Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: 6/3/1999
Publication Date: N/A
Technical Abstract: Bacteria that can degrade several kinds of aromatic acids often do so in a preferential order. For example, given a mixture of benzoate and 4-hydroxybenzoate (4-HBA), Pseudomonas putida always degrades benzoate first. We have shown that this preference is regulated, at least in part, at the transcriptional level since expression of pcaK, a gene from the 4-HBA degradation regulon, is repressed by benzoate when 4-HBA is present as an inducer. To probe the mechanism of benzoate repression further, we isolated transposon mutants that were unable to grow on benzoate. Among these was a mutant disrupted in a regulatory gene that we have termed benR. The deduced amino acid sequence of BenR shows high similarity to XylS (62% identical), a positive regulator of the AraC family that regulates xylene degradation in P. putida. We determined that BenR activates genes required for benzoate degradation. It is also required for benzoate-mediated repression of pcaK-lacZ fusion expression and thus appears to play a role in regulating 4-HBA degradation. These results indicate that BenR serves as both a positive and negative transcriptional regulator and that it functions to allow P. putida to degrade aromatic acids in a preferred sequence.