PART PLAYED BY BACTERIA IN PETROLEUM FORMATION 1

Biochemlcally versatile bacteria, capable of catalyzing a good many chemical reactions, occur abundantly in recent marine sediments. Living bacteria detected in certain petrollferous formations at appreciable depths are believed to be indigenous species in a state of dynamic equilibrium with their environment. If petroleum is formed from organic matter, it is almost axiomatic that bacteria have con-tributed to the process, because the organic remains of both plants and animals are susceptible to microbial modification. In recent marine sediments bacteria tend to convert organic om-pounds into humus and other substances approaching the elementary composition ofcrude oiI. Besides producing methane as an end-product of metabolism, certain bacteria synthesize small quantities of liquid and solid hydrocarbons a an integral part of their cell substance. Anaerobic bacteria formal in sediments catalyze the oxidation of molecular hydrogen with the formation of methane, hy'drogen sulfide, saturated compounds, and other substances that may occur in oil tields. Crude oil in contact with water may be slowly modified in various ways by bacterial activ-ity. Bacteria may contribute to the migration and accumulation of oil by pronmting its libera-tion from oil-bearing sediments. Although many theories have been advanced (Brooks, 1936; Skelton and Skelton, 1942) to account for the origin of oil, the reactions resulting in the formation of petroleum are still obscure. It is generally agreed, however, by pe-troleum geologists (Cox, 1946) that crude oil was formed from the organic rentaius of plants and/or animals in a marine environment at pressures mostly less that 5,000 psi, and at relatively low temperatures, the maximum being in the neighborhood of 100°C. for most oil basins. Based upon the premise that organic matter is the mother substance of petroleum, it is almost axiomatic that bacteria nd allied microorganisms must have contributed to the process, becaus