RESEARCH ARTICLE Loss of Homogentisate 1,2-Dioxygenase Activity in Bacillus anthracis Results in Accumulation of Protective Pigment

Melanin production is important to the pathogenicity and survival of some bacterial patho-gens. In Bacillus anthracis, loss of hmgA, encoding homogentisate 1,2-dioxygenase, results in accumulation of a melanin-like pigment called pyomelanin. Pyomelanin is produced in the mutant as a byproduct of disrupted catabolism of L-tyrosine and L-phenylalanine. Accu-mulation of pyomelanin protects B. anthracis cells from UV damage but not from oxidative damage. Neither loss of hmgA nor accumulation of pyomelanin alter virulence gene expres-sion, sporulation or germination. This is the first investigation of homogentisate 1,2-dioxy-genase activity in the Gram-positive bacteria, and these results provide insight into a conserved aspect of bacterial physiology