By pairing genome mining with imaging mass spectrometry, chemists have uncovered a molecular player in a disease that makes button mushrooms rot into a stinking slime (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201206658). Soft rot is caused by the microbe Janthinobacterium agaricidamnosum, but its chemical mediators were unknown. Christian Hertweck of Germany’s Leibniz Institute for Natural Product Research & Infection Biology and colleagues mined the microbe’s genome for mushroom-killing potential. They found a promising cluster of genes, but it was inactive in lab-cultured bacteria. They eventually found a chemical culprit by analyzing mass spectrometry profiles of mushroom slices. The molecule, which they call jagaricin, is a cyclic lipopeptide. Applying jagaricin to mushrooms produces lesions similar to those in soft rot, although the researchers note that jagaricin isn’t necessarily acting alone. Because mushrooms are fungi, the team also checked whether jagaricin might be useful against fungi that infect people. In petri dishes, it killed the fungus behind yeast infections, among others.