Physiological Analysis of the Expression of the Styrene Degradation Gene Cluster in Pseudomonas fluorescens ST

• DOI: 10.1128/aem.66.4.1305-1310.2000
• Publication Date: 2002-07-27T09:56:57Z
• Authors: Pedro Miguel Santos; Janet Martha Blatny; Ilaria Di Bartolo; Svein Valla; Elisabetta Zennaro
• Keywords: 0301 basic medicine; Recombinant Fusion Proteins; Gene Expression Regulation, Bacterial; Pseudomonas fluorescens; Carbon; 03 medical and health sciences; Biodegradation, Environmental; Bacterial Proteins; Lac Operon; Genes, Bacterial; Multigene Family; Operon; Promoter Regions, Genetic; Styrene

ABSTRACT

The effects of different carbon sources on expression of the styrene catabolism genes in Pseudomonas fluorescens ST were analyzed by using a promoter probe vector, pPR9TT, which contains transcription terminators upstream and downstream of the β-galactosidase reporter system. Expression of the promoter of the stySR operon, which codes for the styrene two-component regulatory system, was found to be constitutive and not subject to catabolite repression. This was confirmed by the results of an analysis of the stySR transcript in P. fluorescens ST cells grown on different carbon sources. The promoter of the operon of the upper pathway, designated P styA , was induced by styrene and repressed to different extents by organic acids or carbohydrates. In particular, cells grown on succinate or lactate in the presence of styrene started to exhibit β-galactosidase activity during the mid-exponential growth phase, before the preferred carbon sources were depleted, indicating that there is a threshold succinate and lactate concentration which allows induction of styrene catabolic genes. In contrast, cells grown on glucose, acetate, or glutamate and styrene exhibited a diauxic growth curve, and β-galactosidase activity was detected only after the end of the exponential growth phase. In each experiment the reliability of the reporter system constructed was verified by comparing the β-galactosidase activity and the activity of the styrene monooxygenase encoded by the first gene of the styrene catabolic operon.