Sunday, July 24, 2011
Grand Ballroom, 5th fl (Sheraton New Orleans)
Steroid drugs are used to treat a wide variety of diseases spanning oncology, gynecology, rheumatology, and more. The manufacture of these drugs has a large requirement for raw materials, and can be quite energy intensive and expensive. When possible, microbial transformations are used to reduce the cost, energy requirement, and use of hazardous reagents during steroid manufacturing. However, knowledge of microbial steroid transport and metabolism is very limited; a better understanding of these processes is required to fully harness the power of microorganisms for steroid manufacture. The gram-positive Actinomycete, Rhodococcus jostii RHA1 has a cholesterol degradation pathway that is well-characterized. Additionally, it has a set of genes homologous to those encoding cholesterol degradation that are upregulated during growth on cholic acid. In this study, we investigated two novel transporters associated with cholic acid catabolism. Reverse-transcriptase quantitative-PCR indicated that both an ABC transporter and an MFS transporter were upregulated during growth on cholic acid. With gene knockout analysis, we discovered that these transporters are required for re-assimilation of distinct cholic acid metabolites and for maximal growth on cholic acid. We determined the structures of these metabolites with gas chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy and found that the metabolites are novel. Thus, we found unexpected transport processes during cholic acid metabolism that may be critical to applications involving bacterial steroid transformation.