The P-alkBFGHJKL promoter is under carbon catabolite repression control inPseudomonas oleovorans but not in Escherichia coli alk(+) recombinants

The alk genes are located on the OCT plasmid of Pseudomonas oleovorans and encode an inducible pathway for the utilization of n-alkanes as carbon and energy sources. We have investigated the influence of alternative carbon so urces on the induction of this pathway in P. oleovorans and Escherichia col i alk(+) recombinants. In doing so, we confirmed earlier reports that induc tion of alkane hydroxylase activity in pseudomonads is subject to carbon ca tabolite repression. Specifically, synthesis of the monooxygenase component AlkB is repressed at the transcriptional level. The alk genes have been cl oned into plasmid pGEc47, which has a copy number of about 5 to 10 per cell in both E, coil and pseudomonads. Pseudomonas putida GPo12 is a P. oleovor ans derivative cured of the OCT plasmid. Upon introduction of pGEc47 in thi s strain, carbon catabolite repression of alkane hydroxylase activity was r educed significantly. In cultures of recombinant E. coli HB101 and W3110 ca rrying pGEc47, induction of AlkB and transcription of the alkB gene were no longer subject to carbon catabolite repression, This suggests that carbon catabolite repression of alkane degradation is regulated differently in Pse udomonas and in E. coil strains, These results also indicate that P-alkBFGH JKL, the P-alk promoter, might be useful in attaining high expression level s of heterologous genes in E. coil grown on inexpensive carbon sources whic h normally trigger carbon catabolite repression of native expression system s in this host.