Improvement of A21978C production in Streptomyces roseosporus by reporter-guided rpsL mutation selection

Abstract

Daptomycin, one of the A21978C factors produced by Streptomyces roseosporus, is an acidic cyclic lipopeptide antibiotic with potent activity against a variety of Gram-positive pathogens. To increase the titre of this extensively used and clinically important antibiotic, we applied a reported-guided rpsL mutation selection system to generate strains producing high levels of A21978C. In the reporter design, dptE was chosen as the overexpressing target, and neo-encoding neomycin phosphotransferase as the reporter. Using this reporter-guided selection system, 20% of the selected, streptomycin-resistant mutants produced greater amounts of A21978C than the starting strain. The selection system increased the screening efficiency about 10-fold with a frequency of 1·7% A21978C overproducing strains among str(r) mutants. A21978C production was increased approximately 2·2-fold in the rpsL K43N mutant. The combination of ribosome engineering and reporter-guided mutant selection generated an A21978C overproducing strain that produced about twice as much A21978C as the parental strain. The strategies presented here, which integrated the advantages of both ribosome engineering and reporter-guided mutation selection, could be applied to other bacteria to improve their yield of secondary metabolites.