Melanization of the Wood-Staining Fungus Aureobasidium Pullulans in Response to UV Radiation

Aureobasidium pullulans is a dark yeast-like fungus that commonly colonizes weathered wood surfaces. We isolated black melanized strains of A. pullulans from weathered southern pine wood and also a less common white strain. In this study, we test if this white strain is a melanin-deficient strain or one that melanizes when it is exposed to UV light. White and black strains of A. pullulans were grown on artificial media under UV radiation, visible light, or in the dark for 7 days, and their color and melanin contents were measured. The white strain was lighter and produced significantly less melanin when grown in the dark than the black strain. However, the white strain melanized and became darker when grown under UV and visible light, and after 1 wk of exposure to UV light, its hyphal melanin content was similar to that of the black strain, although the latter had also melanized and become darker on exposure to UV light. We conclude that the white strain of A. pullulans we isolated from weathered wood is a strain with the adaptive ability to melanize after exposure to UV light