We isolated naturally occurring actinomycetes with an ability to produce metabolites having antifungal property against, Colletotrichum gloeosporioides, the causal agent of mango anthracnose. One promising strain was ...We isolated naturally occurring actinomycetes with an ability to produce metabolites having antifungal property against, Colletotrichum gloeosporioides, the causal agent of mango anthracnose. One promising strain was strong antifungal activity, was selected for further studies. Based on the physiological and biochemical characteristics, the bacterial strain was identical to Streptomyces aureofaciens. Culture filtrate collected from the exponential and stationary phases inhibited the growth of fungus tested, indicating that growth suppression was due to extracellular antifungal metabolites present in culture filtrate. Isolate highly produced extracellular chitinase and β-1,3-glucanase during the exponential and late exponential phases, respectively. In order to standardize the metabolite production some cultural conditions like different incubation time in hours, pH, carbon sources and concentrations and nitrogen source were determined. During fermentation, growth, pH and hydrolysis enzymes production were monitored .Treatment with bioactive components exhibited a significantly high protective activity against development of anthracnose disease on mango trees and increased fruit yield.展开更多
Demecycline(DMTC)and demeclocycline(DMCTC)are C6-demethylated derivatives of tetracycline(TC)and chlortetracycline(CTC),respectively.They are precursors of minocycline and tigecycline,which showed remarkable bioactivi...Demecycline(DMTC)and demeclocycline(DMCTC)are C6-demethylated derivatives of tetracycline(TC)and chlortetracycline(CTC),respectively.They are precursors of minocycline and tigecycline,which showed remarkable bioactivity against TC-resistant bacteria and have been used clinically for decades.In order to biosynthesize drug precursors DMTC and DMCTC,the function of a possible C-methyltransferase encoding gene ctcK was studied systematically in the CTC high-yielding industrial strain Streptomyces aureofaciens F3.TheΔctcK mutant accumulated two new products,which were turned out to be DMTC and DMCTC.Meanwhile,timecourse analysis of the fermentation products detected the epimers of DMTC and DMCTC transformed spontaneously.Finally,an engineering strain with higher productivity of DMCTC was constructed by deleting ctcK and overexpressing ctcP of three extra copies simultaneously.Construction of these two engineering strains not only served as a successful example of synthesizing required products through metabolic engineering,but also provided original strains for following elaborate engineering to synthesize more effective tetracycline derivatives.展开更多
文摘We isolated naturally occurring actinomycetes with an ability to produce metabolites having antifungal property against, Colletotrichum gloeosporioides, the causal agent of mango anthracnose. One promising strain was strong antifungal activity, was selected for further studies. Based on the physiological and biochemical characteristics, the bacterial strain was identical to Streptomyces aureofaciens. Culture filtrate collected from the exponential and stationary phases inhibited the growth of fungus tested, indicating that growth suppression was due to extracellular antifungal metabolites present in culture filtrate. Isolate highly produced extracellular chitinase and β-1,3-glucanase during the exponential and late exponential phases, respectively. In order to standardize the metabolite production some cultural conditions like different incubation time in hours, pH, carbon sources and concentrations and nitrogen source were determined. During fermentation, growth, pH and hydrolysis enzymes production were monitored .Treatment with bioactive components exhibited a significantly high protective activity against development of anthracnose disease on mango trees and increased fruit yield.
基金This work was supported by grants from National Key R&D Program of China(2018YFA0900400)from the Ministry of Science and Technologythe National Natural Science Foundation of China(31630002,31770038,31700029,and 21661140002)+1 种基金Shanghai Pujiang Program from the Shanghai Municipal Council of Science and Technology(12PJD021)and China Postdoctoral Science Foundation(2017M620151).
文摘Demecycline(DMTC)and demeclocycline(DMCTC)are C6-demethylated derivatives of tetracycline(TC)and chlortetracycline(CTC),respectively.They are precursors of minocycline and tigecycline,which showed remarkable bioactivity against TC-resistant bacteria and have been used clinically for decades.In order to biosynthesize drug precursors DMTC and DMCTC,the function of a possible C-methyltransferase encoding gene ctcK was studied systematically in the CTC high-yielding industrial strain Streptomyces aureofaciens F3.TheΔctcK mutant accumulated two new products,which were turned out to be DMTC and DMCTC.Meanwhile,timecourse analysis of the fermentation products detected the epimers of DMTC and DMCTC transformed spontaneously.Finally,an engineering strain with higher productivity of DMCTC was constructed by deleting ctcK and overexpressing ctcP of three extra copies simultaneously.Construction of these two engineering strains not only served as a successful example of synthesizing required products through metabolic engineering,but also provided original strains for following elaborate engineering to synthesize more effective tetracycline derivatives.
