Résumé
Xanthomonas albilineans, which causes leaf scald disease of sugarcane, produces a highly potent pathotoxin and antibiotic called albicidin that was shown to inhibit DNA replication in both sugarcane proplastids and Escherichia coli. Low yields of albicidin production in slow growing X. albilineans have slowed studies of its chemical structure and potential therapeutic applications. Albicidin is synthesized by a unique hybrid PKS/NRPS (polyketide synthase/nonribosomal peptide synthase) pathway that does not resemble any other described to date. We report here the transfer of the entire 49 kb albicidin biosynthetic gene cluster from X. albilineans into X. axonopodis pv. vesicatoria and the subsequent production of an antibiotic active against E. coli that shows cross-resistance with albicidin. The yield of this antibiotic in X. axonopodis pv. vesicatoria is 6 times higher than in X. albilineans. This study demonstrates the feasibility to transfer the albicidin pathway into an heterologous host and offers a promising strategy to overproduce, characterize and explore potential therapeutic applications of this potent antibiotic. (Texte intégral)