Melanin Synthesis in Bacteria: Who, How and Why

Abstract

There are different pathways leading to the synthesis of several kinds of melanin in Nature, most of which have been found in bacteria. In some of them, melanin production involves specific enzymes such as tyrosinases and laccases, while in others melanin formation results from genetic and/or metabolic alterations in tyrosine metabolism. In addition, some less frequent pathways are also found. Melanin biosynthesis in bacteria is subject to metabolic and genetic control involving both global and specific regulators but several facets remain to be elucidated. The capability to synthesize melanin has been described in many Proteobacteria and Actinobacteria and a few other groups including some Firmicutes, but environmental mining studies and genome analysis suggest that the capability to synthesize melanin among bacteria is widespread. Melanin has been observed to increase microbial survival in diverse environments and affect the interaction of bacteria with other microorganisms or with their hosts, with an important role both in mutualistic and pathogenic interactions.