A variety of bacteria produce natural phenazine antibiotics. In addition to helping the organisms compete with other bacteria, these heterocyclic nitrogen containing compounds can also act as virulence factors. A well-studied example is pyocyanin, a phenazine produced by Pseudomonas aeruginosa that has been implicated in its ability to infect the lungs of cystic fibrosis patients. This is the 1.5Å resolution crystal structure of PhzF from Bacillus anthrasis, an essential isomerase in the phenazine synthesis pathway. The molecule acts as a dimer and is believed to use a conserved glutamic acid to remove a proton from C3 of the substrate trans-2,3-dihydro-3-hydroxyanthranilic acid. Other structural examples of PhzF have previously been solved from organisms such as Pseudomonas fluorescens (1T6K) and Enterococcus faecalis (1S7J).