嗜碱芽孢杆菌木聚糖酶在苇浆漂白中的应用初探

采用嗜碱芽孢杆菌NT-9产生的木聚糖酶对苇浆进行生物漂白预处理,并分析了酶处理苇浆的理化性能。结果表明,在酶剂量5-25IU·g-1样品、50℃、pH8.6条件下处理120min,苇浆失重率随酶剂量的增加而上升,苇浆的白度也有一定提高。X-衍射分析显示,酶处理苇浆纤维的相对结晶度降低了2.43%,扫描电镜也证实酶处理苇浆纤维表面形貌发生了一些明显的变化。     

枯草芽胞杆菌DarA蛋白的鉴定及其原核表达

目前,我国全面禁止饲料中添加抗生素,寻找新型的抗生素替代物是当前研究的热点之一。本研究旨在分离枯草芽胞杆菌SXAU18所产具有抗菌活性的蛋白物质,并通过原核表达系统获得其具有抗菌活性的重组蛋白。试验选用硫酸铵沉淀、氯仿抽提、分子截留等蛋白提取技术,对枯草芽胞杆菌SXAU18产生的抗菌蛋白进行分离纯化;通过SDS-PAGE技术和牛津杯扩散法检测分离到的蛋白物质的抑菌活性;通过质谱、生物信息学技术分析预测目的蛋白的基因序列;利用大肠杆菌表达系统和AKTA蛋白纯化系统对目的蛋白进行表达和纯化;借助牛津杯扩散法鉴定重组蛋白的抑菌活性。结果表明,枯草芽胞杆菌SXAU18所产的抗菌物质为相对分子质量15 ku左右的蛋白质,含有共同的特定氨基酸序列—GSSIFGLAPGK,对金黄色葡萄球菌、表皮葡萄球菌、藤黄微球菌和单增李斯特菌有较好的抑菌活性;通过质谱分析和生物信息学推测SXAU18所产的（主要）抑菌蛋白为DarA;经诱导表达的重组蛋白DarA主要以可溶性上清蛋白形式存在,纯化后的DarA蛋白为单一条带,并具有良好的抑菌活性。结果提示,分离自枯草芽胞杆菌SXAU18的抗菌蛋白DarA具有抑制金黄色葡萄球菌、表皮葡萄球菌、藤黄微球菌和单增李斯特菌生长的活性,且可以通过体外表达获取该蛋白。     

Dietary Bacillus subtilis C-3102 Supplementation Enhances the Exclusion of Salmonella enterica from Chickens

Among the reported probiotic Bacillus strains, B. subtilis C-3102 has the unique potential to improve feed uptake under stress conditions in the broilers, piglets, and cows. In this study, we sought to evaluate the protective effect of feed additive probiotic Bacillus subtilis C-3102 against Salmonella enterica infection of specific pathogen-free (SPF) chicks in floor pens in two experiments. In the experiment-1, the chicks in the control group (n=32) were fed a basal diet and those in the C-3102 group (n=32) were fed a basal diet supplemented with 1×10⁶ CFU/g of feed for 28 days. On day 7 post-challenge with S. enterica, there was no significant change in the body weight between both the groups throughout the test period, whereas detection rates of S. enterica in the C-3102 group were significantly lower in the cecum and liver on days 21 and 14 post-challenge, respectively. In the experiment-2, minimum dosage of C-3102 cells required to protect Salmonella infection was evaluated using 3 dosages. Chicks were divided into four groups, fed with different dosages of C-3102 (1×10⁶, 5×10⁵, 3×10⁵, and 0 CFU/g of feed), and challenged with S. enterica (2.8×10⁸ CFU/chicken). S. enterica infection was completed within 7 days post- challenge and was almost excluded from the liver and spleen on day 21 post- challenge in the control group. Average values showed a trend for higher infection rates in the control group >3×10⁵>5×10⁵>1×10⁶ CFU/g on days 14 and 21 post-challenge. These results suggest that B. subtilis C-3102 supplementation has the potential to reduce S. enterica infection rates and/or to accelerate the exclusion of S. enterica from the chicks.     

Effect of Bacillus subtilis C-3102 supplementation in milk replacer on growth and rumen microbiota in preweaned calves

We aimed to assess the effect of feeding Bacillus subtilis C-3102 on the growth and rumen microbiota in the preweaned calves. Twelve newborn Japanese Black calves were randomly allocated to either the control (n = 6) or the treatment (n = 6) groups in the present study. Calves in the treatment group were offered B. subtilis C-3102 supplemented milk replacer throughout the preweaning period. Rumen fermentation during the first 21 days of life seemed to be slightly suppressed by feeding B. subtilis C-3102. This fermentation shift was probably attributed to the lower abundance of the core members of rumen microbiota until 21 days of age in the calves fed B. subtilis C-3102. However, feeding B. subtilis C-3102 did not influence the abundance of the core members of rumen microbiota at 90 days of age. Distribution of Sharpea spp. and Megasphaera spp., which potentially contribute to low methane production and are regarded as beneficial rumen bacteria, was higher in the rumen of calves fed B. subtilis C-3102 at 90 days of age. These results suggest that B. subtilis C-3102 supplementation in milk replacer could potentially contribute to the improvement of feed efficiency after weaning via the establishment of beneficial rumen bacteria.     

巨大芽孢杆菌在油菜根部定殖和促生作用的研究

采用基因标记技术和常规方法跟踪巨大芽孢杆菌A6 (gusA)在缩影系统油菜根际的定殖情况。A6 (gusA)菌在油菜不同根段部位的定殖密度表现从上到下逐渐递减的现象。随着接种后时间的延长而逐渐下降。在根段 8cm以外的根区几乎检测不到接种菌。在油菜播种后 3d ,定殖密度可达最高水平 (8 7×10 5cfug-1根 ) ,然后急速下降 ,30d后保持相对稳定的较低水平 (2 2× 10 2 cfug-1根 )。在促生试验中 ,表现在不同程度上增加植株干重、全氮、全磷和全钾的含量     

Decomposition processes under Bt (Bacillus thuringiensis) maize: Results of a multi-site experiment

The effects of maize expressing the Bacillus thuringiensis Cry1Ab protein (Bt maize) on decomposition processes under three different European climatic conditions were assessed in the field. Farming practices using Bt maize were compared with conventional farming practices using near-isogenic non-Bt maize lines under realistic agricultural practices. The litter-bag method was used to study litter decomposition and nitrogen mineralization dynamics of wheat straw. After 4 months incubation in the field, decomposition and mineralization were mainly influenced by climatic conditions with no negative effect of the Bt toxin on decomposition processes.     

Estimation of synergistic effect of humic fertilizer and Bacillus subtilis on lettuce plants by reflectance measurements

Previous research showed that the use of plant growth promoting rhizobacteria helped to increase nutrient use efficiency. The individual and combined effects of combined action of humic fertilizer and rhizobacteria Bacillus subtilis No. 2 on the lettuce yield, chlorophyll, total nitrogen and nitrate-(N) contents in lettuce leaves was studied. Traditional biochemical analysis and crop reflectance method were compared. Vegetation Indices and key spectrum characteristics - a median of frequency spectrum and bandwidth of frequency spectrum were used to estimate chlorophyll content in plant leaves.

The synergistic effect of bacteria and humic fertilizer was evidenced by increase in N and chlorophyll contents and in decreased nitrates content in lettuce leaves. Humic fertilizer resulted in decreased nitrates concentration in plants, whereas bacillus (B). subtilis No. 2 increased total N and chlorophyll contents. Results indicated that the application rate of humic fertilizer may be reduced when B. subtilis No. 2 is also applied.     

Effect of increasing oxygen concentration on total denitrification and nitrous oxide release from soil by different bacteria

Summary The effect of increasing oxygen concentrations (0, 5, 10 and 20 Vol% O₂) on total denitrification and N₂0 release was studied in model experiments using a neutral pH loamy soil relatively rich in easily decomposable organic matter and supplied with nitrate (300 g nitrate N/g dry soil). The sterilized soil was inoculated with three different denitrifying bacteria (Bacillus licheniformis,Aeromonas denitrificans andAzospirillum lipoferum) and incubated (80% WHC, 30°C). The gas volume was analysed for O₂, CO₂, N₂O, NO and N₂ by gas chromatography and the soil investigated for changes in ammonium, nitrite, nitrate, pH, total N and C as well as water-extractable C. WithB. licheniformis andAeromonas denitrificans total denitrification increased remarkably with increasing pO₂ as the result of intensified mineralization.Azospirillum lipoferum, however, showed the highest activity at 5 vol% O₂. WithB. licheniformis N₂O was released only in anaerobic conditions and at 5 Vol% O₂ (maximum) or 10 Vol% 02, but not at 20 Vol%, whereasAeromonas denitrificans produced N₂O only in the presence of He gas (maximum) or at 5 Vol% O₂. In contrast to these bacteria, N₂O production withAzospirillum lipoferum was restricted to 10 Vol% O₂ (maximum) and to 20 Vol% 02, with some traces at 5 vol% O₂. With a certain set of conditions, total denitrification and N₂O formation seem to be governed by the mineralization rate of the organisms in question. The increased demand for electron acceptors by a high turnover rate rather than the presence of anaerobic conditions seems to have determined the rate of denitrification.     

H5N1型禽流感病毒血凝素HA1蛋白在苏云金芽胞杆菌细胞表面的展示及其免疫原性

利用苏云金芽胞杆菌S-层蛋白CTC表面展示系统研究在细胞表面展示H5N1型禽流感病毒HA1蛋白的可行性及其免疫原性，为研制既安全有效又能常温长期保藏和运输的禽流感口服基因工程疫苗奠定基础。用部分ha1基因（ha1p）代替S-层蛋白ctc基因中部且位于表面锚定序列slh下游的片段，构建了融合基因ctc-ha1p和 csa-ctc-ha1p；利用电脉冲转化法将含融合基因的重组质粒转入苏云金芽胞杆菌无质粒突变株BMB171中，获得了重组菌株BCCH（含ctc-ha1p，并导入一个载有协助细胞表面展示的csaAB操纵子的质粒）和CH（含csa-ctc-ha1p）。通过血凝和血凝抑制试验以及小鼠免疫学实验证实，2个重组菌株均成功地在细胞表面展示了重组HA1蛋白并具有一定的特异性和免疫原性，其中，CH的效果强于BCCH，说明csa-ctc-ha1p这种融合基因的构建方式更胜一筹。研究结果表明，苏云金芽胞杆菌S-层蛋白CTC表面展示系统可用来研制禽流感口服疫苗。     

内生枯草芽孢杆菌B-001菌株内生定殖研究及生物学特性

用浸种、浸根、淋根、伤茎、伤叶和喷雾等接种方法测试枯草芽孢杆菌B-001菌株入侵烟草植株的途径,发现该菌可通过自然孔口和伤口入侵寄主植物;取接种植株的茎部组织切片在电镜下观察,发现该菌株在烟草的微管束和细胞内定殖。生长特性研究结果表明该菌株最适生长pH为7.5,最适生长温度为30℃,48～96h内处于稳定生长期。