Innovative approach for improvement of an antibiotic-overproducing industrial strain of Streptomyces albus.
Working with a Streptomyces albus strain that had previously been bred to produce industrial amounts (10 mg/ml) of salinomycin, we demonstrated the efficacy of introducing drug resistance-producing mutations for further strain improvement. Mutants with enhanced salinomycin production were detected at a high incidence (7 to 12%) among spontaneous isolates resistant to streptomycin (Str(r)), gentamicin, or rifampin (Rif(r)). Finally, we successfully demonstrated improvement of the salinomycin productivity of the industrial strain by 2.3-fold by introducing a triple mutation. The Str(r) mutant was shown to have a point mutation within the rpsL gene (encoding ribosomal protein S12). Likewise, the Rif(r) mutant possessed a mutation in the rpoB gene (encoding the RNA polymerase beta subunit). Increased productivity of salinomycin in the Str(r) mutant (containing the K88R mutation in the S12 protein) may be a result of an aberrant protein synthesis mechanism. This aberration may manifest itself as enhanced translation activity in stationary-phase cells, as we have observed with the poly(U)-directed cell-free translation system. The K88R mutant ribosome was characterized by increased 70S complex stability in low Mg(2+) concentrations. We conclude that this aberrant protein synthesis ability in the Str(r) mutant, which is a result of increased stability of the 70S complex, is responsible for the remarkable salinomycin production enhancement obtained.
Tamehiro
Norimasa
N
National Food Research Institute, Tsukuba, Ibaraki 305-8042, Japan.
Hosaka
Takeshi
T
Xu
Jun
J
Hu
Haifeng
H
Otake
Noboru
N
Ochi
Kozo
K
D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology*; D001709:Biotechnology / Q000379:methods; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D005839:Gentamicins / Q000494:pharmacology; D009154:Mutation; D011714:Pyrans / Q000378:metabolism*; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism; D012293:Rifampin / Q000494:pharmacology; D013302:Streptomyces / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D013307:Streptomycin / Q000494:pharmacology; D000095662:Polyether Polyketides
D000900:Anti-Bacterial Agents; D012321:DNA-Directed RNA Polymerases; D005839:Gentamicins; D011714:Pyrans; D012269:Ribosomal Proteins; D012293:Rifampin; D013307:Streptomycin; C034212:ribosomal protein S12; C010327:salinomycin; D000095662:Polyether Polyketides; C105078:RNA polymerase beta subunit