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71.
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Erwinia amylovora causes fire blight of apple, pear, and other members of the Rosaceae family. The enzyme LuxS catalyzes the last step in the
production of autoinducer-2 (AI-2), a molecule implicated with quorum sensing in many bacterial species. It is now well recognized
that LuxS also plays a central role in sulfur metabolism and in the activated methyl cycle, which is responsible for the generation
of S-adenosyl-l-methionine. A research paper has reported that luxS is not involved with quorum sensing in Er. amylovora, but in our study, Er. amylovora strain NCPPB1665 (Ea1665) produced luxS-dependent extracellular AI-2 activity. Additionally, the maximal AI-2 activity occurred during late-exponential and early-stationary
growth phases and diminished during the stationary phase. The luxS mutant of Ea1665 was constructed, and the phenotypes of a defined luxS mutant have been characterized. Inactivation of luxS in Ea1665 impaired motility, extracellular polysaccharide (EPS) production, and tolerance for hydrogen peroxide, and reduced virulence
on pear leaves.
Yan Gao and Junxian Song contributed equally to this research. 相似文献
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Red重组系统及在微生物基因敲除中的应用 总被引:6,自引:0,他引:6
在完成了对各种微生物基因组的测序以后,功能基因学的研究变得尤为重要。研究基因功能最直接的方法便是将待研究的基因失活。最初构建基因突变体是采用大肠杆菌的RecA系统,但是RecA重组系统操作复杂,重组效率低。最近建立了Red重组系统,该系统由3个蛋白组成:α蛋白(即λ核酸外切酶),β蛋白,Gam蛋白。应用Red系统进行基因敲除,可以直接利用线性打靶DNA,两侧同源臂长度在35~60 bp即可发生同源重组,且重组效率高。
Abstract:Since many DNA-sequencing projects of varied microorganisms have been completed,studies on their functional genomics become more important.Inactivation of an interesting gene is a direct method to characterize its function.Though the Esherichia coli RecA recombination system can be used to produce gene mutants,it needs a complex manipulation process.Furthermore,its efficiency is very low.Recently a Red recombination system was developed.This recombination system consists of three proteins:α protein(λ exonuclease),β protein and Gam protein.In this system,the linear targeting DNA which contains a selectable marker flanked with a homologous region as short as only 35~60 bp can be directly targeted for gene knock-out with a higher efficiency. 相似文献
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Age determination is the basis of determining the postmortem interval using necrophagous fly larvae. To explore the potential of using cuticular hydrocarbons for determining the ages of fly larvae, changes of cuticular hydrocarbons in developing larvae of Chrysomya rufifacies (Macquart) (Diptera: Calliphoridae) were investigated using gas chromatography with flame-ionization detection and gas chromatography-mass spectrometry. This study showed that the larvae produced cuticular hydrocarbons typical of insects. Most of the hydrocarbons identified were alkanes with the carbon chain length of 21-31, plus six kinds of alkenes. The hydrocarbon composition of the larvae correlated with age. The statistical results showed that simple peak ratios of n-C29 divided by another eight selected peaks increased significantly with age; their relationships with age could be modelled using exponential or power functions with R(2) close to or > 0.80. These results suggest that cuticular hydrocarbon composition is a useful indicator for determining the age of larval C. rufifacies, especially for post-feeding larvae, which are difficult to differentiate by morphology. 相似文献
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空间异质性对样地数据空间外推的影响 总被引:1,自引:0,他引:1
应用模型结合的方法模拟了3个空间异质性等级预案下反应变量(气候变化下景观水平的树种分布面积)的变化情况,并分析模拟结果在预案之间的差异性,探讨了环境空间异质性对样地观测到的树种对气候变化响应向更大空间尺度外推的影响.结果表明:空间异质性在一般情况下对样地数据向土地类型尺度外推没有影响,而对样地尺度外推到海拔带尺度的影响则有较复杂的情况.对于对气候变化不敏感的树种以及非地带性树种,空间异质性对样地数据向海拔带尺度外推没有影响;对于大多数对气候变化敏感的地带性树种而言,空间异质性对样地数据向海拔带尺度外推则有影响. 相似文献