A Cure for the Common Mold.

This article reports that Alexander Fleming's famous mold, Penicillium notatum, didn't make much of the antibiotic, and industry turned to alternate strains to ramp up production. A new report shows that a single enzymatic mutation made all the difference. Scientists employed P. notatum during early attempts to manufacture penicillin, but they later abandoned it favor of a more promising species of mold, P. chrysogenum, discovered on a cantaloupe in 1943. The key difference was how the strains metabolize phenylacetic acid (PA), a precursor of penicillin. Mold can convert PA into either penicillin or 2-hydroxy-PA, a product formed by the enzyme expressed from a gene called pahA .