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Abstract

Castellaniella defragrans is a facultative anaerobic betaproteobacterium, which is able to degrade monoterpenes under denitrifying anoxic conditions. Proteomic studies on phellandrene-grown cells showed the up-regulation of a putative Resistance-Nodulation-Division (RND) transporter (AmeABCD). RND transporters are known to be involved in the export of toxic compounds to avoid cell damage. Transposon and deletion mutants of the AmeABCD cassette showed impaired growth on monoterpenes. Similarly growth on limonene of wild-type cells was inhibited by the addition of efflux pump inhibitors 1- (1-naphthylmethyl)piperazine (NMP) and phenyl arginine β-naphthylamide (PAβN). Monitoring of bacterial growth on acyclic and monocyclic monoterpene alcohols revealed that the gene cassette ameABCD is not essential for growth on perillyl alcohol. Growth on linalool and geraniol is reduced with ameABCD. The evidences suggest that the RND transporter might be involved not only in the detoxification of the cell membrane from linalool and geraniol but also in both export and uptake of the apolar monoterpene limonene. The mutant with transposon in ameB showed a bigger deviation than deletion mutant in comparison to wildtype in growth on geraniol and perillyl alcohol. This could indicate ameB as regulator of transport.