Characterization of water-soluble dark-brown pigment from Antarctic bacterium, Lysobacter oligotrophicus

Lysobacter oligotrophicus strain 107-E2(T) isolated from Antarctica produces dark-brown colored water-soluble pigment, in addition to hydrolases and lytic enzymes. The production of pigment is a common characteristic among members of the genus Lysobacter, but the identity of the pigments has been unknown. In this study, we identified the pigment from L. oligotrophicus as melanin pigment (Lo-melanin) by chemical and spectroscopic analyses. Although melanin is generally insoluble in both aqueous and organic solvents, the results in this study revealed that Lo-melanin shows water-solubility by means of the added polysaccharide chain. Lo-melanin production of L. oligotrophicus was increased by ultraviolet (UV) exposure, and survival rate of Escherichia coli under UV-irradiated condition was increased by the addition of Lo-melanin to the medium.