氮源对利迪链菌素生产及相关次级代谢物分布的影响

The effects of nitrogen sources on streptolydigin production and distribution of secondary metabolites were investigated for flask cultured S.lydicus AS 4.2501.When peptone,asparamide,and glutamic acid were ex- amined as the nitrogen source,respectively,liquid chromatography-mass spectrometry（LC-MS）and photodiode array（PDA）analyses revealed the formation of two analogues of streptolydigin in the fermentation broth.When soybean meal was used as the source of nitrogen,three analogues of streptolydigin were detected.The use of am- monium sulfate as a source of nitrogen resulted in a lower pH value of the fermentation system,thus inhibiting streptolydigin biosynthesis and changing the metabolic profiling.Among the nitrogen sources that were made use of,glutamic acid was most favorable to the formation of streptolydigin.Simultaneously,this study also showed that the changing nitrogen sources resulted in altering the production and relative ratios of streptolydigin and its analogues.     

Structural Analysis of Cytochrome P450 105N1 Involved in the Biosynthesis of the Zincophore, Coelibactin

Coelibactin is a putative non-ribosomally synthesized peptide with predicted zincophore activity and which has been implicated in antibiotic regulation in Streptomyces coelicolor A3(2). The coelibactin biosynthetic pathway contains a stereo- and regio-specific monooxygenation step catalyzed by a cytochrome P450 enzyme (CYP105N1). We have determined the X-ray crystal structure of CYP105N1 at 2.9 Å and analyzed it in the context of the bacterial CYP105 family as a whole. The crystal structure reveals a channel between the α-helical domain and the β-sheet domain exposing the heme pocket and the long helix I to the solvent. This wide-open conformation of CYP105N1 may be related to the bulky substrate coelibactin. The ligand-free CYP105N1 structure has enough room in the substrate access channel to allow the coelibactin to enter into the active site. Analysis of typical siderophore ligands suggests that CYP105N1 may produce derivatives of coelibactin, which would then be able to chelate the zinc divalent cation.     

ε-聚赖氨酸产生菌的筛选

改进了筛选ε-聚赖氨酸产生菌的方法。在加有复合抑菌剂的初筛平板上涂布土壤悬液,于28℃培养7 d后喷洒次甲基兰溶液显色,挑出周围形成透明圈的菌落,再次接种培养,7d后挖取菌落周围的琼脂块,利用文中设计的简易转移装置,将琼脂块中的水溶性成分转移到滤纸上,然后分别用茚三酮试剂和Dragendorff试剂检测,挑取对2种试剂都呈阳性的菌落,进一步摇瓶复筛,发现1株放线菌的发酵液中有ε-聚赖氨酸。经生化反应鉴定和分子生物学鉴定,确定该菌株为灰橙链霉菌(Streptomyces griseoaurantiacus)。     

海洋链霉菌M259高产蓝色素理化性质研究

在青岛胶州湾沿海采集样品,对样品进行分离、纯化后获得300株海洋链霉菌,从中检测到一株高产蓝色素的海洋链霉菌M259。本文主要探讨该菌产生的蓝色素的理化性质,研究发现该蓝色素对八株受试菌无抑菌活性,在590nm处有最大吸收峰,水溶性好,光热稳定性强,而且具有耐糖、耐还原性,酸性条件下为红色,碱性条件下为蓝色,对大部分金属离子和食品添加剂稳定,经急性毒理实验证实为实际无毒物质。     

原生质体融合提高产谷氨酰胺转氨酶菌株产量

目的：研究并建立产谷氨酰胺转氨酶茂原链霉菌原生质体制备技术,通过原生质体融合技术筛选高产菌株。方法：以溶菌酶处理茂原链霉菌获得原生质体,采用原生质体融合技术,通过96 孔板高通量初筛、试管复筛、摇瓶验证选育高产菌株。结果：茂原链霉菌形成的原生质体再生出的菌落直径比较小,而菌丝生成的菌落直径比较大,两种形态的菌落96 孔板发酵后酶活力有显著性差异。不同的茂原链霉菌株制备原生质体,酶解程度、原生质体纯度、再生率有很大的差异,再生率最高可达1 804.25%,最低仅为12.76%。原生质融合后的高产菌株,选取96 孔板初筛酶活力前3%的菌株进行试管发酵,得到高产菌株比例为32.2%,酶活力比亲本高22.4%,经摇瓶验证产酶比对照提高16.28%。结论：利用基因组重排技术,可以初步对茂原链霉菌进行高产菌株选育。     

Actinomycetes in relation to taste and odour in drinking water: myths, tenets and truths

Actinomycetes are a complex group of bacteria present in a wide variety of environments, either as dormant spores or actively growing. Some actinomycetes produce two potent terpenoids (geosmin and 2-methylisoborneol (MIB)) and pyrazines, common causes of drinking water off flavours, and have been implicated in taste and odour episodes. However, isolation from a water source is not evidence that actinomycetes caused a taste and odour event. Dormant spores of actinomycetes may be isolated from aquatic environments in high concentrations, despite production in the terrestrial environment. Similarly, odourous compounds produced by actinomycetes may be produced terrestrially and washed into aquatic environments, with or without the actinomycetes that produced them. Actinomycetes may exist as actively growing mycelium in small, specialized habitats within an aquatic system, but their odourous compounds may influence a wider area. This paper attempts to elucidate the types and activities of actinomycetes that may be found in, or interact with, drinking water supplies.     

L-缬氨酸对Streptomyces natalensis HW-2合成纳他霉素的影响

以Streptomyces natalensis HW-2为研究对象,考察了添加L-缬氨酸对纳他霉素生物合成途径的影响。结果表明:在纳他霉素发酵至36 h时添加0.5 g/L L-缬氨酸,纳他霉素产量达到1.83 g/L,比对照组提高了84.85%。添加L-缬氨酸后引起菌体生物量降低和pH升高,而葡萄糖利用速率加快;胞内丙酮酸激酶(PK)、磷酸烯醇式丙酮酸羧化酶(PEPC)和丙酮酸羧化酶(PC)活性增强,柠檬酸合酶(CS)活力降低了26.57%;发酵液中丙酮酸(色谱法)、草酰乙酸(色谱法)和乙酰辅酶A(分光光度法)的含量分别提高了80.50%、53.28%和47.19%,乙酸(色谱法)、丙酸(色谱法)和α-酮戊二酸(色谱法)的含量分别提高了16.98%、10.65%和15.40%,而柠檬酸(色谱法)的含量降低了27.01%。     

Optimization of cultivation conditions for fungichromin production from Streptomyces padanus PMS-702

A novel strain, Streptomyces padanus PMS-702, was employed to produce fungichromin (FC, a polyene macrolide antibiotic) in a shake flask cultivation. In comparing the effects of various carbon and nitrogen sources on PMS-702 cultivation, it was found that glucose and soybean meal medium yielded the highest FC within 2 days. Factors such as medium composition, cultivation temperatures, and initial pH were optimized for FC production with response surface methodology (RSM). The optimal cultural condition obtained is as follows: glucose 11.2 g/L, soybean meal 11.2 g/L, CaCO₃ 0.46 g/L, temperature 31.7 °C, and an initial pH 5.5. Under these conditions, FC production reached 112 mg/L, about an increase of 2.86 times, as compared to results under basic conditions.     

Effect of a global regulatory gene, afsR2, from Streptomyces lividans on avermectin production in Streptomyces avermitilis

The global regulatory gene, afsR2, from Streptomyces lividans was previously reported to highly stimulate two structurally unrelated antibiotics, actinorhodin and undecylprodigiosin, in both S. lividans and its close relative S. coelicolor. Production of eight avermectin components was also improved in S. avermitilis: the use of wild-type S. avermitilis and its high-producing mutant, transformed by introduction of multiple copies of afsR2, increased the total avermectin productions by 2.3-fold and 1.5-fold, respectively.     

Biosynthesis of the Fluorinated Natural Product Nucleocidin in Streptomyces calvus Is Dependent on the bldA‐Specified Leu‐tRNAUUA Molecule

Nucleocidin is one of the very few natural products known to contain fluorine. Mysteriously, the nucleocidin producer Streptomyces calvus ATCC 13382 has not been observed to synthesize the compound since its discovery in 1956. Here, we report that complementation of S. calvus ATCC 13382 with a functional bldA‐encoded Leu‐tRNA^UUA molecule restores the production of nucleocidin. Nucleocidin was detected in culture extracts by ¹⁹F NMR spectroscopy, HPLC‐ESI‐MS, and HPLC‐continuum source molecular absorption spectroscopy for fluorine‐specific detection. The molecule was purified from a large‐scale culture and definitively characterized by NMR spectroscopy and high‐resolution MS. The nucleocidin biosynthetic gene cluster was identified by the presence of genes encoding the 5′‐O‐sulfamate moiety and confirmed by gene disruption. Two of the genes within the nucleocidin biosynthetic gene cluster contain TTA codons, thus explaining the dependence on bldA and resolving a 60‐year‐old mystery.