Seventy-five meters beneath the surface of a site in Idaho where radioactive waste has been stored for more than 40 years, microorganisms living in the pores and crevices of dry basaltic rock are able to reduce a toxic form of chromium to a much less toxic form — and they do so faster in the presence of volatile organic wastes.
http://www2.lbl.gov/Science-Articles/Archive/bug-eating-microbes.html