BACTERIA CAN PENETRATE ROCK

Abstract

A method is described for studying the penetration of bacteria in intact rock cores. The test microorganism (Serratia marcescens ATCC No. 274) was labelled with radioactive phosphorus (32P) and suspended in sterile demineralized water. The cell suspension was allowed to enter the epoxy-coated rock core under atmospheric pressure. Penetration and migration of the labelled microorganisms were followed by measuring the radiation emitted at ports drilled through the epoxy coating, at various locations throughout the length of the core, and at various intervals of time after the beginning of the experiment. When migration was considered to be complete the core was aseptically split longitudinally and the results of the radiation studies confirmed by autoradiogram and culture. S. marcescens passed through 14.25 in. of Berea sandstone (the longest core available), and through 3-in. cores (longest available) of Mississippian limestone, Early Devonian limestone, and Late Mesozoic sandstone. The significance of these findings is discussed with respect to presence of so-called prehistoric microorganisms in geological specimens.