Streptomyces avermitilis from marine

The insecticidal strain 173 was isolated from marine source and its activity was explored by the bioassay of brine shrimp and Helicoverpa armigera . Based on morphological, physiological and molecular properties, the insecticidal strain 173 was identified as Streptomycetes avermitilis , which is the best insecticidal microorganism found in the terrestrial environment. The taxonomy of the strain 173, insecticidal spectrum and properties of the corresponding insecticidal antibiotics are reported.

Interrogation of Streptomyces avermitilis for efficient production of avermectins

The 2015 Nobel Prize in Physiology or Medicine has been awarded to avermectins and artemisinin,respectively.Avermectins produced by Streptomyces avermitilis are excellent anthelmintic and potential antibiotic agents.Because wild-type strains only produce low levels of avermectins,much research effort has focused on improvements in avermectin production to meet the ever increasing demand for such compounds.This review describes the strategies that have been widely employed and the future prospects of synthetic biology applications in avermectin yield improvement.With the help of genome sequencing of S.avermitilis and an understanding of the avermectin biosynthetic/regulatory pathways,synthetic and systems biotechnology approaches have been applied for precision engineering.We focus on the design and synthesis of biological chassis,parts,devices,and modules from diverse microbes to reconstruct and optimize their dynamic processes,as well as predict favorable effective overproduction of avermectins by a 4Ms strategy(Mine,Model,Manipulation,and Measurement).

乙基伊维菌素高产菌株选育及其发酵工艺优化

基因工程菌Streptomyces avermitilis AVE-H39产生的甲基和乙基伊维菌素(methyl and ethyl ivermectins),为新型高效低毒的阿维菌素(avermectin)衍生物,具有很好的开发应用前景。活性测试结果显示,乙基伊维菌素对朱砂叶螨Tetranychus cinnabarinus和松材线虫Bursaphelenchus xylophilus等农林作物害虫的活性优于甲基伊维菌素。鉴于菌株S.avermitilis AVE-H39的乙基伊维菌素产量低,制约了产业化开发,本研究经过多轮诱变选育,筛选获得了一株乙基伊维菌素发酵单位高的突变菌株,并通过Plackett-Burman试验设计及Box-Behnken设计-响应面法(response surface methodology,RSM)对该突变菌株的发酵培养基进行改良。经优化后的发酵条件为:玉米淀粉149.8 g/L,黄豆粉38.1 g/L,(NH_(4))_(2)SO_(4)3.04 g/L,甘露醇30.0 g/L,酵母抽提物20.0 g/L,CaCO_(3)3.0 g/L,CoCl_(2)0.01 mg/L,FeSO_(4)0.002 mg/L,转速220 r/min,pH 7.2,装液量30 mL/250 mL,接种量5%,发酵温度28℃。在此条件下,乙基伊维菌素的发酵效价达到最大值,为4965 mg/L。研究结果将为开发以乙基伊维菌素为主成分的新型十六元大环内酯农药奠定基础。

Influence of ^(12)C^(6+) ion irradiation on mutant avermitilis

The effects of 12C＋6 ion irradiation on colony morphology and mycelia morphology, as well as on mutation rate have been studied in the B1a high-product strains （ZJAV-Y1-203） mutated by heavy ion irradiation and compared with that in the original strain （ZJAV-A-1）. After irradiating the rate of a straw hat colony type having a high ability of producing B1a in ZJAV-Y1-203 strains was higher than that found in ZJAV-A-1 strains. When strains were cultured in a liquid medium for 24 hours, the mycelium becoming thinner could be observed in all of the irradiated ZJAV- Y1-203 groups, but only in the ZJAV-A-1 groups irradiated at the dose of 50 Gy or more. The early growth of mycelium was inhibited in the ZJAV- Y1-203 group irradiated with a high dose. The highest positive mutation rate （23.5%） of ZJAV - Y1 - 203 was reached at the lower dose of 30 Gy while the highest positive mutation rate of 34.2% in ZJAV-A-1 appeared at 50 Gy. These results indicate that the effects of heavy ion irradiation still exist even in the mutated Streptomyces avermitilis, and only the dose is lower and the effects not so strong compared with the one that is first irradiated with optimized heavy ion doses. This is evidence of the one directional mutation being controlled by many more factors in a organism.