisms can reveal dispersal mechanisms that shape natural microbial diversity. Using endospore germination experiments, we estimated a stable supply of thermophilic bacteria into permanently cold Arctic marine sediment at a rate exceeding 108 spores per square meter per year. These metabolically and phylogenetically diverse Firmicutes show no detectable activity at cold in situ temperatures but rapidly mineralize organic matter by hydrolysis, fermentation, and sulfate reduction upon induction at 50°C. The closest relatives to these bacteria come from warm subsurface petroleum reservoir and ocean crust ecosystems, suggesting that seabed fluid flow from these environments is delivering thermophiles to the cold ocean. These transport pathways may broadly influence microbial community composition in the marine environment.

  • Present address: Department of Geology and Geochemistry, Stockholm University, Svante Arrhenius Väg 8C, 106 91 Stockholm, Sweden.

  • Present address: Institute of Biology, University of Southern Denmark, Campusvej 55, 5320 Odense M Denmark.

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