除虫链霉菌10个聚酮类抗生素生物合成基因簇的敲除对阿维菌素产量的影响

【目的】考察除虫链霉菌基因组中其它聚酮合成酶类(Polyketide synthase,PKS)抗生素生物合成基因簇的敲除突变对于阿维菌素产量的影响。【方法】构建了11个PKS基因簇的打靶Cosmid和质粒载体,导入除虫链霉菌中筛选突变株。【结果】在工业菌株MMR630中成功敲除了10个PKS基因簇。发酵结果显示7个PKS基因簇敲除突变株中阿维菌素的产量均有不同程度的提高,而2个突变株不能产生阿维菌素。然而,在3个连续敲除2个PKS基因簇的突变株中阿维菌素产量没有能够超过单个PKS敲除突变株的提升幅度。【结论】除虫链霉菌基因组的一些PKS基因簇的敲除可以提高阿维菌素的产量,同时暗示同一类次生代谢产物的代谢流之间存在复杂的相互作用关系。     

Biocatalytic synthesis and in vitro release of biodegradable linear polyesters with pendant ketoprofen

Enzyme-catalyzed polycondensation for the synthesis of polyester prodrugs of ketoprofen was reported. Lipase acrylic resin from Candida antarctica (CAL-B) was used to synthesize the linear polyesters with pendent ketoprofen groups based on ketoprofen glycerol ester, poly(ethylene glycol), and divinyl sebacate. The products were characterized by GPC and (1)H NMR. The results indicated that the molecular weight and yields of the polyesters depend on experimental conditions such as temperature and feed ratio. The in vitro study showed that the drug release from the polyester was slow under physiological conditions, which indicated that the polyester could be a promising prodrug with extended pharmacological effects by delayed release of ketoprofen.     

Four new compounds from the leaves of Acer truncatum

Four new compounds, 3-(4-hydroxy-3,5-dimethoxyphenyl)propyl formate (1), 2,6-dimethoxy-4-[(1S)-3-methoxypropyl]phenol (2), (1R,2R)-4-[(3R)-3-hydroxybutyl]-3,3,5-trimethylcyclohex-4-ene-1,2-diol (3), and (1S,3R,3aR,6S,7S,9aR)-decahydro-1-(hydroxymethyl)-1,7-dimethyl-3a,7-methano-3aH-cyclopentacyclooctene (4) were isolated from the leaves of Acer truncatum, together with twelve known compounds. Their structures were elucidated on the basis of extensive spectroscopic techniques. The absolute configuration of compound 3 was established by the modified Mosher's method. All compounds were evaluated for antibacterial activities.     

Five new steroidal compounds from Ypsilandra thibetica

Five new steroids, including the four new steroidal saponins ypsilandroside B (1), ypsilandroside A (2), isoypsilandroside A (4), and isoypsilandroside B (5), as well as the new steroidal sapogenin isoypsilandrogenin (3), were isolated from the whole plant of Ypsilandra thibetica Franch. Their structures were determined on the basis of spectroscopic analyses, including extensive 2D-NMR techniques. The structure and relative configuration of ypsilandroside B (=(3beta,12alpha,25R)-3-[(alpha-L-rhamnopyranosyl-(1-->2)-beta-D-apiofuranosyl)oxy]spirost-5-ene-12,27-diol; 1) was unequivocally determined by single-crystal X-ray diffraction. The antifungal and antibacterial activities of 1-5 towards various types of fungi and bacteria are reported.     

Tree species influences soil microbial community diversity but not biomass in a karst forest in southwestern China

中国西南喀斯特森林树种对土壤微生物群落多样性和生物量的影响陆地生态系统中植物种对土壤微生物群落结构的影响不一,而喀斯特生态系统中植物种对土壤微生物群落结构影响的研究尚未见报道。本研究利用磷酸脂肪酸(PLFA)法,分析了黔中高原型喀斯特常绿落叶阔叶混交林5个优势树种—窄叶石栎(Lithocarpus confinis Huang)、圆果化香(Platycarya longipes Wu)、滇鼠刺(Itea yunnanensis Franch.)、安顺润楠(Machilus cavaleriei H. Lév.)、云贵鹅耳枥(Carpinus pubescens Burkill)—与土壤理化性质对土壤微生物群落组成和生物量的影响。在测试的212个土壤样品 中共检测出132种PLFA,每个样品土壤微生物平均PLFA数量和生物量分别为65.97和11.22 µg g^–1。土壤表层(0–10 cm)的土壤微生物PLFA数量与下层(10–20 cm)土壤接近,但前者土壤微生物生物量显著高于后者(P < 0.05)。树种影响土壤微生物PLFA数量,但对土壤微生物生物量没有影响。云贵鹅耳枥附近的土壤微生物PLFA数量显著高于其他树种(P < 0.05),而其他树种土壤微生物PLFA数量接近。土壤微生物 生物量与表层土壤的理化性质无显著相关,但与下层土壤的有机碳、全氮和全磷含量呈显著正相关 (P < 0.05)。总之,黔中高原型喀斯特森林真菌/细菌生物量比率低,微生物总生物量低,但微生物群落多样性高。树种对土壤微生物群落多样性产生影响。     

种群密度与施肥对垂穗披碱草刈割后补偿作用的影响

 以甘南亚高山草甸常见牧草垂穗披碱草(Elymus nutans)为对象,通过考察种群密度、施肥与刈割处理等对植物生长和生殖的影响效应,比较了垂穗披碱草在5个密度及2个施肥实验处理条件下对4种刈割处理的补偿性反应特点。结果表明,在所有密度及施肥处理条件下,早期轻度刈割处理 (分蘖期刈割,留茬4 cm) 都有利于植物的补偿作用,后期重度处理 (拔节期刈割,留茬2 cm) 可显著降低植物的地上部分生物量及生殖部分干重 (穗重)。在不施肥情况下,刈割对垂穗披碱草的影响程度随种群密度而加大,在低密度处理中早期轻度刈割的植物发生了超补偿。可以认为,低密度种群中植物具有较多的分蘖是植物在刈割后表现出较高补偿能力的一个重要生物学原因。实验还发现,施肥可提高植物个体的分蘖能力和秆叶再生能力,因而总体上可增强植物的补偿能力,并且在中等密度条件下垂穗披碱草的补偿能力较强,尽管没有发生超补偿现象。不过,施肥主要是有利于植物地上营养器官的补偿,生殖器官的补偿程度较小一些。试验结果对科学管理人工草场具有一定的指导意义。     

白星花金龟聚集信息素的分离鉴定及引诱效果

[目的]明确白星花金龟Protaetia brevitarsis Lewis聚集信息素的有效成分,为白星花金龟的绿色防控提供支持.[方法]通过动态顶空法收集白星花金龟雌虫、雄虫和雌雄虫混合挥发物,用气相色谱-质谱(Gas chromatography-mass spectrometry,GC-MS)联用技术对收集的挥发物进行分析鉴定,并利用触角电位(Electroantennogram,EAG)仪和Y型嗅觉仪测定白星花金龟对8种化合物的触角电位和行为选择反应.[结果]白星花金龟雌虫、雄虫和雌雄虫混合挥发物中皆鉴定出8类15种化合物,包括6种烷烃类、2种酚类、2种芳香烃类、1种烯类、1种吡啶类、1种胺类、1种醇类和1种酮类.EAG试验结果表明,白星花金龟对8种化合物都有EAG反应,且不同挥发物间、同种挥发物不同浓度间的EAG反应存在差异.白星花金龟对蒎烷胺、3,4-二甲基-6-乙基苯酚、2,3-二甲基苯乙酮和2,6,10,14-四甲基十七烷4种挥发物的EAG反应相对值在1μg/μtL时达到最大,对萘、苯并噻唑、百里酚和正十四烷4种挥发物的EAG反应相对值在10 μtg/μtL时达到最大.行为选择反应表明,白星花金龟雌成虫、雄成虫对2,3-二甲基苯乙酮有明显趋向性,选择反应率大于70％,对2,6,10,14-四甲基十七烷、萘、苯并噻唑、百里酚和正十四烷5种物质均表现出显著或极显著的驱避效果,对3,4-二甲基-6-乙基苯酚和蒎烷胺表现出了性别上的差异,雄虫对3,4-二甲基-6-乙基苯酚表现出显著的趋向性,对蒎烷胺表现出显著的驱避性,而雌虫对这2种挥发物却无明显反应.[结论]2,3-二甲基苯乙酮对白星花金龟雌成虫、雄成虫有明显的引诱效果,2,6,10,14-四甲基十七烷、萘、苯并噻唑、正十四烷和百里酚有较强的驱避作用,推测2,3-二甲基苯乙酮是白星花金龟聚集信息素的有效组分.     

Seasonality of insect succession on exposed rabbit carrion in Guangzhou, China

Abstract  Succession patterns for insect fauna, spanning four seasons, on rabbit carcasses were studied in Guangzhou China from 2006 to 2008. A total of 49 taxa belonging to three orders and 15 families were collected and identified. Four decomposition stages were recognized: fresh, bloated, decay and dry stage. Taxa diversity was higher in bloated and decay stages than fresh and dry stages. Internal and ambient temperatures were measured. Maximum internal temperature arrived earlier in warmer seasons. The sequence of insect succession in this study follows the same general patterns: the Diptera peaked initially, and the Coleoptera peaked later. Chrysomya megacephala was the dominant species in four seasons. Its time point of different development stages on carrion could be the most important indicators for PMI (postmortem interval) estimation in Guangzhou. Yearly and seasonal differences in activities of insects were compared. Alpha diversity indices were calculated. There were no significant differences in Shannon-Wiener index, evenness ( J ) and dominance ( C ) between seasons and years. From the Jaccard similarity index, the highest similarity was between winter and spring, while the lowest was between summer and winter. Some species occurring exclusively in one season may be important to characterize different seasons. A list of the insect taxa associated with above-ground rabbit carrion during the four seasons was compiled, which can be used for estimating time since death in similar bio-climate areas.