Product Repression of Alkane Monooxygenase Expression in Pseudomonas butanovora

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Abstract
Physiological and regulatory mechanisms that allow the alkane-oxidizing bacterium Pseudomonas butanovora to consume C 2 to C 8 alkane substrates via butane monooxygenase (BMO) were examined. Striking differences were observed in response to even- versus odd-chain-length alkanes. Propionate, the downstream product of propane oxidation and of the oxidation of other odd-chain-length alkanes following β-oxidation, was a potent repressor of BMO expression. The transcriptional activity of the BMO promoter was reduced with as little as 10 μM propionate, even in the presence of appropriate inducers. Propionate accumulated stoichiometrically when 1-propanol and propionaldehyde were added to butane- and ethane-grown cells, indicating that propionate catabolism was inactive during growth on even-chain-length alkanes. In contrast, propionate consumption was induced (about 80 nmol propionate consumed · min −1 · mg protein −1 ) following growth on the odd-chain-length alkanes, propane and pentane. The induction of propionate consumption could be brought on by the addition of propionate or pentanoate to the growth medium. In a reporter strain of P. butanovora in which the BMO promoter controls β-galactosidase expression, only even-chain-length alcohols (C 2 to C 8 ) induced β-galactosidase following growth on acetate or butyrate. In contrast, both even- and odd-chain-length alcohols (C 3 to C 7 ) were able to induce β-galactosidase following the induction of propionate consumption by propionate or pentanoate.