Formation of melanin pigment by a mutant of Bacillus thuringiensis H-14

A mutant of Bacillus thuringiensis H-14 produced a dark brown pigment during sporulation. Production of the pigment depended on the nutritional properties of the growth medium. The pigment was identified as melanin, based on chemical tests and its infra-red spectrum. Incorporation of L-tyrosine in the culture medium enhanced the level of melanin production, and L-3,4-dihydroxyphenylalanine (L-DOPA) was detected in the culture broth during the late-exponential phase of growth. This indicates that the pathway of melanin synthesis is from L-tyrosine, via L-DOPA, to melanin.