Advanced mutasynthesis studies on the natural α-pyrone antibiotic myxopyronin from Myxococcus fulvus.

Myxopyronin is a natural α-pyrone antibiotic from the soil bacterium Myxococcus fulvus Mx f50. Myxopyronin inhibits bacterial RNA polymerase (RNAP) by binding to a part of the enzyme not targeted by the clinically used rifamycins. This mode of action makes myxopyronins promising molecules for the development of novel broad-spectrum antibacterials. We describe the derivatization of myxopyronins by an advanced mutasynthesis approach as a first step towards this goal. Site-directed mutagenesis of the biosynthetic machinery was used to block myxopyronin biosynthesis at different stages. The resulting mutants were fed with diverse precursors that mimic the biosynthetic intermediates to restore production. Mutasynthon incorporation and production of novel myxopyronin derivatives were analyzed by HPLC-MS/MS. This work sets the stage for accessing numerous myxopyronin derivatives, thus significantly expanding the chemical space of f α-pyrone antibiotics.