Melanin Synthesis in Bacteria: Who, How and Why

BEYOND UNIFORMITY: Pyomelanin’s structural complexity impacts on UV shielding inPseudomonasspecies with different lifestyles

“…In order to have a quantitative analysis on the melanin composition, three regions of the 1 H NMR spectra were integrated (Fig. S5-S9) for each sample: (1) the Ar region (7.6-6.3 ppm), corresponding to aromatic protons and given an arbitrary area of 1.00; (2) the RO region (4.6-3.4 ppm), associated to alkoxy moieties; and (3) the aliphatic region (2.8-0.4 ppm), attributed to alkyl residues (Table 2). The general pattern of the spectra was similar; however different ratios were detected for the three NMR regions that could explain the distinct behavior among the strains.…”

“…In bacteria, particularly in Pseudomonas species spontaneous pyomelanin production, derived of the alteration in the homogentisate pathway, was only reported for P. aeruginosa (2,15) and P. stutzeri (16). In another Pseudomonas species, DOPA melanin is produced by specific enzymes due to the orthohydroxylation of tyrosine to 3,4-dihydroxyphenylalanine (DOPA) and the subsequent transformations that end in the polymerization (3). The structure of melanin is not unique due to its heterogeneous nature (17).…”

“…The specific inhibitor bicyclopyrone[4-hydroxy-3-(2-(2-methoxy-ethoxymethyl)-6-trifluoromethyl-pyridine-3-carbonyl)-bicyclo (3,2,1) oct-3-en-2-one] (ACURON TM UNO, Syngenta Agro S.A.) was used to analyze the relevance of HppD. Different concentrations (0.1 mM, 1 mM, and 10 mM) of this inhibitor were added to test tubes cultures performed in LB medium as previously described.…”

“…In wild type strains, homogentisate is converted by different enzymes in fumarate and acetoacetate as final products which get into central metabolism. Alterations in the homogentisate pathway leading to spontaneous production of pyomelanin are frequently observed in nature (3). It has been found that melanins confer adaptive advantages by increasing fitness under stressful conditions of bacteria having different lifestyles (4).…”