Quorum sensing regulates testosterone catabolic gene expression in Comamonas testosteroni

LINARES MAURICIO; GENTI DE RAIMONDI SUSANA

Villa Giardino. Córdoba

Congreso; XV Jornadas de la Sociedad de Biología de Córdoba; 2005

Sociedad de Biología de Córdoba

Quorum sensing (QS) is a cell density-dependent signaling system used by bacteria to coordinate gene expression within a population. QS systems in Gram negative bacteria consist of transcription factors of the LuxR family and a difussible small molecule called autoinducer. Previously, we identified a LuxR-type transcriptional factor called TeiR that positively regulates the transcription of genes involved in the initial enzymatic steps of steroid degradation in C. testosteroni (J.Bacteriol, 2004, 186:1430). In the present study, western blot assays demonstrated a TeiR density-dependent manner expression reaching peak levels at the stationary phase. The expression of a steroid-inducible transcriptional fusion (sip48- βhsd::lacZ) could be prematurely activated in cells at early to midexponential phase by the addition of ethyl acetate extracts obtained from the transition logaritmic-stationary-phase cell-free supernatants of C. testosteroni cultures grown in presence of testosterone. The gene loci teor, encoding acyl-coenzyme A [acyl- CoA] dehydrogenase homolog, tead encoding enoyl-CoA dehydratase homolog and tekt encoding a β-ketothiolase homolog were localized upstream of the teiR transcriptional regulator. To prove the essential involvement of teor, tead and tekt genes in the catabolism of testosterone in C. testosteroni, these genes were inactivated separately by the insertion of omega elements. The corresponding mutant strains were not able to grow on testosterone as well as to activate the sip48-βhsd::lacZ transcriptional fusion. Interestingly, the β-galactosidase activity of teor mutant complemented with a plasmid encoding teiR gene, can be restored by a diffusible extracellular factor (DSF) produced by C. testosteroni wt. In conclusion, the data demonstrate the necessity of a beta-oxidation cycle for testosterone degradation that results in an intermediary compound involved in QS signaling system