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United States Department of Agriculture

Agricultural Research Service


item Delaney, Shannon
item Mavrodi, Dmitri
item Bonsall, Robert
item Thomashow, Linda

Submitted to: Journal of Bacteriology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Certain strains of root-colonizing fluorescent Pseudomonas bacteria have gained attention in recent years because they produce broad-spectrum metabolites active against fungal pathogens that cause soilborne root diseases. One such class of compounds, the phenazines, includes over 50 members with the same core structure but with different chemical modifications that largely determine their physical properties and biological activity against plant and animal pathogens. A common set of biosynthetic genes present in phenazine-producing strains is responsible for the synthesis of phenazine-1-carboxylic acid (PCA), but individual species differ in the range of compounds they produce. The purpose of this study was to determine why P. aureofaciens produces hydroxyphenazine compounds, which are more active than PCA against certain pathogenic fungi. We found that P. aureofaciens 30-84 has a novel gene that encodes an enzyme responsible for the conversion of PCA to 2-hydroxyphenazine. Knowledge of these genes responsible for phenazine product specificity could reveal ways to manipulate the bacteria to produce multiple phenazines or hybrid compounds not previously described. Such compounds may have improved activity against soilborne plant pathogens or lead to the development of novel pharmaceutical products.

Technical Abstract: Certain strains of root-colonizing fluorescent Pseudomonas spp. produce phenazines, a class of antifungal metabolites that can provide protection against various soilborne root pathogens. Despite the fact that the phenazine biosynthetic locus is highly conserved among fluorescent Pseudomonas spp., individual strains differ in the range of phenazine compounds they produce. This study focuses on the ability of Pseudomonas aureofaciens 30-84 to produce 2-hydroxyphenazine-1-carboxylic acid (2-OH- PCA) and 2-hydroxyphenazine (2-OH-PHZ) from the common phenazine metabolite phenazine-1-carboxylic acid (PCA). P. aureofaciens 30-84 contains a novel gene located downstream from the core phenazine operon that encodes for a 55-kD aromatic monooxygenase responsible for the hydroxylation of PCA to produce 2-OH-PCA. Knowledge of the genes responsible for phenazine product specificity could ultimately reveal ways to manipulate organisms to produce emultiple phenazines or novel phenazines not previously described.

Last Modified: 10/18/2017
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