Bacterial Metabolism of Steroids

Abstract

Steroids are naturally occurring hydrophobic molecules frequently found in the biosphere. Currently, a considerable amount of steroid hormones are released into the environment as a result of human activity being now considered a new class of pollutants. This fact is generating an increasing concern about its effects in the environment, because in spite of its ubiquity in nature, most of the steroidal compounds are highly recalcitrant to microbial degradation. Bacterial transformation of steroid compounds has attracted increasing interest due to the biotechnological applications since sterol-degrading microorganisms have already been used for industrial production of steroidal drugs from low-cost natural sterols such as phytosterols. In these bacteria, a large set of catabolic genes has been identified based on gene annotation and biochemical and transcriptomic analyses. The recent knowledge on the microbial metabolism of steroids is reviewed by describing the steps involved in the catabolic pathways under both aerobic and anaerobic conditions. This background information will be helpful for metabolic engineering of steroid-transforming bacteria for biotechnological applications.