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[The characterization of mutant No. 68 from midecamycin producing strain S. mycarofaciens 1748]
Abstract:
A stable mutant No. 68 was obtained by treatment of S. mycarofaciens 1748 spores at high temperature. The electromicroscopic examination has shown that the mutant No. 68 and parent strain 1748 both have the spore chains of the spiratype. The spores of both strain are cylindrical in shape. The only difference is that the spores of the mutant No. 68 are of smooth surface, but the 1748 are of thorny. The physiological characteristics of both strains are also very similar with slight differences in utilization of few carbon sources and in cultural characters in few medium. Feeding experiment has shown that the mutant No. 68 was blocked in the formation of the macrolide lactone in the midecamycin biosynthetic pathway. This suggested that the mutant No. 68 might be a polyketide synthase genes deficient mutant. The ability of the mutant No. 68 to convert spiramycin into 4"-propionylspiramycin indicated that the mutant No. 68 contained the midecamycin 4"-propionyltransferase and could be used for microbial bioconversion of spiramycin into 4"-propionylspiramycin.
Insights
A stable mutant of S. mycarofaciens 1748, strain No. 68, was identified with smooth spores and a blockage in midecamycin biosynthesis. This mutant possesses midecamycin 4"-propionyltransferase, enabling microbial bioconversion of spiramycin.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Streptomyces mycarofaciens is a producer of macrolide antibiotics.
- Understanding biosynthetic pathways is crucial for antibiotic development and modification.
Purpose of the Study:
- To characterize a stable mutant (No. 68) of S. mycarofaciens 1748.
- To investigate the role of the mutant in the midecamycin biosynthetic pathway.
- To explore the potential of the mutant for microbial bioconversion.
Main Methods:
- High-temperature treatment of S. mycarofaciens 1748 spores to induce mutation.
- Electromicroscopic examination for morphological analysis.
- Physiological characterization including carbon source utilization and cultural properties.
- Feeding experiments to elucidate metabolic pathway blocks.
- Enzyme activity assays to determine specifictransferase presence.
Main Results:
- Mutant No. 68 exhibited smooth spores, unlike the thorny spores of the parent strain 1748, while maintaining similar spore chain morphology and cylindrical shape.
- Physiological tests revealed minor differences in carbon source utilization and cultural characteristics between the mutant and parent strains.
- Feeding experiments demonstrated that mutant No. 68 is blocked in macrolide lactone formation within the midecamycin biosynthetic pathway, suggesting a deficiency in polyketide synthase genes.
- Mutant No. 68 successfully converted spiramycin into 4"-propionylspiramycin, confirming the presence of midecamycin 4"-propionyltransferase.
Conclusions:
- Mutant No. 68 represents a stable strain with distinct spore surface morphology and a specific metabolic block in midecamycin biosynthesis.
- The identified block suggests a potential role for polyketide synthase genes in this pathway.
- The presence of midecamycin 4"-propionyltransferase in mutant No. 68 makes it a valuable tool for the microbial bioconversion of spiramycin into 4"-propionylspiramycin, a potentially useful derivative.