草地早熟禾根际固氮菌的生物效能

利用乙炔还原法、比色法等对草地早熟禾(Poa pratensis)根际分离得到的21个固氮菌株进行固氮酶活性、溶磷能力和分泌植物生长素性能的研究测定,在固氮酶活性测定中,21个菌株还原C2H2产生的C2H4在39.9～227.5 nmol·mL-1·h-1,大于100 nmol·mL-1·h-1的有14株,占所分离固氮菌株的67%;菌株的溶磷强度在13.38～58.21 μg·mL-1,其中菌株N4 、N16及N20溶磷能力较强;菌株N2、N4、N5、N10、N14、N16、N17及N20具有较强的分泌植物生长激素的能力。     

无乳链球菌研究进展

VII型分泌系统存在于无乳链球菌 (Streptococcus agalactiae) 中,其组成膜蛋白对底物蛋白的分泌转运至关重要。为此利用热敏型自杀质粒,构建了含氯霉素筛选标签的膜蛋白重组敲除载体pSET4s-ΔessA、pSET4s-ΔessB、pSET4s-ΔessC,经同源重组后,利用PCR技术筛选到了其缺失突变株-无乳链球菌ΔessA、ΔessB、ΔessC。通过菌株生长曲线分析,ΔessA、ΔessB、ΔessC敲除株均较野生株 (WT) 生长过程变慢,其中ΔessA、ΔessB敲除株在生长早期有显著性差异 (P<0.01)。对ESAT6蛋白分泌影响分析显示,与WT株相比,ΔessA、ΔessB、ΔessC敲除株ESAT6的表达量均显著下调 (P<0.01)。结果显示,ΔessA、ΔessB、ΔessC敲除株均较WT株毒力显著降低 (P<0.01)。研究表明,essA、essB、essC为无乳链球菌VII型分泌系统重要的膜蛋白,其基因缺失造成了分泌蛋白ESAT6 mRNA表达水平下降,影响了菌株毒力。     

外源磷输入对底泥砷污染香蒲根系分泌烃类物质的影响

为探究不同外源磷输入对底泥砷污染香蒲根系分泌烃类物质的影响,采用室内土壤模拟试验,测定砷污染底泥条件下,不同外源磷输入对香蒲根系烃类物质种类和浓度的影响。结果表明：外源磷输入显著促进底泥砷污染生境中香蒲根系分泌烃类物质种类和浓度增加;香蒲根系分泌共有烃类物质以简单的链状正构烷烃为主,而特有烃类物质则以链状支链烷烃为主。砷污染底泥高浓度外源磷输入对烃类物质浓度影响最为显著;烃类物质种类和浓度与植物根系砷富集浓度和根系耐性指数呈显著性正相关关系。     

Effects of aerobic conditions in the rhizosphere of rice on the dynamics and availability of phosphorus in a flooded soil – A model experiment

The secretion of O₂ by rice roots results in aerobic conditions in the rhizoshere compared to the bulk flooded soil. The effect of this phenomenon on the adsorption/desorption behavior and on the availability of phosphorus (P) in a flooded soil was investigated in a model experiment. An experimental set‐up was developed that imitates both O₂ release and P uptake by the rice root. The results showed that O₂ secretion significantly reduced P adsorption/retention and increased P desorption/release in the “rhizosphere” soil, compared to the anaerobic bulk soil. The P uptake by an anion exchange resin from both unfertilized and P‐amended soil was significantly increased. The results confirm that the O₂ secretion is an important mechanism to enhance P availability and P uptake of rice under flooded conditions, where the “physico‐chemical” availability of P in the anaerobic bulk soil is strongly reduced. The decrease of P availability in the P‐amended flooded bulk soil was mainly associated with the almost complete transformation of the precedingly enriched Al‐P fraction into Fe‐bound P with extremely low desorption/release characteristics during the subsequent flooding.     

黑曲霉糖化酶基因在毕赤酵母X33中的高效表达

为高效表达黑曲霉糖化酶基因,根据GenBank中糖化酶的氨基酸序列(登录号:AY652617),选用毕赤酵母(Pichia pastoris)密码子偏嗜性,全基因合成新的cDNA序列。改造后的基因克隆到pGAPZαA质粒中,获得重组分泌型酵母表达质粒pGAPZαA-EC,经限制性内切酶Bln Ⅰ酶切线性化后,电击转化入毕赤酵母细胞X33内。经高浓度博莱霉素抗性筛选,得到高拷贝转化子,PCR检测结果显示,糖化酶基因与毕赤酵母染色体稳定结合。糖化酶蛋白获得分泌表达,SDS-PAGE分析其分子质量约为80 ku,其表达量约为180 mg/L。表达产物经Starch-PAGE活性染色,显示其具有酶学活性。     

影响老瓜头泌蜜量主导因素的研究

老瓜头自然分布于沙漠地带。在老瓜头开花期,天气变化无常。我们研究了对老瓜头泌蜜量起关键影响作用的气象因子。根据当地气候的变化规律进行预测预报,指导养蜂者正确选择场地,以夺取老瓜头蜜高产。     

侧孢芽孢杆菌2-Q-9外泌抑菌物质性质

侧孢芽孢杆菌(Bacillus laterosporus)菌株2-Q-9分泌的抑菌物质能强烈抑制青枯病菌的3个生理小种的正常生长.为了进一步在生产上利用该抑菌物质,就该抑菌物质的性质进行了初步研究.结果表明,该抑菌物质经高温处理后性质稳定;在碱性条件下比酸性条件下稳定;对胰蛋白酶和蛋白酶K不敏感,对胃蛋白酶部分敏感;该抑菌物质可能为蛋白或多肽类物质.     

水稻白叶枯病菌hrcU基因缺失突变体构建及功能研究

 通过基因敲除方式,构建了水稻白叶枯病菌hrcU基因的缺失突变体。突变体丧失了在水稻上的致病性和在非寄主植物上的过敏反应。携带hrcU基因的黏粒完全互补了hrcU突变菌株的表型,互补菌在水稻组织中的生长能力也与野生型菌株相当。免疫杂交结果显示,hrcU基因突变后,水稻白叶枯病菌的Harpin蛋白Hpa1不能从细胞内分泌到胞外。这些结果表明,水稻白叶枯病菌hrcU基因的主要功能是形成Ⅲ型分泌系统,将效应分子分泌到病原细菌胞外,从而决定了在非寄主上的过敏反应和在水稻上的致病性。     

泌乳母猪乳腺对乳汁前体物的摄取及其乳汁成分的分泌

乳汁产量和营养成分在很大程度上决定哺乳期仔猪的生长性能,但由泌乳期第 ８天至断奶,乳腺不能合成足量乳汁以支持仔猪最大生长潜力的发挥。因此,有必要弄清泌乳母猪乳腺对乳汁前体物的摄取及乳汁成分分泌的这种“进—出”生化代谢规律,以便利用营养措施调控乳汁成分。本文阐述了乳腺对乳汁前体物质,如葡萄糖、脂肪酸、氨基酸、矿物质、维生素的摄取及其乳汁成分的分泌,并讨论了调控“摄取—分泌”这个过程中的潜在生化机制。     

Chemerin analog regulates energy metabolism in sheep

Accumulating data suggest a relationship between chemerin and energy metabolism. Our group previously described gene cloning, expression analysis and the regulatory mechanism of chemerin and its own receptor in mice and cattle. The objective of the present study was to investigate the physiological effect of chemerin on endocrine changes and energy metabolism in sheep using a biologically stable chemerin analog. The chemerin analog was intravenously administrated (100 or 500 µg/head) to sheep, and plasma insulin and metabolites (glucose, nonesterified fatty acids (NEFA), triglyceride, total cholesterol and high‐density lipoprotein (HDL) cholesterol) were analyzed. The chemerin analog dramatically increased the insulin levels, and glucose levels were decreased. NEFA levels were slightly decreased at 20 min but then increased gradually from 60 to 180 min after analog administration. In addition, injection of the chemerin analog immediately increased triglyceride and total cholesterol but not HDL levels. These results suggested that chemerin analog regulated insulin secretion related to glucose metabolism and the release of triglycerides in sheep in vivo. This study provides new information about endocrine and metabolic changes in response to chemerin in sheep.