Utilization of geraniol is dependent on molybdenum in Pseudomonas aeruginosa:: evidence for different metabolic routes for oxidation of geraniol and citronellol

Mini-Tn5-induced mutants with defects in utilization of linear terpenes such as citronellol, geraniol, citronellate and/or geranylate were isolated from Pseudomonas aeruginosa. One mutant was unable to utilize geraniol but showed wild-type growth with the three other acyclic terpenes tested. The Tn5 insertion site of the mutant was determined by DNA sequencing. Comparison with the P. aeruginosa genome sequence revealed that PA3028, an ORF with high similarity on the amino acid level to molybdenum cofactor biosynthesis protein A2 (encoded by moeA2), was the target of mini-Tn5 in the mutant. Disruption of moeA2 in P. aeruginosa PAO1 wild-type by insertion mutagenesis resulted in the same geraniol-minus phenotype. The ability to utilize geraniol was restored to the mutant by conjugative transfer of PCR-cloned wild-type moeA2 on a broad-host-range plasmid. Growth of P. aeruginosa PAO1 on geraniol and geranial, but not on citronellol, citronellate or geranylate, was inhibited by the presence of 10 mM tungstate, a molybdenum-specific inhibitor. Inhibition by tungstate was prevented by addition of molybdate. The results indicate that at least one step in the oxidation of geraniol to geranic acid (geranial oxidation) is a molybdenum-dependent reaction in P. aeruginosa and is different from the molybdenum-independent oxidation of citronellol to citronellate.