Diversity of the transcriptional regulation of the pch gene cluster in two indigenous p-cresol-degradative strains of Pseudomonas fluorescens.
p-Cresol methylhydroxylase (PCMH), a key enzyme responsible for the catabolism of p-cresol via the protocatechuate ortho pathway, was used as a tool to characterize catabolic differences between phenol- and p-cresol-degrading Pseudomonas fluore-scens strains PC18 and PC24. Although both strains catabolize p-cresol using PCMH, different whole-cell kinetic parameters for this compound were revealed. Affinity for the substrate and the specific growth rate were higher in PC18, whereas maximum p-cresol tolerance was higher in PC24. In addition, PCMH of strain PC18 was induced during growth on phenol. In both strains, the pchACXF operon, which encodes p-hydroxybenzaldehyde dehydrogenase and PCMH, was sequenced. Transcriptional regulation of these operons by PchR, a putative sigma(54)-dependent regulator, was shown. Although the promoters of these operons resembled sigma(54)-controlled promoters, they differed from the consensus sequence by having T instead of C at position -12. Complementation assays confirmed that the amino acid sequence differences of the PchR regulators between the two strains studied led to different effector-binding capabilities of these proteins: (1) phenol was a more efficient effector for PchR of PC18 than p-cresol, (2) phenol did not activate the regulator of PC24, and (3) both regulators responded similarly to p-cresol.
Jõesaar
Merike
M
Institute of Molecular and Cell Biology, Tartu University, Tartu, Estonia. merike.joesaar@ut.ee
Heinaru
Eeva
E
Viggor
Signe
S
Vedler
Eve
E
Heinaru
Ain
A
D000595:Amino Acid Sequence; D003408:Cresols / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D006899:Mixed Function Oxygenases / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family; D009876:Operon; D010084:Oxidation-Reduction; D019800:Phenol / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011551:Pseudomonas fluorescens / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013379:Substrate Specificity; D014158:Transcription, Genetic
D003408:Cresols; D004269:DNA, Bacterial; C032538:4-cresol; D019800:Phenol; D006899:Mixed Function Oxygenases; C049502:4-cresol dehydrogenase (hydroxylating)