Chemotaxis by Pseudomonas putida (ATCC 17453) Towards Camphor Involves Cytochrome P450cam (CYP101A1)

The camphor-degrading microorganism, Pseudomonas putida strain ATCC 17453, is an aerobic, gram-negative soil bacterium that uses camphor as its sole carbon and energy source. The genes responsible for the catabolic degradation of camphor are encoded on the extra-chromosomal CAM plasmid. A monooxygenase, cytochrome P450cam, mediates hydroxylation of camphor to 5-exo-hydroxycamphor as the first and committed step in the camphor degradation pathway, requiring a dioxygen molecule (O2) from air. Under low O2 levels, P450cam catalyzes the production of borneol via an unusual reduction reaction. We have previously shown that borneol downregulates the expression of P450cam. To understand the function of P450cam and the consequences of down-regulation by borneol under low O2 conditions, we have studied chemotaxis of camphor induced and non-induced P. putida strain ATCC 17453. We have tested camphor, borneol, oxidized camphor metabolites and known bacterial attractants (D)-glucose, (D) - and (L)-glutamic acid for their elicitation chemotactic behavior. In addition, we have used 1-phenylimidazole, a P450cam inhibitor, to investigate if P450cam plays a role in the chemotactic ability of P. putida in the presence of camphor. We found that camphor, a chemoattractant, became toxic and chemorepellent when P450cam was inhibited. We have also evaluated the effect of borneol on chemotaxis and found that the bacteria chemotaxed away from camphor in the presence of borneol. This is the first report of the chemotactic behaviour of P. putida ATCC 17453 and the essential role of P450cam in this process.