ABSTRACT
Phenazines are a class of bacterially produced redox-active metabolites that are found in natural, industrial, and clinical environments. In
Pseudomonas
spp., phenazine-1-carboxylic acid (PCA)—the precursor of all phenazine metabolites—facilitates nutrient acquisition, biofilm formation, and competition with other organisms. While the removal of phenazines negatively impacts these activities, little is known about the genes or enzymes responsible for phenazine degradation by other organisms. Here, we report that the first step of PCA degradation by
Mycobacterium fortuitum
is catalyzed by a
ph
enazine-
d
egrading decarboxylase (PhdA). PhdA is related to members of the UbiD protein family that rely on a prenylated flavin mononucleotide cofactor for activity. The gene for PhdB, the enzyme responsible for cofactor synthesis, is present in a putative operon with the gene encoding PhdA in a region of the
M. fortuitum
genome that is essential for PCA degradation. PhdA and PhdB are present in all known PCA-degrading organisms from the
Actinobacteria
.
M. fortuitum
can also catabolize other
Pseudomonas
-derived phenazines such as phenazine-1-carboxamide, 1-hydroxyphenazine, and pyocyanin. On the basis of our previous work and the current characterization of PhdA, we propose that degradation converges on a common intermediate: dihydroxyphenazine. An understanding of the genes responsible for degradation will enable targeted studies of phenazine degraders in diverse environments.
IMPORTANCE
Bacteria from phylogenetically diverse groups secrete redox-active metabolites that provide a fitness advantage for their producers. For example, phenazines from
Pseudomonas
spp. benefit the producers by facilitating anoxic survival and biofilm formation and additionally inhibit competitors by serving as antimicrobials. Phenazine-producing pseudomonads act as biocontrol agents by leveraging these antibiotic properties to inhibit plant pests. Despite this importance, the fate of phenazines in the environment is poorly understood. Here, we characterize an enzyme from
Mycobacterium fortuitum
that catalyzes the first step of phenazine-1-carboxylic acid degradation. Knowledge of the genetic basis of phenazine degradation will facilitate the identification of environments where this activity influences the microbial community structure.
Integrated circuit-based electrochemical sensor for spatially resolved detection of redox-active metabolites in biofilms
