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pxyboy

金虫 (小有名气)

[求助] 请虫友帮我看下论文二审的意见已有2人参与

前段时间投了一篇2分多的sci杂志,文章其中一块内容是用pUC19载体构建重组质粒,插入失活乳酸菌的一段基因。结果其中一个评审人对结果提了疑问,主要是对插入失活的基因片段是否真正整合到基因组上了有疑问,让我提交确实的证据,然后我第一次回复他的时候,把野生型菌和工程菌提基因组后分别扩增目的基因,通过二者片段大小不一致(工程菌长度多了段插入的抗性基因)来支持我的论文。结果又返回来二修的意见,还是这个评审人有疑问,仍然是对这个问题有疑问,具体如下,请战友帮我一下,如何回复这个评审人,先谢过了!
The authors haveaddressed my concern about the missing proof for a true knock-out with a newPCR based experiment, showing basically two bands from wildtype and mutant,differing by the size of the Erythromycin gene insert. However, for a fulldesciption of the mutant construction some point are still missing:
First,can the authors verify that the plasmid is not replicating in the host strain?The cited literature does not provide this information, so a citation whichstates that ColE1 type replicons cannot replicate in Lactobacillus would benecessary. If this is not clear from the literature, additional experimentwould be needed to verify this.
Second, and related to the first point, usuallythe first step of a knock-out generation is the formation of a merodiploidafter a first homologous recombination, integrating the whole plasmid into thegenome. Usually a counterselection via a suicide gene on the plasmid is used,to select the true mutants from the merodiploids. This was obviously not donein this case, so the question remains, if the resulting strain is a knock-outor a merodiploid. A very easy test would be to screen the mutants for the presenceof the Amp gene, which is on the plasmid and would be gone in a true mutant.
Third, for characterization of a mutant, acomplementation experiment is necessary, to exclude downstream effects of theintroduced knock-out gene (EryR) on other genes. In this case a merodiploidwould be usful as here one intact copy of the gene is present followed by theintegrated plasmid, so downstream effects should be visible in a merodiploidwhile an effect of the gene knock-out should not be visible. Alternatively theauthors can perhaps use their pMG76e-mur plasmid to create a complementedmutant. In any case this complemented mutant should be included in thephenotypic testing and should behave more or less like the wildtype to provethat the observed effect is really due to the knock-out of the mur gene aloneand nothing else plays a role for the observed phenotype.
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三蛰

铜虫 (小有名气)

【答案】应助回帖

感谢参与,应助指数 +1
将扩增到的片段送测序,这样就确切无疑了。
我不会!
2楼2014-05-28 11:18:51
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朱多龙

木虫 (小有名气)

【答案】应助回帖

★ ★ ★ ★ ★ ★ ★ ★ ★ ★
感谢参与,应助指数 +1
pxyboy: 金币+10, ★★★★★最佳答案, 对我帮助很大,谢谢 2014-05-29 14:49:51
1 确定使用pUC19构建的载体可以在乳酸菌中用于打靶?不能再乳酸菌中复制吗?貌似我还没见过以pUC19做为基础质粒用于构建乳酸菌基因敲除载体的。可以pcr扩增后测序。
2 需要把单交换到双交换这一步筛选的过程详细描述出来。
3 回补实验必须要做。红霉素的正筛标签没删去,是否会影响菌株的一些其它基因正常表达呢?是否由于红霉素的原因造成的?所以必须回补敲除基因。如果可以,最好把ery基因拿下。
3楼2014-05-28 13:07:02
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pxyboy

金虫 (小有名气)

感谢三楼的回复!
4楼2014-05-29 14:49:08
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