ANTIBIOTIC-RESISTANCE AND ENHANCED INSECTICIDE CATABOLISM AS CONSEQUENCES OF STEROID INDUCTION IN THE GRAM-NEGATIVE BACTERIUM COMAMONAS-TESTOSTERONI

The effects of steroid induction on antibiotic resistance against the fungal steroid fusidic acid (ramycin; 16-(acetyloxy)-3 alpha,11 a-dihy droxy-29-dammara-17(20),24-dien-21-oic-acid) as well as on carbonyl re duction and degradation of the novel anti-insect agent NKI 42255 dazol yl)-1-(4-methoxyphenyl)-2-methyl-1-propanone) were studied in the Gram -negative soil bacterium Comamonas testosteroni dagger strain ATCC 119 96. Cells grown with testosterone as inducing agent showed a 5-6-fold elevation of antibiotic resistance against the fungal steroid fusidic acid. Furthermore, testosterone induction caused a faster uptake and d ifferent metabolism of the anti-insect agent NKI 42255 compared to con trol cultures, revealing carbonyl reduction of the substrate keto grou p as an initial degradation step in induced cells. It is concluded tha t the formerly described steroid inducible hydroxysteroid dehydorgenas es/carbonyl reductases present in Comamonas testosteroni contribute to these altered phenotypes, thus establishing steroid-inducible catabol ic pathways as important defense processes against natural and synthet ic toxicants in certain bacteria, which are present in the intestinal microflora of mammalian species as well as in soil samples. Copyright (C) 1996 Elsevier Science Ltd.