A fearsome-looking predator appears to be lurking deep beneath the Earth's surface, a worm-like animal that feasts on victims roughly a kilometer down. Fortunately, it's only a half-millimeter long, and its victims are bacteria. Nevertheless, it's quite a surprise to find a multicellular organism that resides that deep, where sources of energy are very few and free oxygen is scarce.
This isn't the first surprise to come out of a deep mine in South Africa; when a group reported finding just a single bacterial species in samples taken at a depth of roughly 3km. Since then, evidence has accumulated that indicates that bacterial communities can form on the surfaces of cracks in the rock, living at high temperatures and in the midst of elevated salt concentrations that would kill many surface organisms.