The opportunistic pathogen Pseudomonas aeruginosa produces colorful redox-active metabolites called phenazines, which underpin biofilm development, virulence, and clinical outcomes. Although phenazines exist in many forms, the best studied is pyocyanin. Here, we describe pyocyanin demethylase (PodA), a hitherto uncharacterized protein that oxidizes the pyocyanin methyl group to formaldehyde and reduces the pyrazine ring via an unusual tautomerizing demethylation reaction. Treatment with PodA disrupts P. aeruginosa biofilm formation similarly to DNase, suggesting interference with the pyocyanin-dependent release of extracellular DNA into the matrix. PodA-dependent pyocyanin demethylation also restricts established biofilm aggregate populations experiencing anoxic conditions. Together, these results show that modulating extracellular redox-active metabolites can influence the fitness of a biofilm-forming microorganism.
Bibliographical noteFunding Information:
K.C.C. was supported by a Ruth L. Kirschstein National Research Service Award from the National Institute of Allergy and Infectious Diseases, NIH, grant no. F32AI112248. N.R.G. was supported by the National Science Foundation Graduate Research Fellowship, grant no. 1144469. This work was further supported by the Howard Hughes Medical Institute (HHMI), NIH (grant 5R01HL117328-03), and the Molecular Observatory at the Beckman Institute, California Institute of Technology and through the Gordon and Betty Moore Foundation and the Sanofi-Aventis Bioengineering Research Program at Caltech. Additional support was provided by the Stanford Synchrotron Radiation Lightsource, which is funded by the U.S. Department of Energy and NIH. S.J.C. thanks St. Hugh's College, Oxford for research support.