Background
Using synthetic biology methods, the Escherichia coli K-12 genome was reduced by making a series of planned, precise deletions. The multiple-deletion series (MDS™) strains (1), with genome reduction of up to 15%, were designed by identifying non-essential genes and sequences for elimination, including recombinogenic or mobile DNA and cryptic virulence genes, while preserving robust growth and protein production. Genome reduction also led to unanticipated beneficial properties, including high electroporation efficiency and accurate propagation of recombinant genes and plasmids that are unstable in other strains. Subsequent deletions and introduction of useful alleles produce strains suitable for many molecular biology applications. Recently, Scarab has built on the MDS™42 foundation strain, by creating the MDS™42 Meta LowMut ΔrecA strain. It improves the already low mutation rate of the MDS™42 foundation strain. The MDS™42 Meta LowMut ΔrecA strain has been engineered to greatly reduce error-prone repair, which reduces the mutation rate to almost zero, even under the most stressful conditions, thus ensuring the most accurate replication of your plasmid. In addition, its metabolism has been optimized to enable ULTRA high density fermentation ~300 OD600 in minimal media at the 10 liter scale, which in turn enables ULTRA high biotherapeutic yields, protein or plasmid.
Figures
Figure 1. MDS™42 Meta LowMut ΔrecA has the Lowest Mutation Rate Under Stress. Mutation rates of various strains under unstressed and stressful conditions were determined. Stress conditions include overproduction of GFP, overproduction of a toxic peptide from pSG-ORF238 and treatment with mitomycin-C. All measurements were made using the cycA fluctuation assay, error bars represent 95% confidence intervals for the average of 3 independent measurements. BL21(DE3) failed to grow in the presence of 0.1 μg/ml mitomycin-C. ANOVA revealed a significance of p < 0.0001. Pairwise t-tests were conducted for each strain under a given condition compared to the corresponding MDS™42_lowmut strain. Figure 2: Non-Expressing Plasmid Mutations Accumulate rapidly in BL21(DE3), When a Toxic Methyltransferase is Overproduced. SinI methyltransferase was expressed from pSin32. Plasmids were isolated at various intervals and screened (by transformation in McrBC+ and McrBC- hosts) for mutations resulting in loss of function of the enzyme. Error bars represent 95% confidence intervals for the average of 3 independent measurements of mutant plasmid ratios. ANOVA revealed a significance of p < 0.005. Pairwise t-tests of each MDS™42_lowmut_mcrBC sample were done with the corresponding MDS™42 mcrBC and BL21(DE3) mcrBC sample, respectively. Starting from 10 hours, all MDS™42_lowmut_mcrBC samples differed significantly from the MDS™42 mcrBC (p < 0.01) or BL21(DE3) mcrBC (p < 0.005) samples. Figure 3: Multiple Deletion Strains tolerate "deleterious” genes. A chimeric gene composed of VP60 of rabbit hemorrhagic disease virus fused to the B subunit of cholera toxin (CTX) was very unstable in E. coli. Individually, both genes were stable in E. coli HB101, C600 and DH10B, but pCTXVP60 carrying the fusion gene in the same hosts did not produce fusion protein and was recovered in low yields. All recovered plasmids contained mutations in the CTXVP60 open reading frame, virtually all resulting from IS insertions. In contrast, the recombinant plasmid was completely stable in MDS™; normal yields of plasmid DNA were obtained. Representative restriction patterns of pCTXVP60. (A) Plasmid DNA from MDS™42 was transformed and propagated in the indicated host, then digested with NcoI and EcoRI. A representative of each restriction pattern was purified and sequenced. M, molecular weight marker, 1 kbp ladder; 1, MDS™41, no insertion; 2, MDS™42, no insertion; 3, DH10B, IS10 insertion; 4, DH10B, IS10 insertion/deletion; 5, C600, IS5 insertion; 6, C600, IS1 insertion; 7, C600, IS1 insertion. (B) Relative position of the IS element insertion sites in the CTXVP60 reading frame determined for the five examples presented. Figure 4: Plasmid stability in different host strains. Left: during four subcultures of pT-ITR, a plasmid with viral LTR segments; Lane 0, isolated plasmid DNA before subculture, lanes 1-4, successive subcultures. Plasmid DNA was digested with restriction enzymes and analyzed by agarose gel electrophoresis. KpnI cuts the plasmid at a single site, but in MG1655 two bands indicate a deletion in the plasmid. MscI cuts at two locations, but in MG1655 a third intermediate band confirms that the plasmid is deleted. Right: Stability of four variants of a Lentiviral expression plasmid in MDS™42 ΔrecA and Stbl3™ (Life Technologies), showing the proportion of transformants containing intact plasmids (Table 2 BioTechniques 43:466-470 (October 2007))(2).
Specifications
Kit Components MDS™42 Meta LowMut ΔrecA Electrocompetent Cells pUC19 Control DNA (10 pg/µl) SOC Medium Genotypes MG1655 multiple-deletion strain (1) relA* Δrph ΔarpA ΔiclR ilvG+ ΔdinB ΔpolB ΔumuDC (2) ΔrecA(1819). Quality Control Transformation efficiency is tested using pUC19 Control DNA, in duplicate. Transformed cells are plated onto LB plates containing 50 µg/ml carbenicillin. Transformation efficiency is > 5 x 109 cfu/µg DNA. Storage Conditions Store components at –80°C. Do not store cells in liquid nitrogen.
Related Products
White Glove IS Detection Kit
Support
Product Manuals MDS™42 Meta LowMut ΔrecA Electrocompetent Cell Kit Papers
- Pósfai G, et al., (2006) Emergent properties of reduced-genome Escherichia coli. Science 312:1044-6.
- Csörgő et al. (2012) Low-Mutation-Rate, Reduced-Genome Escherichia coli an Improved Host for Faithful Maintenance of Engineered Genetic Constructs Microbial Cell Factories, 11:11.
- Chacko S. Chakiath, CS & Esposito, D (2007): Improved recombinational stability of lentiviral expression vectors using reduced-genome Escherichia coli. BioTechniques 43:466-470.
Patents & Disclaimers
Products are sold for non-commercial use only, under Scarab Genomics limited use label license: Limited Label Use.Scarab is providing you with this Material subject to the non-transferable right to use the subject amount of the Material for your research at your academic institution. The Recipient agrees not to sell or otherwise transfer this Material, or anything derived or produced from the Material to a third party. NO RIGHTS ARE PROVIDED TO USE THE MATERIAL OR ANYTHING DERIVED OR PRODUCED FROM THE MATERIAL FOR COMMERCIAL PURPOSES. If the Recipient makes any changes to the chromosome of the Material that results in an invention in breach of this limited license, then Scarab will have a worldwide, exclusive, royalty-free license to such invention whether patentable or not. If the Recipient is not willing to accept the terms of this limited license, Scarab is willing to accept return of this product with a full refund, minus shipping and handling costs. For information on obtaining a license to this Material for purposes other than research, please contact Scarab’s Licensing Department. Scarab Genomics’ technology is covered by U.S. Pat. No. 6,989,265 and related foreign applications. Clean Genome® is a registered trademark of Scarab Genomics, LLC.
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大家都是用什么方法挑选细胞单克隆的
单克隆:单克隆是指‘子代来源于一个母体.
细胞培养:细胞的大规模克隆.细胞培养,既包括微生物细胞的培养,细胞培养技术可以由一个细胞经过大量培养成为简单的单细胞或极少分化的多细胞.
单克隆一般常指动植物细胞的克隆,细胞培养一般是指动物、微生物等细胞的细胞克隆.
二者没有什么明显区别.单克隆在单克隆抗体制备中比较常见.其实是对骨髓瘤细胞的细胞培养.
目标蛋白对细胞有毒性,导致细胞死亡;
转染试剂以及DNA用量信息需要优化,否则对细胞具有伤害;
细胞贴壁转染之后没有正常换液。
建议:考虑对目标蛋白进行截短构建、尝试其他细胞系统;摸索转染试剂以及DNA用量信息,如果转染试剂毒性太大,可以考虑尝试义翘转染试剂sinofection;对转染后的细胞进行换液处理,如果细胞状态感觉不够理想,可以考虑添加一些血清来帮助细胞恢复健康。
以上所有分析、建议的前提是,细胞培养、无菌操作等等都没有问题。祝顺利,加油~
我转的是7901、7901/DDP两种细胞,前者7901细胞很容易就转上,并且转后,状态良好,可是7901/DDP一转就死,我用的是吉玛慢病毒,转24小时后换液,刚开始一两天,没有异常,但后来细胞慢慢就死了,并且不是漂浮的,很多是贴着壁死,像是瓦解了一样
这是未转时细胞的样子
这是细胞转后,死亡的样子
并且即使是有些细胞未死,细胞后来也变得很脏,感觉有很破碎的细胞碎片
本人实验小白,**园子里大神指点,急,实在不知道怎么回事
“转化”是指含外源基因的重组质粒(载体)将外源基因直接导入原核细胞(如细菌);
“转导”指通过重组病毒载体将外源基因导入真核细胞或原核细胞;
“转染”指重组质粒载体或游离核苷酸在脂质体等介导下进入真核细胞;
“感染”在基因转移实验中强调重组病毒载体入侵受体细胞的过程。
在使用这4 个名词时, 应仔细分析基因转移实验的四要素——转移物、载体、介导方法、受体细胞类型,而正确区 分载体和受体细胞类型是辨析的关键点。当载体是重组质粒时,如受体细胞是原核细胞应使 用“转化”,如受体细胞是真核细胞则使用“转染”;当载体是重组病毒时,如强调转移物进 入受体细胞应使用“转导”,如强调重组病毒载体进入受体细胞的过程则使用“感染”。
各位版友求助,
我使用Hek293构建转染模型,瞬转5质粒,用lipo2000做转染体系。
转染48h,发现荧光较强的细胞都在爬片的边缘,比例十分少。是因为我添加试剂的手法不对吗。
同时也发现加入转染体系后细胞状态特别差。想问一下用lipo2000时可以用无双抗的10%FBSDMEM吗。我转染前6h现在用的是纯DMEM,不含FBS。
请各位大神帮忙
转染分2种,一种是瞬时转染,即转染后让细胞表达目的蛋白后即提取蛋白,提一次蛋白,转染一次,这种方式一般不传代;
另一种转染为稳定转染,转染后加入一定选择压力进行筛选,没有转染的细胞不能存活,只留下转染的细胞,这种情况下可以筛选单个转染细胞,构建稳定表达某一特定蛋白或基因的细胞系。
其次要看下你选择单位的规模如何,做的比较好的,还是上海这边的,你可以看下基尔顿生物,原代细胞培养,动物造模,整体课题外包。
暂无品牌问答