Fig 1. Pulcherrimin Biosynthesis, Transport, and Regulation in B. subtilis.

A) Pulcherriminic acid biosynthesis by the cyclization of tRNA-charged leucines to form cyclo(L-leucine-leucine) and the subsequent oxidation by CypX to form water-soluble pulcherriminic acid. Pulcherriminic acid is then transported out of the cell by YvmA, where it can form the insoluble pulcherrimin complex with iron, which forms a red color and has a peak absorbance at 410 nm. B) Genetic architecture of the pulcherrimin cassette. PchR, the MarR-family regulator encoded within the cassette, negatively regulates two promoters controlling pchR-yvmA and yvmC-cypX expression [13].