... Science Frontiers ONLINE No. 85: Jan-Feb 1993 Issue Contents Other pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects Biogeology It is accepted that every cubic centimeter of the topsoil beneath our feet seethes with thousands of microorganisms. It is less well known that life's domain extends down much further. The hard rocks and strata of earth's crust -- seemingly sterile and inert -- are continuously being transformed by bacteria and other life forms. In fact, it was easy to find three examples of such processes from the literature collected from the past two months. Although the discoveries reported below may seem dull to anomalists ued to more exciting fare, it may well be that life from "inner space" has been and will be more important to humankind than life from "outer space," as implied in third item! Bacteria and placer gold. "Lacelike networks of micrometresize filiform gold associated with Alaskan placer gold particles are interpreted as low-temperature pseudomorphs of a Pedomicrobium -like budding bacterium. Submicron reproductive structures (hyphae) and other morphological features similar to those of Pedomicrobium occur as three-dimensional facsimiles in highpurity gold in and on placer gold particles from Lillian Creek, Alaska." In short, bacteria help create placer gold deposits. The author believes that bacterioform gold is widespread. (Watterson, John R.; "Preliminary Evidence for the Involvement of Budding Bacteria in the Origin of Alaskan Placer Gold," Geology , 20:315, 1992.) Microorganisms and iron deposits. At least 500 million years ago ...