Biosynthesis and Bioactivity of Melanin from the Deep-Sea Hydrothermal Vent Yeast Hortaea werneckii Mo34

Importance of this study: Melanin synthesized through the oxidative polymerization of phenolic compounds exhibits a high molecular weight and has many physiological functions and activities. Main results: In this study, the key PKS1-1, PKS1-2, CMR1-1, and CMR1-2 genes for melanin biosynthesis and regulation from the highly genome-duplicated black yeast Hortaea werneckii Mo34, isolated from a deep-sea hydrothermal vent, were heterologously complemented in the ∆pks1 albino mutant K5 and the ∆cmr1 albino mutant CM7-2 of Aureobasidium melanogenum XJ5-1. Melanin formation in all the resulting transformants was restored, confirming that both the PKS1-1 and PKS1-2 genes from H. werneckii Mo34 were likely involved in the DHN melanin biosynthesis of A. melanogenum XJ5-1. Furthermore, the CMR1-1 and CMR1-2 genes from H. werneckii Mo34 could play significant roles in regulating melanin biosynthesis in A. melanogenum XJ5-1. Simultaneously, the expression of the PKS1 and THR1 genes involved in melanin biosynthesis was also enhanced in the transformants complemented with the CMR1-1 and CMR1-2 genes. The purified high-molecular-weight melanin from H. werneckii Mo34 exhibited excellent Fe2⁺-chelating, DPPH radical-scavenging, and superoxide radical-scavenging activities. Additionally, it actively inhibited the growth of Staphylococcus aureus and Pseudomonas putida. Conclusions: The black yeast H. werneckii Mo34 indeed had the DHN melanin biosynthesis pathway and the melanin produced by it had many potential applications.