Involvement of BmoR and BmoG in n-alkane metabolism in 'Pseudomonas butanovora'

'Pseudomonas butanovora' uses an alcohol-inducible alkane monooxygenase (BMO) to grow on C-2-C-9 n-alkanes. Five ORFs were identified flanking the BMO structural genes. Two of the ORFs, bmoR, encoding a putative sigma(54)-transcriptional regulator BmoR, and bmoG, encoding a putative GroEL chaperonin BmoG, were analysed by gene-inactivation experiments. The BmoR-deficient mutant grew at slower growth rates than the wild-type on C-2-C-5 n-alkanes and showed little to no growth on C-6-C-8 n-alkanes within 7 days. A BmoR-deficient mutant was constructed in the 'P. butanovora' bmoX::lacZ reporter strain and used to test whether bmoR was involved in bmoX induction after growth on C-2-C-8 carbon sources. In acetate- or lactate-grown cells, C-2-C-8 n-alcohols failed to induce beta-galactosidase activity. In contrast, in propionate-, butyrate- or pentanoate-grown cells, n-butanol induced similar to 45% of the beta-galactosiclase activity observed in the control bmoX::lacZ strain. In propionate-grown cells, C-2-C-5 n-alcohols induced beta-galactosidase activity, whereas C-7 and C-8 n-alcohols did not. BmoR may act as a sigma(54)-transcriptional regulator of bmo that is controlled by the n-alcohol produced in the alkane oxidation. During growth on short-chain-length fatty acids, however, another BMO regulatory system seems to be activated to promote transcription of bmo by short-chain-length alcohols (i.e. <= C-6). The bmoG-deficient mutant did not grow on C-2-C-8 n-alkanes; however, it was capable of transcribing bmoX and bmoC of the BMO operon. BmoG may act as a chaperonin to assemble competent BMO.