Scientists from Woods Hole Oceanographic Institution (WHOI) reveal how microorganisms could survive in rocks nestled thousands of feet beneath the ocean floor in the lower oceanic crust, in a study published on March 11 in Nature.
The first analysis of messenger RNA—genetic material containing instructions for making different proteins—from this remote region of Earth, coupled with measurements of enzyme activities, microscopy, cultures, and biomarker analyses provides evidence of a low biomass, but diverse community of microbes that includes heterotrophs that obtain their carbon from other living (or dead) organisms.
“Organisms eking out an existence far beneath the seafloor live in a hostile environment,” says Dr. Paraskevi (Vivian) Mara, a WHOI biochemist and one of the lead authors of the paper. Scarce resources find their way into the seabed through seawater and subsurface fluids that circulate through fractures in the rock and carry inorganic and organic compounds.
To see what kinds of microbes live at these extremes and what they do to survive, researchers collected rock samples from the lower oceanic crust over three months aboard the International Ocean Discovery Program Expedition 360. The research vessel traveled to an underwater ridge called Atlantis Bank that cuts across the Southern Indian Ocean. There, tectonic activity exposes the lower oceanic crust at the seafloor, “providing convenient access to an otherwise largely inaccessible realm,” write the authors.
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