If the rest of the world is like the Peruvian Margin, then at least one tenth and as much as a third of the Earth's biomass could be these tiny microbes living in the mud. However, this population lives at an unusual rate. Single-celled organisms usually consume food for energy and then rather than grow larger, simply divide and reproduce themselves. While the Bacteria Escherichia Coli, as an example, doubles its numbers every 20 minutes, these Archaea double on the order of hundreds or thousands of years and consume very little energy. ed.z.: Just wondering if perhaps these could be associated with deep oil formation?