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1.
乳链菌肽前体基因(nisZ)在乳酸乳球菌中的克隆和表达   总被引:7,自引:1,他引:7  
用PCR技术从克隆有完整乳链菌肽生物合成基因簇(来自于乳链菌肽高产菌株L.lactis AL2)的重组噬菌体λHJ-3中扩增了编码乳链菌肽的前体基因,与pMG36e连接得到重组质粒pHJ201,用电击转化法将pHJ201转化到L.lactis NZ9800中,经活性测定和Tricine-SDS-PAGE电泳证实乳链菌肽前体基因获得了功能表达。DNA序列分析表明乳链菌肽高产菌株L.lactis AL2产生的是NisinZ。发现pHJ201d L.lactis NZ9800 中有良好的稳定性。  相似文献   

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聚合酶链反应(PCR)技术已广泛用于DNA基础研究和临床诊断。本文介绍用它来鉴定靶序列,从而进一步筛选阳性重组体。由于引物Tm较高,采用二温段扩增法,确实扩增出10bp靶序列。文章还讨论了扩增较小片段要注意的条件。  相似文献   

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聚合酶链反应(1)是最近几年分子生物学领域中一项重大的技术突破。典型的PCR引物内应含50%G+c,且没有自身互补序列,特别是在其3’-末端不应有内部二级结构。引物与靶DNA的退火温度一般为50℃,但当已有的引物不太符合要求时,就要调整退火温度。本文报道了用PCR方法扩增深红红螺菌draT基因,介绍了当引物Gc含量较低时,可采用适当降低退火温度,然后梯度升温的方法获得PCR产物。  相似文献   

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徐东乎  施红 《生物技术》1997,7(3):39-39
PCR,技术的应用,极大方便了对已知序列基因某一片段的克隆,但在实际操作中某些容易忽视的因素有可能导致实验失败,以下将我们在这方面工作中的几点体会总结如下以供借鉴。1.引物设计。在引物5'端设计酶切位点序列时一般要加保护碱基,如BamHI识别序列为5'-GGATCC,应设计成5'-CGGGATCC,这样才能保证下一步酶切反应的正常进行,因为5'端裸露的位点往往不能为限制酶识别,具体何种位点加什么保护碱基可参阅NewEnglandBiolabs96/97Catalog或其它有关材料。2.片段处理。PCR扩增片段最好用酚:氯仿抽提以除尽Taq酶,单纯…  相似文献   

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本文利用PCR技术建立一种对HSV直接基因分型的方法。在HSV-Ⅰ、Ⅱ两型的DNA多聚酶基因上设计了一条两型共同的上游引物(HDP-B)和两条型特异的下游引物(HDP-1、HDP-2)。三条引物共同组成一个扩增反应体系,在HSV-Ⅰ产生543bp条带,HSV-Ⅱ产生372bp条带,据此在基因水平上对HSV进行分型。5株不同来源的HSV(2株Ⅰ型,3株Ⅱ型)分型结果与病毒分离及血清学方法完全一致。该  相似文献   

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一步法克隆传染性法氏囊病病毒前体多聚蛋白基因   总被引:1,自引:0,他引:1  
刘存仁  梁志清 《病毒学报》2001,17(2):180-182
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  总被引:2,自引:0,他引:2  
Bacillus anthracis lethal toxin (PALF) stimulated the proliferation of human peripheral blood T-cells in vitro. Activation of T-lymphocytes by PALF required the presence of monocytes and did not result from a collaborative effect between T-cells and B-cells. PALF acted directly on monocytes and independently of T-cells. The monocytes contributed to the proliferation of T-cells by secretion of mediator(s). The mitogenic activity of the lethal toxin was dependent on its metalloprotease activity.  相似文献   

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Abstract

Hyaluronic acid (HA) is a natural biopolymer and has long been attracting the attention of biotechnology industry due to its various biological functions. HA production with natural producer Streptococcus equi subsp. zooepidemicus has not been preferred because it has many drawbacks due to its pathogenicity. Therefore, in the present study, Streptococcal hyaluronan synthase gene (hasA) was introduced and expressed in Lactococcus lactis, through the auto inducible NICE system and the effect of nisin amount on the production of HA was examined. Newly constructed plasmid was transformed into L. lactis CES15, produced 6.09 g/l HA in static flask culture after three hours of induction period with initial 7.5 ng/ml nisin concentration within total six hours of incubation. The highest HA titer value ever was reported for recombinant HA-producing L. lactis by examining the effect of initial nisin concentration. We have shown that initial nisin concentration, which used to initiate the auto-inducing mechanism of NICE system and consequently hyaluronan synthase expression, has a direct and significant effect on the produced HA amount. Recently constructed recombinant L. lactis CES15 strain provide significant advantages for industrial HA production than those in literature in terms of production time, energy demand, carbon usage, and safety status.  相似文献   

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多肽抗生素apidaecin基因在乳酸乳球菌中的融合表达   总被引:6,自引:0,他引:6       下载免费PDF全文
利用乳链菌肽(nisin)诱导表达系统,以泛素(ubiquitin)融合蛋白的形式在乳酸乳球菌(Lactococcus lactis)中表达了多肽抗生素apidaecin。利用TricineSDSPAGE和Western blotting均可在诱导后的宿主菌中检测到特异蛋白带。表达产物的最高产量可达宿主菌可溶性蛋白的7.2%左右。在体外用泛素特异性蛋白酶UBPI从融合蛋白中切除泛素后,产物具有明显的抗菌活性。  相似文献   

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【目的】通过基因工程手段增加糖酵解途径中编码限速酶6-磷酸果糖激酶基因Pfk在乳酸链球菌素(nisin)产生菌Lactococcus lactis N8中的表达,增快nisin的产生,从而提高单位时间内nisin的产量,缩短发酵周期。【方法】将pfk基因及编码以c AMP为依赖的蛋白激酶催化亚基基因pka C克隆到表达质粒p MG36e上,将共表达重组质粒转入L.lactis N8中,使Pfk-pka C基因过量表达,得到重组菌株L.lactis N8-p MG36epfk-pka C,并比较该重组菌株与野生菌的生长曲线、胞内6-磷酸果糖激酶活性、发酵上清液的抑菌活性及效价,并从转录水平分析两株菌nis A及pfk-pka C的转录差异,比较野生菌与重组菌在不同葡萄糖含量下培养产nisin的变化。【结果】Pfk基因与pka C基因的过表达对重组菌的生长速度没有明显的影响,却能提高重组菌产nisin的速度,在发酵10 h时nisin的产量比野生菌提高了20%,使得发酵周期缩短近2 h。野生菌及重组菌在不同葡萄糖含量下培养发酵上清液的nisin效价没有明显的变化。【结论】糖酵解途径中6-磷酸果糖激酶基因Pfk的过表达可以加快乳酸乳球菌N8产nisin的速率,缩短发酵周期。  相似文献   

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Besides lactic acid, many lactic acid bacteria also produce proteinaceous metabolites (bacteriocins) such as nisin. As catabolite repression and end-product inhibition limit production of both products, we have investigated the use of alternative methods of supplying substrate and neutralizing or extracting lactic acid to increase yields. Fed-batch fermentation trials using a stillage-based medium with pH control by NH4OH resulted in improved lactic acid (83.4 g/l, 3.18 g/l/h, 95% yield) and nisin (1,260 IU/ml, 84,000 IU/l/h, 14,900 IU/g) production. Removing particulate matter from the stillage-based medium increased nisin production (1,590 IU/ml, 33,700 IU/g), but decreased lactic acid production (58.5 g/l, 1.40 g/l/h, 96% yield). Removing lactic acid by ion exchange resins stimulated higher lactic acid concentrations (60 to 65 g/l) and productivities (2.0 to 2.6 g/l/h) in the filtered stillage medium at the expense of nisin production (1,500 IU/ml, 25,800 IU/g).  相似文献   

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AIMS: Screening for lactic acid bacteria (LAB) producing bacteriocins and other antimicrobial compounds is of a great significance for the dairy industry to improve food safety. METHODS AND RESULTS: Six-hundred strains of LAB isolated from 'rigouta', a Tunisian fermented cheese, were tested for antilisterial activity. Eight bacteriocinogenic strains were selected and analysed. Seven of these strains were identified as Lactococcus lactis and produced nisin Z as demonstrated by mass spectrometry analysis of the purified antibacterial compound. Polymerase chain reaction experiments using nisin gene-specific primers confirmed the presence of nisin operon. Plasmid profiles analysis suggests the presence of, at least, three different strains in this group. MMT05, the eighth strain of this antilisterial collection was identified, at molecular level, as Enterococcus faecalis. The purified bacteriocin produced by this strain showed a molecular mass of 10 201.33 +/- 0.85 Da. This new member of class III bacteriocins was termed enterocin MMT05. CONCLUSIONS: Seven lactococcal strains producing nisin Z were selected and could be useful as bio-preservative starter cultures. Additional experiments are needed to evaluate the promising strain MMT05 as bio-preservative as Enterococci could exert detrimental or beneficial role in foods. SIGNIFICANCE AND IMPACT OF THE STUDY: Only a few antibacterial strains isolated from traditional African dairy products were described. The new eight strains described herein contribute to the knowledge of this poorly studied environment and constitute promising strains for fermented food safety.  相似文献   

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Aims: To characterize the genetic and biochemical features of nisin Q. Methods and Results: The nisin Q gene cluster was sequenced, and 11 putative orfs having 82% homology with the nisin A biosynthesis gene cluster were identified. Nisin Q production was confirmed from the nisQ‐introduced nisin Z producer. In the reporter assay, nisin Q exhibited an induction level that was threefold lower than that of nisin A. Nisin Q demonstrated an antimicrobial spectrum similar to those of the other nisins. Under oxidizing conditions, nisin Q retained a higher level of activity than nisin A. This higher oxidative tolerance could be attributed to the presence of only one methionine residue in nisin Q, in contrast to other nisins that contain two. Conclusions: The 11 orfs of the nisin producers were identical with regard to their functions. The antimicrobial spectra of the three natural nisins were similar. Nisin Q demonstrated higher oxidative tolerance than nisin A. Significance and Impact of the Study:  Genetic and biochemical features of nisin Q are similar to those of other variants. Moreover, owing to its higher oxidative tolerance, nisin Q is a potential alternative for nisin A.  相似文献   

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Nisin is a 34‐amino‐acid antimicrobial peptide produced by Lactococcus lactis belonging to the class of lantibiotics. Nisin displays a high bactericidal activity against various Gram‐positive bacteria, including some human‐pathogenic strains. However, there are some nisin‐non‐producing strains that are naturally resistant owing to the presence of the nsr gene within their genome. The encoded protein, NSR, cleaves off the last six amino acids of nisin, thereby reducing its bactericidal efficacy. An expression and purification protocol has been established for the NSR protein from Streptococcus agalactiae COH1. The protein was successfully crystallized using the vapour‐diffusion method in hanging and sitting drops, resulting in crystals that diffracted X‐rays to 2.8 and 2.2 Å, respectively.  相似文献   

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