Two miles underground

Bacteria don't make it onto the front page of the Chronicle that often - unless they are killing people. Friday's paper has news of the discovery of microbes existing two miles down in the fractured rock of a South African gold mine - a lightless pool of hot, pressurized salt water that stank of sulfur and noxious gases.

Using geologically produced hydrogen and sulfur for energy, such bacteria offer insights into the origin of life and the communities of bacteria that must have existed on the early earth before the atmosphere became oxygen rich. The newly discovered bacteria are distantly related to the Firmicutes division of microbes that exist near undersea hydrothermal vents.

Press reports followed a paper in Science last week.