绵羊瘤胃微生物胞外蛋白酶性质的研究

本试验测定了pH、温度和EDTA对纯化的绵羊的瘤胃微生物胞外蛋白酶活性的影响,并用一已知氨基酸排列顺序的肽段(由15个氨基酸组成)作为底物,进一步测定了蛋白酶的酶切位点。结果表明,(1)纯化蛋白酶的最适pH在6.0～6.5之间,最适温度为40℃左右。(2)不同浓度的EDTA(浓度分别为1,10,25,50,75和100mM)对蛋白酶活性没有影响,因而该酶属于丝氨酸蛋白酶类。(3)纯化蛋白酶是一种内肽酶,其酶切位点在组氨酸—酪氨酸(?)、天冬氨酸—丙氨酸(?)、亮氨酸—赖氨酸(?)和(或)缬氨酸—赖氨酸(?)相连的肽键。(4)胰蛋白酶和纯化的蛋白酶虽同属丝氨酸蛋白酶类,但前者对底物具有高度的专一性,后者对底物的专一性不强,这是瘤胃内饲料蛋白质强烈降解的主要原因之     

嗜金微生物研究概况

在广泛文献检索基础上,对嗜金微生物的种属、富集黄金的机理、工业应用价值及潜力进行了概述,为进一步对其开发利用提供科学资料。     

瘤胃微生物总DNA快速提取法研究

本文介绍了一种简便快速地提取瘤胃微生物细胞总DNA的方法,该法是对提取植物的CTAB法进行改进而成。与经典反复冻融 SDS/蛋白酶K裂解法相比,该法可在数小时内高效地提取瘤胃内容物总DNA,经琼脂糖凝胶电泳对所提取瘤胃微生物总DNA进行检测,证明所获得的瘤胃总DNA符合分子生物学操作要求。     

大青叶樱桃根际微生物种群结构及其变化动态

利用选择性培养基,对2年生大青叶樱桃(Cerasus pseudocerasus)根际微生物进行了分离、鉴定和分类,分析了不同物候期根际微生物种群结构的变化。结果表明,从大青叶樱桃根际分离纯化获得的细菌分别属于15个属,以芽孢杆菌属(Bacillus)、假单胞菌属(Pseudomonas)为主;放线菌属于链霉菌属的6个类群,以白色类群(Albosporus)、黄色类群(Flavus)为主;真菌以镰刀菌(Fusarium)和木霉属(Trichoderma)为主。不同生育期根际微生物种群结构不同,落叶期根际细菌种群结构最丰富,萌芽期最少。     

污染土壤的微生物修复原理与技术进展

微生物修复是土壤环境生物修复技术的重要组成部分,是最具发展和应用前景的生物学环保新技术.本文以土壤中重金属及典型有机污染物为对象,从土壤微生物与污染物质的相互作用入手,较为系统地综合评述国内外污染土壤的微生物修复原理与技术,并结合当前土壤污染的新特点,提出了需进一步认识和解决微生物修复过程中出现的新现象和新问题,以不断丰富和拓展土壤环境微生物修复范畴与内涵.     

Application of 16S rDNA Sequence Analysis Technique in Microbial Detection

16srDNA既具有保守性区域。又具有高变性区域,是生物的种属鉴定和系统进化关系的重要分子基础。以16srDNA为目的物的现代分子生物学技术能精确地揭示微生物种类和遗传的多样性,从而16srDNA序列分析成了微生物分类鉴定主要依据。该方法克服了传统微生物培养方法的限制,操作方便、检测快速准确且灵敏度高,已被广泛应用到菌种鉴定、群落对比分析、群落中系统发育及种群多样性的评估等领域,是一种客观和可信度较高的分类方法。     

Effects of antibiotics on soil microorganisms: time and nutrients influence pollution-induced community tolerance

A method for the detection of the effects of antibiotics on soil microbial communities was optimised in the present study. We investigated the influence of measurement time and nutrient status on the pollution-induced community tolerance (PICT), using the sulfonamide sulfachloropyridazine (SCP) as model compound. The tolerance development in soil microcosms that were exposed to SCP under different conditions was compared with the background tolerance in SCP-unexposed microcosms. The tolerance of bacterial extracts from the soil microcosms was determined in Biolog^® multiwell plates as the SCP sensitivity of a range of physiological processes. The background tolerance was not affected by soil nutrient amendments, but an influence of the inoculum density in the microtiter plates was observed. Still, the variance of the background tolerance was low, which is in favour of the usage of community tolerance measurements for a selective detection of a toxicant impact. In line with the assumptions of the PICT concept, soil amendment with SCP led to an increase in community tolerance. This tolerance development was enhanced upon additional soil amendment with fresh pig slurry, and less by alfalfa meal addition. Tolerance increases were observed after a soil exposure to SCP of only 7 days, possibly because nutrient input facilitates the fast adaptation of the soil microbial community. However, a further increase in exposure time led to variable changes in the observed tolerance. Prolonged tolerance detection in the microtiter plates (11 days) enabled a clearer differentiation between different soil treatments, as it better resolved the EC₅₀ values of processes with a high tolerance to bacteriostatic antimicrobial compounds. For the detection of antibiotic effects on soil microbial communities, it is therefore recommended to use nutrient amendments (possibly fresh pig slurry), to standardize the soil exposure time, and to extend the period of Biolog plate measurement beyond 7 days.     

微生物菌群之间配比协调关系的研究

对乳酸杆菌、乳酸球菌、枯草芽胞杆菌、酵母菌、大肠杆菌等菌种进行单独培养和不同比例的混合培养,测定了发酵过程中pH值、活菌数量及光密度的变化情况。结果表明,与含有25%混合菌液的发酵麸皮相比,含50%混合菌液的发酵麸皮,在发酵24 h后的需氧或厌氧活菌总数都有升高趋势(P>0.05),发酵1周后其pH值的下降趋势明显(P<0.05),说明乳酸菌数越多使pH下降越大。利用需氧(LB)和厌氧(MRS)培养液分别交叉培养需氧菌和厌氧菌,均能在相应的培养基上生长。充分说明厌氧菌和需氧菌混合培养在理论上是可行的。但是,如果用滤菌膜过滤后的培养过乳酸菌的MRS培养基来培养需氧菌时,这些菌种均不能在滤液中生长。     

Inoculation of root microorganisms for sustainable wheat-rice and wheat-black gram rotations in India

The scarcity of non-renewable resources such as soils and fertilizers and the consequences of climate change can dramatically influence the food security of future generations. Mutualistic root microorganisms such as plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) can improve plant fitness. We tested the growth response of wheat (Triticum aestivum [L.]), rice (Oriza sativa [L.]) and black gram (Vigna mungo [L.], Hepper) to an inoculation of AMF and PGPR alone or in combination over two years at seven locations in a region extending from the Himalayan foothills to the Indo-Gangetic plain. The AMF applied consisted of a consortium of different strains, the PGPR of two fluorescent Pseudomonas strains (Pseudomonas jessenii, R62; Pseudomonas synxantha, R81), derived from wheat rhizosphere from one test region. We found that dual inoculation of wheat with PGPR and AMF increased grain yield by 41% as compared to un-inoculated controls. Yield responses to the inoculants were highest at locations with previously low yields. AMF or PGPR alone augmented wheat grain yield by 29% and 31%, respectively. The bio-inoculants were effective both at Zero and at farmers’ practice fertilization level (70 kg N ha⁻¹, 11 kg P ha⁻¹ in mineral form to wheat crop). Also raw protein (nitrogen × 5.7) and mineral nutrient concentration of wheat grains (phosphorus, potassium, copper, iron, zinc, manganese) were higher after inoculation (+6% to +53%). Phosphorus use efficiency of wheat grains [kg P grain kg⁻¹ P fertilizer] was increased by 95%. AMF and PGPR application also improved soil quality as indicated by increased soil enzyme activities of alkaline and acid phosphatase, urease and dehydrogenase. Effects on rice and black gram yields were far less pronounced over two cropping seasons, suggesting that AMF and PGPR isolated from the target crop were more efficient. We conclude that mutualistic root microorganisms have a high potential for contributing to food security and for improving nutrition status in southern countries, while safeguarding natural resources such as P stocks.     

免耕法对土壤微生物和生物活性的影响

本文比较常耕和免耕法对土壤微生物和生物学活性的影响.结果表明,连续免耕6-7年的砂壤土中微生物的数量较集中分布于上表层,常耕处理则相对均匀地分布于经常翻动的土层中.0-7cm表层土壤中微生物的优势种群在两种耕法中有一定差异,特别是霉菌.免耕处理0-7cm土壤培养1天的呼吸活性是常耕处理的2.1倍,尿酶活性是常耕处理的1.6倍.但随着土层的加深,免耕处理的呼吸活性、尿酶活性下降很快,至7-14cm处分别下降56%、71%.培养40天时0-7cm土壤无机氮释放量免耕和常耕处理分别为48.1、34.5mgN/kg,而7-14cm土层则分别为21.5、29.1mgN/kg.不加碳源只加入硫铵培养3天土壤中无机氮的减少在10%左右,免耕上表层0-7cm土壤减少较多,反映土壤微生物对无机氮的固定作用.长期免耕使具有高生物学活性的土层变得浅薄,而常耕处理则较为深厚.