筛选鉴定一株产生抑菌活性物质的海洋放线菌

目的：分离筛选能够产生抑菌活性物质的海洋放线茵,并进行生理生化和16SrDNA鉴定。方法：用分离培养基培养海洋放线菌,并筛选出能够产生抑菌活性物质的菌株,对所筛选菌株的形态特征、生理生化特性进行鉴定分析;采用通用引物27F、1492R扩增该菌株的16SrDNA,对测序结果进行分析;采用Neighbor—Joining（N—J）法构建系统发育进化树。结果：筛选到一株对金黄色葡萄球菌、大肠杆菌、白色念珠菌具有较强抗性的海洋放线菌F1,该菌株好氧,中度嗜盐,在高氏I号培养基上呈白色绒粉状,16SrDNA序列比对表明该菌株与田无链霉菌（Streptomyces tanashiensis）NR043369的相似度为99％。结论：筛选到的菌株F1是一株海洋来源的放线菌,与田无链霉菌NR043369的同源性较高,可能属海洋链霉菌属,对金黄色葡萄球菌等病原菌具有较强的抑菌活性。     

Salt‐enhanced cultivation as a morphology engineering tool for filamentous actinomycetes: Increased production of labyrinthopeptin A1 in Actinomadura namibiensis

Salt‐enhanced cultivation as a morphology engineering tool for the filamentous actinomycete Actinomadura namibiensis was evaluated in 500‐mL shaking flasks (working volume 100 mL) with the aim of increasing the concentration of the pharmaceutically interesting peptide labyrinthopeptin A1. Among the inorganic salts added to a complex production medium, the addition of (NH₄)₂SO₄ led to the highest amount of labyrinthopeptin A1 production. By using 50 mM (NH₄)₂SO₄, the labyrinthopeptin A1 concentration increased up to sevenfold compared to the non‐supplemented control, resulting in 325 mg L^?1 labyrinthopeptin A1 after 10 days of cultivation. The performance of other ammonium‐ and sulfate‐containing salts (e.g., NH₄Cl, K₂SO₄) was much lower than the performance of (NH₄)₂SO₄. A positive correlation between the uptake of glycerol as one of the main carbon sources and nongrowth‐associated labyrinthopeptin productivity was found. The change in the cell morphology of A. namibiensis in conjunction with increased osmolality by the addition of 50 mM (NH₄)₂SO₄, was quantified by image analysis. A. namibiensis always developed a heterogeneous morphology with pellets and loose mycelia present simultaneously. In contrast to the non‐supplemented control, the morphology of (NH₄)₂SO₄‐supplemented cultures was characterized by smaller and circular pellets that were more stable against disintegration in the stationary production phase.     

生防放线菌Ahn75的荧光标记及其在水稻中的定殖

【背景】目前gfp标记基因已成为研究靶标微生物与宿主之间互作的一种重要工具。利用gfp基因标记生防菌株,可以对生防菌株的生存及定殖能力进行有效追踪。【目的】对生防放线菌Ahn75进行荧光标记,探讨其在水稻中的定殖规律,为研究Ahn75的稻瘟病防治机制奠定基础。【方法】首先通过电激转化将含绿色荧光标记基因(gfp)的质粒pIJ8655导入大肠杆菌ET12567中,然后采用接合转移的方法将gfp整合到Ahn75基因组上;通过平板对峙试验检验Ahn75-GFP在标记绿色荧光后对稻瘟病病原菌的抑菌活性;采用喷施孢子液的方式将带荧光标记的Ahn75-GFP定殖水稻,并利用荧光显微镜观察生防菌在水稻中的定殖情况;对定殖水稻中的内生菌进行重分离,探究菌株在水稻组织中的分布规律。【结果】PCR扩增和荧光观察表明,绿色荧光标记基因成功整合到生防放线菌Ahn75中。通过平板对峙试验,发现Ahn75-GFP对稻瘟病病原菌抑菌活性与原始菌株没有显著差别。在荧光显微镜下,可以观察到Ahn75-GFP能稳定定殖于水稻的根、茎、叶等组织中,而水稻内生菌重分离试验表明该菌株在茎中的定殖力最强。【结论】获得一株绿色荧光标记生防菌株Ahn75-GFP,结果显示该菌株定殖水稻效果良好,这对于研究Ahn75的稻瘟病防治具有重要意义。     

不同微生物来源的加氧酶及其催化反应特征的研究进展

加氧酶作为一种氧化还原酶,可催化分子氧的氧原子与一大类有机化合物反应,被广泛应用于环保行业、美容保健行业、移植免疫过程、医药中间体的生产、资源开发利用、生态环境的生物修复、病虫害的防治等。本文综述了来源于真菌、细菌以及放线菌的加氧酶的研究进展,包括酶的性质、结构特点、催化机理及催化反应途径、应用等,并对微生物中加氧酶的研究前景进行了展望。     

放线菌制剂对人参生长及根域土壤微生物区系的影响

以小兴安岭地区人参为研究对象,探索放线菌制剂对人参的促生效应及对人参根区、根表土壤微生物区系的影响.结果表明： 经放线菌制剂Streptomyces pactum（Act12）处理后,人参药用部分产量增加,品质改善;叶片诱导酶活性提高,根系活力增强;土壤中细菌、放线菌的数量和比例显著增加,真菌的数量和比例减少.与对照相比,土壤微生物区系结构改变:优势菌荧光假单胞菌、韩国假单胞菌和氧化微杆菌在根区、根表土壤中的数量大幅提高;病原真菌烟色织孢霉在根区土壤中减少,在根表土壤中消失.表明施用放线菌制剂Act12能够改善土壤微生物区系,提高人参植株的抗性和根系活力,增加产量并改善品质.     

番茄内生菌St24的鉴定及其对灰霉病的生防作用

从番茄植株根茎部分离到1株有抑菌活性的植物内生放线菌菌株St24,对其分类地位以及对灰霉病菌的防治效果进行研究.结果表明: 菌株St24为酒红链霉菌.St24发酵液经石油醚萃取得到的粗提物对多种病原菌有抑制作用,其中对灰霉病菌的抑制作用最强,抑制菌丝生长的EC₅₀为11.78 mg·L^-1.粗提物处理灰霉菌后,菌丝量减少,菌丝体皱缩、断裂、原生质外渗,菌体细胞表面有许多瘤状畸形.处理后的灰霉病菌培养液在260 nm处比对照多出现一吸收峰,说明粗提物对病原菌的细胞膜透性有影响.经盆栽试验, St24发酵液对番茄灰霉病有保护和治疗的作用,100 mg·L^-1粗提物叶面喷雾的保护作用效果最好,24 h后防效达到94.3%,120 h后为85.4%.     

Germination and physiological properties of Frankia spores

Spores from four Frankia strains were isolated and purified to homogeneity. The purified spores were biochemically and physiologically characterized and compared to vegetative cells. Frankia spores exhibited low levels of endogenous respiration that were at least ten-fold lower than the endogenous respiration rate of vegetative cells. The macromolecular content of purified spores and vegetative cells differed. One striking difference among the Frankia spores was their total DNA content. From DAPI staining experiments, only 9% of strain ACN1^AG spore population contained DNA. With strains DC12 and EuI1c, 92% and 67% of their spore population contained DNA. The efficiency of spore germination was correlated to the percentage of the spore population containing DNA. These results suggest that the majority of strain ACN1^AG spores were immature or nonviable. The presence of a solidifying agent inhibited the initial stages of spore germination, but had no effect once the process had been initiated. The optimal incubation temperature for spore germination was 25°C and 30°C for strains DC12 and EuI1c, respectively. A mild heat shock increased the efficiency of spore germination, while root extracts also stimulated spore germination. These results suggest that strains DC12 and EuI1c may be suitable strains for further germination and genetic studies.     

土壤中聚乙烯降解菌的筛选、鉴定及降解特性

[目的] 农用地膜主要成分为聚乙烯（polyethylene,PE）,因其难以被降解,其废弃物常造成“白色污染”,本研究从常年覆盖农用地膜的土壤中筛选PE降解菌,并探究其对PE制品的降解效能。[方法] 采集的土壤样品用PE为唯一碳源的无机盐培养基进行富集,筛选、纯化PE降解菌,分离菌通过形态染色、生理生化特征、16S rRNA基因序列分析进行鉴定,检测其在不同PE浓度（0%、0.05%、0.10%、0.25%、0.50%、1.00%、2.00%、3.00%）的无机盐培养基中的生长曲线,最后通过扫描电镜、光镜观察,检测分离菌对农用地膜的降解效能。[结果] 从土壤中筛选获得一株能够降解PE的分离菌株（命名为SW1）,初步鉴定其为放线菌的诺卡氏菌属Nocardia sp.。SW1的生长对PE具有明显浓度依赖,在含2% PE的无机盐培养基中生长最快,在培养的第48 h菌液浓度开始明显增加,第60 h达到最大,而在不含PE的无机盐培养基中未见生长。形态生理学观察表明,35℃培养15 d后,扫描电镜观察可见有大量菌嵌入膜内或附于膜表面生长,膜表面粗糙,并开始出现破损;培养60 d后,光镜观察可见膜大面积破损,并出现空洞。[结论] 从土壤中筛选获得了一株能够有效降解PE制品的放线菌菌株Nocardia sp. SW1。该研究丰富了PE制品降解微生物的菌种资源,为PE塑料废弃物的生物降解提供了科学数据与参考。     

Antibiotic biosynthesis: from natural to unnatural compounds

The evolution of the field of biosynthesis from the unravelling of the mode of formation of natural products to the use of such knowledge to create new compounds is reviewed using examples from the author's laboratory. The discussion focuses on the mode of operation of type II (spore pigment PKS) and type I (rifamycin PKS) polyketide synthases and their diversion to generate unnatural products, and on the genetics and biochemistry of deoxysugar formation in granaticin biosynthesis as a prerequisite to combinatorial enzymatic synthesis of unusual glycosides. Journal of Industrial Microbiology & Biotechnology (2001) 27, 183–194. Received 21 September 1999/ Accepted in revised form 13 September 2000