Formation of C₄–C₇ hydrocarbons from bacterial degradation of naturally occurring terpenoids

Abstract

We have recently found many light hydrocarbons, both alkanes and alkenes, in trace amounts (ng compound per g sediment) in Recent marine sediments^1–4. These hydrocarbons are believed to originate from both biological and low-temperature reactions in the sediments. Understanding their mechanism of formation may allow use of these compounds to decipher the past biological and thermal history of the sediments⁴. To investigate biological origins, we have cultivated mixed populations of bacteria on natural terpenoids and found, as degradation products, both alkanes and alkenes in the C₁–C₇ range; this is the first report of C₄–C₇ hydrocarbons being formed from microbial activities. Aerobic followed by anaerobic degradation yielded mainly small amounts of straight-chain alkenes. No such products resulted from blanks or controls. The results are consistent with products observed in natural environments.