灵芝孢子和抗性淀粉对糖尿病大鼠糖脂代谢及氧化应激的协同干预

目的：探讨灵芝孢子和抗性淀粉对Ⅱ型糖尿病大鼠糖脂代谢及氧化应激的作用和机制。方法：采用链脲佐菌素诱导的方法建立Ⅱ型糖尿病模型,考察灵芝孢子和抗性淀粉对糖尿病大鼠的血糖、血脂及氧化应激指标的影响。结果：抗性淀粉和灵芝孢子均可改善糖尿病大鼠血糖水平,对抗糖尿病引起的氧化应激损伤。抗性淀粉降血糖、抗氧化作用较强,灵芝孢子粉调节大鼠脂代谢紊乱效果明显,抗性淀粉和灵芝孢子协同作用可进一步改善脂代谢水平,增强二者抗氧化能力。结论：抗性淀粉和灵芝孢子粉协同干预模式和传送方式可有效降低糖尿病大鼠的血糖水平,改善脂代谢紊乱,提高抗氧化应激的能力,可作为一种较好的减缓糖尿病症状的有效饮食干预方法。     

β‐1,6‐glucan synthesis‐associated genes are required for proper spore wall formation in Saccharomyces cerevisiae

The yeast spore wall is an excellent model to study the assembly of an extracellular macromolecule structure. In the present study, mutants defective in β ‐1,6‐glucan synthesis, including kre1? , kre6? , kre9? and big1? , were sporulated to analyse the effect of β ‐1,6‐glucan defects on the spore wall. Except for kre6? , these mutant spores were sensitive to treatment with ether, suggesting that the mutations perturb the integrity of the spore wall. Morphologically, the mutant spores were indistinguishable from wild‐type spores. They lacked significant sporulation defects partly because the chitosan layer, which covers the glucan layer, compensated for the damage. The proof for this model was obtained from the effect of the additional deletion of CHS3 that resulted in the absence of the chitosan layer. Among the double mutants, the most severe spore wall deficiency was observed in big1? spores. The majority of the big1?chs3? mutants failed to form visible spores at a higher temperature. Given that the big1? mutation caused a failure to attach a GPI‐anchored reporter, Cwp2‐GFP, to the spore wall, β ‐1,6‐glucan is involved in tethering of GPI‐anchored proteins in the spore wall as well as in the vegetative cell wall. Thus, β ‐1,6‐glucan is required for proper organization of the spore wall. Copyright © 2017 John Wiley & Sons, Ltd.     

Cloning and heterologous expression of three type II PKS gene clusters from Streptomyces bottropensis

Mensacarcin is a potent cytotoxic agent isolated from Streptomyces bottropensis. It possesses a high content of oxygen atoms and two epoxide groups, and shows cytostatic and cytotoxic activity comparable to that of doxorubicin, a widely used drug for antitumor therapy. Another natural compound, rishirilide A, was also isolated from the fermentation broth of S. bottropensis. Screening a cosmid library of S. bottropensis with minimal PKS-gene-specific primers revealed the presence of three different type II polyketide synthase (PKS) gene clusters in this strain: the msn cluster (mensacarcin biosynthesis), the rsl cluster (rishirilide biosynthesis), and the mec cluster (putative spore pigment biosynthesis). Interestingly, luciferase-like oxygenases, which are very rare in Streptomyces species, are enriched in both the msn cluster and the rsl cluster. Three cosmids, cos2 (containing the major part of the msn cluster), cos3 (harboring the mec cluster), and cos4 (spanning probably the whole rsl cluster) were introduced into the general heterologous host Streptomyces albus by intergeneric conjugation. Expression of cos2 and cos4 in S. albus led to the production of didesmethylmensacarcin (DDMM, a precursor of mensacarcin) and the production of rishirilide A and B (a precursor of rishirilide A), respectively. However, no product was detected from the expression of cos3. In addition, based on the results of isotope-feeding experiments in S. bottropensis, a putative biosynthesis pathway for mensacarcin is proposed.     

牛栏山二锅头酒醅中芽孢杆菌分离鉴定及发酵风味分析

从牛栏山二锅头酒醅中分离筛选出5株产风味物质能力较好的芽孢杆菌,通过16SrDNA序列分析和构建系统发育树,5株细菌分别为地衣芽孢杆菌(Bacillus licheniformis)、蜡样芽孢杆菌(Bacillus cereus)、短小芽孢杆菌(Bacillus pumilus)和枯草芽孢杆菌(Bacillus subtilis)。分别对它们进行发酵风味分析,其发酵液经固相微萃取和GC-MS分析,并除去空白培养基中物质,地衣芽孢杆菌BL-1发酵液共检测得到14种风味物质,蜡样芽孢杆菌BC-1和短小芽孢杆菌BP-1发酵都得到12种风味物质,枯草芽孢杆菌BS-1好氧发酵共得到16种风味物质,枯草芽孢杆菌BS-2厌氧发酵共得到19种风味物质。除短小芽孢杆菌外,其他4株芽孢杆菌都含有较多数量的酯类化合物,且主要代谢风味物质都是3-羟基-2-丁酮,而短小芽孢杆菌BP-1则含有数量较多的烃类化合物,其主要风味物质是苯乙醇。     

灵芝孢子多糖提取工艺优化

采用响应面分析法对灵芝孢子多糖的提取工艺进行优化。考察3个变量(水料比、超声温度、微波时间)对灵芝孢子多糖提取率的影响,并通过响应面设计法确定灵芝孢子多糖提取技术的最佳工艺条件为水料比20∶1,超声提取时间为55 min,微波(200 W,60℃)提取时间20 min,在此条件下测得多糖的提取率为2.23%。     

蜡样芽胞杆菌生长特性及大蒜精油对其抑菌活性的研究

主要研究了37℃条件下3种蜡样芽胞杆菌在营养肉汤中的生长状况,建立了37℃下蜡样芽胞杆菌在营养肉汤中的Boltzmann牛长模犁,3条牛长曲线相关系数鼯均大于0．97;检测了不同培养时间蜡样芽胞杆菌的产芽胞情况,结果表明1号菌株和14号菌株较早产芽胞,培养相同时间,产芽胞数：1号菌株,4号菌株〉标准菌株;采用牛沣杯法和平板计数法研究了大蒜精油对蜡样芽胞杆菌的抑制效果,结果表明浓度为lO。的人蒜精油对3种蜡样芽胞杆菌都有很好的抑制效果,3种菌株中l号菌株最难抑制。     

5种农作物锈病孢子的扫描电镜观察

应用扫描电子显微镜观察小麦叶、蒜叶、蚕豆叶、玉米叶和葱叶上的锈病孢子形态特征,观察指标包括孢子的形状、孢子的表面特征以及孢壁纹饰等。结果表明孢子形状各异但以不规则椭圆状为多,孢子表面均具有刺和芽孔,孢壁呈光滑状、浅波状、皱波状和颗粒状纹饰。不同的孢子在形态上呈现一定的差异,通过形态的差异可以区分不同的孢子,为锈病病原体鉴别提供一定的依据。     

Antibacterial action on pathogenic bacterial spore by green tea catechins

Antibacterial effects of catechins, the major green tea polyphenols, were studied using Clostridium and Bacillus spores. Incubation with crude catechins decreased the number of C botulinum and C butyricum spores but not B cereus spores. Furthermore, the effects of six catechin derivatives on spores were investigated. (−)‐Epicatechin gallate (ECg), (−)‐epigallocatechin (EGC), (−)‐epigallocatechin gallate (EGCg) and (+)‐gallocatechin gallate (GCg) were more effective in decreasing C botulinum and C butyricum spore numbers than (+)‐catechin (C) and (−)‐epicatechin (EC). The vegetative growth of C botulinum and B cereus was inhibited by crude extracts of the catechins. Specifically, purified GCg and EGCg inhibited the vegetative growth of C botulinum and B cereus. The inhibitory effect of ECg on B cereus was similar to that of GCg. However, toxin‐production by B cereus was not inhibited by catechin. Damage to the membrane of C butyricum spores by catechin derivatives was shown using fluorescent microscopy. This study shows that low concentrations of catechins, although requiring a long exposure time, inhibited the growth of bacterial spores. However, the effects of the purified derivatives of the catechins were not the same and GCg and EGCg were found to be the most potent. Spores that are generally resistant to many disinfectants were sensitive to catechins. Copyright © 2005 Society of Chemical Industry