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

Abstract

Vibrio anguillarum 531A, 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 the V. anguillarum 531Ad DNA region encompassing genes involved in the tyrosine metabolism showed a 410-bp duplication within the hmgA gene 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 in E. coli of recombinant clones carrying the V. anguillarum hppD (4-hydroxyphenylpyruvate-dioxygenase), and a mutated hmgA produced brown colored colonies. Complementation with a recombinant clone harboring hmgA restored 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 that V. anguillarum 531 Ac and 531Ad differ in the hmgA gene mutation and 23 mutations, most of which locate to intergenic regions and insertion sequences.

Assessing the effects of β-triketone herbicides on HPPD from environmental bacteria using a combination of in silico and microbiological approaches

“…HPPD protein sequences of the three bacteria previously studied were aligned (Supplementary Information 3), together with the HPPD of R. etli CFN42, which was available online and was part of our first experiment, and five others HPPD sequences from different bacteria strains, whose pyomelanin production has been described [13,19,63,64]. Even though these nine sequences have relatively low similarity, ranging from 35.26 to 87.39%, they retain some highly conserved regions.…”

“…This brown pigment is easily observable on culture media supplemented with L-tyrosine, and its production has been described in various microbial species such as fungi and yeasts [9][10][11][12] and in numerous bacterial species such as Legionella pneumophila, Shewanella oneidensis, Streptomyces avermitilis, Burkholderia cenocepacia, Bacillus thuringiensis, Alteromonas stellipolaris, Rubrivivax benzoatilyticus, Klebsiella pneumoniae, Alacaligenes faecalis, Enterobacter sp. and Vibrio angillarum [13][14][15][16][17][18][19][20][21]. Some of these studies report either a protective role of pyomelanin against environmental stresses, such as reactive oxygen species for the soil-borne plant pathogen Ralstonia solanacearum [22], light for L. pneumophila [23], ultraviolet irradiation for the marine bacteria Vibrio splendidus [24], or a modification in virulence for pathogenic bacteria [19],…”

“…and Vibrio angillarum [13][14][15][16][17][18][19][20][21]. Some of these studies report either a protective role of pyomelanin against environmental stresses, such as reactive oxygen species for the soil-borne plant pathogen Ralstonia solanacearum [22], light for L. pneumophila [23], ultraviolet irradiation for the marine bacteria Vibrio splendidus [24], or a modification in virulence for pathogenic bacteria [19],…”