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Images: Is Life Thriving Deep Beneath the Seafloor?

In 1991, scientists aboard the submersible Alvin witnessed the aftermath of a very recent volcanic seafloor eruption and found themselves in a virtual blizzard of white debris.

Examining the white flocs discharged from the 1991 seafloor eruption, WHOI scientists discovered a new genus of bacteria called Arcobacter. (Craig Taylor & Carl Wirsen, WHOI.)

A titanium ring deployed at a Pacific hydrothermal vent site indicates the presence of bacteria thriving beneath the seafloor. Within days, Arcobacter bacteria, discharging from the subsurface, rapidly colonize the ring, producing a white sulfur filament mat up to 3 centimeters thick as they grow. (Craig Taylor and Carl Wirsen, WHOI and Françoise Gaill, Université Pierre et Marie Curie, Paris, France.)

World?s largest bacterium?In 1999 scientists discovered a previously unknown bacterium, which is large enough to be seen with the naked eye. Found off the coast of Namibia, the bacteria grow in long lines of single cells, each stuffed with reflective white globules of sulfur. The bacteria resembled a string of pearls to its discoverers, who named it Thiomargarita namibienus (?Sulfur pearl of Namibia?). The bacteria have evolved to live on seafloor sediments, where they find hydrogen sulfide for energy and nitrate for respiration. Their size is due to a large vacuole that fills the interior of their cells like inflated balloons. The vacuole stores nitrate, giving Thiomargarita the ability to survive periods when oxygen is lacking?a built-in equivalent of an oxygen-storing SCUBA tank that allows humans to remain alive underwater.