Synthesis of pulcherriminic acid by Bacillus subtilis

The pathway of pulcherriminic acid synthesis in Bacillus subtilis strains AM and AM-L11 (a leucine-requiring auxotroph) was investigated. Determinations of radioactivity in pulcherriminic acid synthesized by cells growing in media containing (14)C-labeled amino acids indicated that B. subtilis produced pulcherriminic acid from l-leucine. The organism utilized the carbon skeletons of two l-leucine molecules to synthesize one molecule of pulcherriminic acid. Similar results were obtained with starved cell suspensions. Growing cells formed significant amounts of pulcherriminic acid only in media including a carbohydrate such as starch. However, carbohydrate carbon was not required for the synthesis of pulcherriminic acid molecules. Data obtained with cell suspensions supported the hypothesis that cyclo-l-leucyl-l-leucyl is an intermediate in pulcherriminic acid biosynthesis and indicated that molecular oxygen is required for the conversion of cyclo-l-leucyl-l-leucyl to pulcherriminic acid. A pathway for the synthesis of pulcherrimin from l-leucine in B. subtilis is proposed.