Fermentation media with different initial concentrations of ammonium and phosphate salts were used to study the inhibitory effects of those ions on growth and production of epothilone in Sorangium cellulosum and Myxoc...
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Fermentation media with different initial concentrations of ammonium and phosphate salts were used to study the inhibitory effects of those ions on growth and production of epothilone in Sorangium cellulosum and Myxococcus xanthus. The native epothilone producer, S. cellulosum was more sensitive to ammonium and phosphate than the heterologous producer, M. xanthus. An ammonium concentration of 12 mM reduced epothilone titers by 90% in S. cellulosum but by only 40% in M. xanthus. When 5 mM phosphate was added to the medium, production in both strains was 60% lower. Higher phosphate concentrations had little additional effect on M. xanthus titers, but epothilone production with 17 mM extra-cellular phosphate in S. cellulosum was 95% lower than in the control condition. The effect of iron supplementation to the fermentation medium was also investigated. Both strains showed best production with 20,muM iron added to the medium.
Cystobacter species strain CK 1 does not grow with more than 0.2 microgram/ml acriflavine. Spontaneous two-step mutants growing with 2 microgram acriflavine per ml have been selected. One mutant (strain CK3) was used ...
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Cystobacter species strain CK 1 does not grow with more than 0.2 microgram/ml acriflavine. Spontaneous two-step mutants growing with 2 microgram acriflavine per ml have been selected. One mutant (strain CK3) was used to investigate the effect of repair inhibitors. Both strains exhibit pronounced shoulders in their UV dose curves of inactivation. Acriflavine (AF), coumarin (CU), and caffeine (CA) when incorporated in the post-irradiation plating medium decreased survival of irradiated cells. Post-treatment with 2 microgram acriflavine/ml abolished the shoulder of the curve. Caffeine (1600 microgram/ml) and coumarin (350 microgram/ml) reduced it only to about 40%. It is concluded that probably two repair mechanisms are present. Pre-treatment of the cells with 2 microgram acriflavine/ml for two hours before UV-irradiation resulted in a constant dose enhancement factor of 1.9. The protective effect is increased with the time of treatment with acriflavine. This may indicate that pyrimidine dimers are responsible for UV-inactivation.
Fulvocin C is a bacteriocin from M. fulvus Mx f16. It has a MW of 4672 and is one of the smallest bacteriocins known. Four disulfide bonds give the molecule a tight structure, so that its native form was not attacked ...
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Fulvocin C is a bacteriocin from M. fulvus Mx f16. It has a MW of 4672 and is one of the smallest bacteriocins known. Four disulfide bonds give the molecule a tight structure, so that its native form was not attacked by chymotrypsin or Pronase. Fulvocin C was stable in various organic solvents and could tolerate ***. C in aqueous solution without loss of activity. The killing effect of fulvocin C was observed only at concentrations higher than 0.25 .***/l. Macromolecular synthesis (DNA, RNA, protein) was affected very gradually. Viability in growing cultures decreased slowly from 100-25% during 1 generation (8 h). Cell division was affected early. After 1 generation v-shaped cell pairs had accumulated in the culture. Electron micrographs revealed extended membrane systems connected with the inner membrane. The most striking effect was that often the outer membranes of neighboring cells seemed to have fused laterally. With further incubation many cells lost their rod shape and empty bags became predominant.
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