Pyomelanin from Pseudoalteromonas lipolytica reduces biofouling

Abstract

SummaryMembers of the marine bacterial genus Pseudoalteromonas are efficient producers of antifouling agents that exert inhibitory effects on the settlement of invertebrate larvae. The production of pigmented secondary metabolites by Pseudoalteromonas has been suggested to play a role in surface colonization. However, the physiological characteristics of the pigments produced by Pseudoalteromonas remain largely unknown. In this study, we identified and characterized a genetic variant that hyperproduces a dark‐brown pigment and was generated during Pseudoalteromonas lipolytica biofilm formation. Through whole‐genome resequencing combined with targeted gene deletion and complementation, we found that a point mutation within the hmgA gene, which encodes homogentisate 1,2‐dioxygenase, is solely responsible for the overproduction of the dark‐brown pigment pyomelanin. In P. lipolytica, inactivation of the hmgA gene led to the formation of extracellular pyomelanin and greatly reduced larval settlement and metamorphosis of the mussel Mytilus coruscus. Additionally, the extracted pyomelanin from the hmgA deletion mutant and the in vitro‐synthesized pyomelanin also reduced larval settlement and metamorphosis of M. coruscus, suggesting that extracellular pyomelanin released from marine Pseudoalteromonas biofilm can inhibit the settlement of fouling organisms.

Characterization of a nontoxic pyomelanin pigment produced by the yeast Yarrowia lipolytica

“…25 The solubility of dried purified brown pigment was evaluated in different solvents as previously described. 38 The pigment was found to be insoluble in organic solvents namely chloroform, These solubility properties are in agreement with those reported for other melanin pigments. [38][39][40] The purified brown pigment was then analyzed by Fourier transformation infra-red microspectroscopy (FTIR) (Figure 2).…”

“…For further characterizations, the brown pigment was purified according to a published protocol . The solubility of dried purified brown pigment was evaluated in different solvents as previously described . The pigment was found to be insoluble in organic solvents namely chloroform, ethanol, acetone, methanol, poorly soluble in water and 1 M HCl solution.…”

“…These solubility properties are in agreement with those reported for other melanin pigments. The purified brown pigment was then analyzed by Fourier transformation infra‐red microspectroscopy (FTIR) (Figure ). The obtained spectra showed characteristic of aromatic compounds, which is in agreement with most melanin signals reported so far .…”

“… The purified brown pigment was then analyzed by Fourier transformation infra‐red microspectroscopy (FTIR) (Figure ). The obtained spectra showed characteristic of aromatic compounds, which is in agreement with most melanin signals reported so far . The occurrence of a large band of absorption between 3,670 and 3,000 cm −1 may indicates both the presence of OH groups and unsaturated carbon or aromatic group.…”

“…The obtained spectra showed characteristic of aromatic compounds, which is in agreement with most melanin signals reported so far. 3,4,38,40 The occurrence of a large band of absorption between 3,670 and 3,000 cm −1 may indicates both the presence of OH groups and unsaturated carbon or aromatic group. The three peaks between 3,000 and 2,700 cm −1 are generally assigned to the stretching vibration of aliphatic CH (Figure 2).…”