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31.
为了解海水浴场中大肠杆菌耐药性状况及其耐药基因分布,以大连星海浴场近岸海水样品为研究对象,分离鉴定得到41株大肠杆菌,采用K-B药敏纸片法检测其对9种常用抗生素的耐药性,并对耐药菌株中的耐药基因进行检测。结果表明:41株受试大肠杆菌菌株对四环素的耐药率最高(46%),而对氨曲南的耐药率最低(5%),大肠杆菌的多重耐药率达到34%。采用PCR方法对41株分离菌株进行四环素耐药基因检测,结果显示,仅四环素耐药基因tetA和tetB被检出,其他4种类型四环素耐药基因未被检出。大肠杆菌基因组与质粒DNA中tetA的检出率分别为34%和29%;tetB的检出率分别为2%和12%。相关性分析结果表明大肠杆菌的四环素耐药表型与四环素耐药基因的阳性检出率显著相关。 相似文献
32.
泥螺抗菌肽的初步研究 总被引：2，自引：0，他引：2
将一定浓度的大肠杆菌注射于泥螺体内18h后，将其粘液和血淋巴，于95℃加热10min，10000r／min，4℃离心20min，所得上清液用截留分子量为3kD的超滤装置于10000r／min，4℃下离心1h．滤液用Sephadex G-50分离，得到两个吸收峰．以大肠杆菌和金黄色葡萄球菌作为试验菌株检测抑菌活性，结果表明泥螺经大肠杆菌诱导后，在其血淋巴和分泌的粘液中可分离得到抗菌肽，此多肽具有分子量较小，热稳定性好，对革兰氏阳性细菌和革兰氏阴性细菌均能够起到抑制作用的特点． 相似文献
33.
以剑尾鱼(Xiphophorus helleri)为材料，经Mbo I限制性内切酶消化基因组DNA后，选取500～2000bp的片段连接到经BamH I酶切的pUC18载体上，转化大肠杆菌DH5α构建部分基因组文库。采用设计合成的(AC)7、(GT)7重复序列为引物，PCR筛选部分基因组文库，对其中9个重组阳性克隆进行测序，结果共获得24个微卫星序列，其中Perfect(完美型)13个，占54．2％；Imperfect(非完美型)3个，占12．5％；Compound(混合型)8个，占33．3％。表明(AC／GT)n在剑尾鱼的基因组DNA中含量非常丰富。同时，根据其中3个克隆微卫星的侧翼序列设计引物，PCR扩增剑尾鱼基因组DNA，结果均扩增到目的片段。而且，这3对引物扩增出来的微卫星片段在非选育的剑尾鱼中显示出多态性．而在近交系19代则表现为单态，为剑尾鱼的实验动物化遗传研究提供了理论依据。 相似文献
34.
通过分析超细纤维水镁石的主要化学成分，测定其与大肠杆茵ATCC25922相互作用不同时间后，茵落数、培养基pH值、葡萄糖（GLU）、β-半乳糖酸苷酶以及Mg^2＋等的变化，来研究其相互作用影响。同时做SEM分析，对水镁石短纤维与细茵的作用过程中细菌形态和界面作用情况进行研究以观察超细水镁石粉体对大肠杆菌生长过程的影响。实验结果表明：试验条件下超细水镁石对大肠杆茵的生长有明显促进作用，其中茵落数和β-半乳糖酸苷酶最大是细茵对照管的2倍和5倍左右，同时粉体中Mg^2＋的溶出量相对与粉尘对照管增加2倍～3倍，适量浓度的超细水镁石粉体对大肠杆茵的生长代谢有明显的促进作用。 相似文献
35.
琼胶酶是作用于琼胶的水解酶，在食品、化妆品和制药工业中有广泛的应用。本文建立了一种基于诱导模式和甘油补料优化的高细胞密度和高产β-琼胶酶策略，同时可以较好的控制乙酸盐产量。首先，在诱导前期采用不同的比生长速率（μ）的甘油指数补料策略。结果表明，低的比生长速率（μ=0.2）是细胞生长和β-琼胶酶产生的最佳条件。其次，研究了诱导阶段诱导温度和诱导物浓度对细胞生长和β-琼胶酶产生的影响。当异丙基-β-d-硫代半乳糖苷（IPTG）诱导时，在20℃下0.8mmol/L的IPTG诱导策略对β-琼胶酶的产生效果最佳。采用1.0g/（L·h）的乳糖连续补料策略诱导培养，β-琼胶酶活性达到112.5U/mL，是目前报道的产量最高的β-琼胶酶。此外，β-琼胶酶能直接酶解龙须菜粉，产生新琼寡糖，水解产物为新琼胶四糖（NA4）和新琼胶六糖（NA6）。本文的研究为β-琼胶酶的工业化生产和应用提供了较好的理论依据。 相似文献
36.
Junjie Yi Di Xu Xiaonan Zang Dingyang Yuan Bingran Zhao Li Tang Yanning Tan Xuecheng Zhang 《中国海洋大学学报(英文版)》2014,13(3):497-502
Arthrospira platensis is an economically important cyanobacterium; and it has been used widely in food and pharmaceutical industries. The phycocyanin(PC) from A. platensis is extremely valuable in medicine and molecular biology due to its antioxidation and anti-tumoring activity and applicability as fluorescence protein tag. In present study, two recombinant plasmids, one contained the phycocyanobilin(PCB)-producing genes(hox1 and pcyA) while the other contained the phycobiliprotein gene(cpcB) and the lyase gene(either cpcS/U or cpcT), were constructed and synchronically transferred into E. coli in order to test the the activities of relevant lyases for catalysing PCB addition to CpcB during synthesizing fluorescent PC holo-β-subunit(β-PC) of A. platensis. As was evidenced by the fluorescence emitted at a peak specific for PC, CpcB was successfully synthesized in E. coli, to which co-expressed PCBs attached though at a relatively low efficiency. The results showed that the attachment of PCBs to CpcB were carried out mainly by co-expressed CpcS/U but CpcB also showed some autocatalytic activity. Currently, no CpcT activity was detected in this E. coli expression system. Further studies will be conducted to improve the efficiency of fluorescent PC synthesis in E. coli. 相似文献
37.
Process-based modeling of morphodynamics of a tidal inlet system 总被引：1，自引：0，他引：1
The morphodynamic evolution of an idealized inlet system is investigated using a 2-D depthaveraged process-based model,incorporating the hydrodynamic equations,Englund-Hansen’s sediment transport formula and the mass conservation equation.The model has a fixed geometry,impermeable boundaries and uniform sediment grain size,and driven by shore-parallel tidal elevations.The results show that the model reproduces major elements of the inlet system,i.e.,flood and ebb tidal deltas,inlet channel.Equilibrium is reached after several years when the residual transport gradually decreases and eventually diminishes.At equilibrium,the flow field characteristics and morphological patterns agree with the schematized models proposed by O’Brien (1969) and Hayes (1980).The modeled minimum cross-sectional entrance area of the tidal inlet system is comparable with that calculated with the statistical P-A relationship for tidal inlets along the East China Sea coast.The morphological evolution of the inlet system is controlled by a negative feedback between hydrodynamics,sediment transport and bathymetric changes.The evolution rates decrease exponentially with time,i.e.,the system develops rapidly at an early stage while it slows down at later stages.Temporal changes in hydrodynamics occur in the system;for example,the flood velocity decreases while its duration increases,which weakens the flood domination patterns.The formation of the multi-channel system in the tidal basin can be divided into two stages;at the first stage the flood delta is formed and the water depth is reduced,and at the second stage the flood is dissected by a number of tidal channels in which the water depth increases in response to tidal scour. 相似文献
38.
大肠杆菌感染后栉孔扇贝血淋巴中7种酶活力的变化 总被引：19，自引：0，他引：19
于１９９８年１１月对栉孔扇贝注射大肠杆菌,分别于１,１５,３０ｈ测定了栉孔扇贝血清和血名参与免疫防御的水解,氧化和氧化酶的活力。表明,大肠杆菌激发后,血清实验组的ＡＣＰ活力在１ｈ 于对照组,１５ｈ和３０ｈ时极显著地高于对照组 相似文献
39.
Spatial and Temporal Variations of Tropical Cyclones at Different Intensity Scales over the Western North Pacific from 1945 to 2005 
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下载免费PDF全文 The tropical cyclone （TC） track data provided by the Joint Typhoon Warning Center （JTWC） of the U.S. Navy over the western North Pacific （including the South China Sea） from 1945 to 2005 are employed to analyze the temporal and spatial variations of TCs of different intensity scales. Most of the TCs occurred between 15° and 25°N, from the northern part of the South China Sea to the eastern part of the Bashi Channel until near 140°E. Most of the severe and super typhoons occurred over waters from the eastern part of the Bashi Channel to about 140°E. The TCs in a weakening or steady state take up a weak majority in the area west of 123°E and north of 20°N; those in an intensifying or steady state are mostly found in the area east of 123°E and south of 20°N. For severe tropical storms, typhoons, severe typhoons, and super typhoons, their average decaying rates are all greater than the respective average growing rates; for tropical storms, however, the average decaying rate is smaller than the average growing rate. Generally speaking, the stronger the TC, the faster the intensification （weakening） is. The percentage of weak TCs is higher in June to August while that of strong TCs is higher in September to November. There are annual, interannual, and interdecadal variations in the observed number （every 6 h） and frequency of TCs at different intensity scales. As far as the long-term trend is concerned, the frequency and observed number of tropical storms have a significant linear increase, but the averaged intensity and number of TCs of other intensity categories do not exhibit such a significant linear trend. In E1 Nifio years, the number and percentage of super typhoons are significantly higher, while the total number of tropical storms, severe tropical storms, typhoons, and severe typhoons is significantly lower, and the mean intensity of TCs is prominently stronger; in La Nifia years, however, the opposite comes true. 相似文献
40.
本文采用阿拉伯糖抗性正向突变试验（ara试验）并辅以鼠伤寒沙门氏菌组氨酸营养缺陷回复突变试验（Ames试验）对太湖梅梁湾冬季表层水样品致突变性进行分析研究，ara试验结果表明9个点样品中有5个（主要为入湖河口及近岸样品）表现显著的直接致突变性，加入哺乳动物来源的代谢活化系统S9后，结果仍呈现同样的趋势，A-mes试验在增加两倍半上样剂量的条件下表现出与ara试验大体一致的检出率，在本研究中，ara试验对于成分复杂的环境样品表现更高的检出灵敏度，表明ara试验作为首选方法来检测环境中复杂化学物基因毒性方面有良好前景。 相似文献