49th Annual Meeting Deutsche Gesellschaft für Experimentelle und Klinische Pharmakologie und Toxikologie, Mainz, March 11-13, 2008

Abstract

Steroid contamination of sea water is an ever growing problem and impacts population dynamics of all kinds of sea animals. We have long experience with the soil bacterium Comamonas testosteroni which is able to catabolize a variety of steroids and polycyclic aromatic hydrocarbons, and which might be used in bioremediation of contaminated soil [1,2]. For our studies we use 3􀄮-hydroxysteroid dehydrogenase/carbonyl reductase (3􀄮-HSD/CR) as a reporter enzyme, since it is the key enzyme in steroid degradation [3,4]. Moreover, the expression of the corresponding gene, hsdA, is induced by environmental steroids. In previous investigations we have identified and described several genes being involved in hsdA regulation [1,2].In this work we isolated several bacterial strains from the Baltic Sea at Kiel, Germany, which degrade steroids and which are able to use 69 steroids as carbon source. One of them, strain H5, was characterized as being gram negative and showing resistance against ampicilline and carbenicilline. It could be best grown in SIN medium supplemented with 1.6–4.1% NaCl. More than 80% of cholesterol was digested when the strain was grown in SIN medium with 0.05 mM cholesterol. Western blots revealed that this salt water strain H5 expresses a 3􀄮-HSD/CR orthologous enzyme. Interestingly, 3􀄮-HSD/CR expression in strain H5 increased after induction with 0.3 mM testosterone, 0.3 mM estrogen or 0.05 mM cholesterol. Therefore, strain H5 might be used for the bioremediation of steroid contamination in sea water. Isolation of the 3􀄮-HSD/CR orthologous gene, as well as studies on its regulation and the generation of homologous hsdA knock-out strains of H5 are currently in progress. In addition, the exact characterization and systematic classification of this marine steroid degrading bacterial strain is envisaged