Disruption of hmgA by DNA Duplication is Responsible for Hyperpigmentation in a Vibrio anguillarum Strain

Abstract

AbstractVibrio anguillarum531A, isolated from a diseased fish in the Atlantic Ocean, is a mixture composed of about 95 and 5% of highly pigmented cells (strain 531Ad) and cells with normal levels of pigmentation (strain 531Ac), respectively. Analysis of theV.anguillarum531Ad DNA region encompassing genes involved in the tyrosine metabolism showed a 410-bp duplication within thehmgAgene that results in a frameshift and early termination of translation of the homogentisate 1,2-dioxygenase. We hypothesized that this mutation results in accumulation of homogentisate that is oxidized and polymerized to produce pyomelanin. Introduction inE.coliof recombinant clones carrying theV.anguillarum hppD(4-hydroxyphenylpyruvate-dioxygenase), and a mutatedhmgAproduced brown colored colonies. Complementation with a recombinant clone harboringhmgArestored the original color to the colonies confirming that in the absence of homogentisate 1,2-dioxygenase the intermediary in tyrosine catabolism homogentisate accumulates and undergoes nonenzymatic oxidation and polymerization resulting in high amounts of the brown pigment. Whole-genome sequence analysis showed thatV.anguillarum531 Ac and 531Ad differ in thehmgAgene mutation and 23 mutations, most of which locate to intergenic regions and insertion sequences.