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Direct selection for curing and deletion of Rhizobium plasmids using transposons carrying the Bacillus subtilis sacB gene 总被引:13,自引:0,他引:13
We have constructed derivatives of the transposon Tn5 carrying the mob site (oriT) of plasmid RP4, and an nptI-sacB-sacR cassette [Ried and Collmer, Gene 57 (1987) 239-246]. The mob site, in conjunction with the antibiotic-resistance markers carried on the transposons, allows identification of transposon inserts in cryptic plasmids by mobilisation to other strains. The sacB-sacR genes allow direct selection for the loss or curing of plasmids, because only strains which no longer contain an active sacB gene are able to grow on media containing sucrose. We have tested these transposons in four strains of Rhizobium leguminosarum and two strains of Rhizobium meliloti, and have been able to demonstrate curing of several large cryptic plasmids, and generation of large deletions in many other plasmids. This method has enabled us to show that the R. leguminosarum plasmids pRL12JI and pR1eVF39f carry auxotrophic markers, and that the plasmid pR1eVF39c carries genes which affect colony morphology. 相似文献
83.
H. Wieler H. W. Hoffmanns A. Kippels S. Huhndorf A. Düx 《Radiation and environmental biophysics》1987,26(3):219-226
Summary The simultaneous use of intraarterial Cis-Platinum and Radiotherapy (CP/RT) was found to be a very effective and relatively little burdened treatment for a palliative treatment concept. This affects life quality as well as the remission - and survival times. The fast and continual remission with low CP/RT concentrations, even in extreme palliative cases, is surprising. CP/RT treatment shows additive and synergistic effects which are not explainable by the single effects of the cis-platinum dose used (60 mg/1.73 m2 in our case) or the total irradiation dose (e.g., 5 Gy TD) or the fractionation (e.g., 5 × 1 Gy), especially since the doses of each which were used are by themselves without therapeutic relevance. Only the combination of the modalities with a low dose two-day preradiation program induced the described effects.Dedicated to Prof. L.E. Feinendegen on the occasion of his 60th birthday 相似文献
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The emission maximum of the single tryptophan residue of melittin was measured in the presence of phosphatidylethanolamine liposomes and Escherichia coli cytoplasmic membranes. In both cases, the fluorescence maximum was shifted to shorter wavelengths indicating a transfer of the indole ring to an apolar environment. E. coli membranes were labelled in position 2 of their phospholipids with [14C]oleic acid. These membranes were used for measuring the activity of an endogenous phospholipase A2. A slow hydrolysis is observed, which can be accelerated by adding melittin. The extent of the stimulation depends on the molar ratio of melittin to membrane phospholipid. Under suitable conditions, the initial rate of hydrolysis is six to seven times higher in the presence than in the absence of melittin. The action of the phospholipase A2 from bee venom is also stimulated by melittin. An identical stimulation was observed with either E. coli membranes or pure phosphatidylethanolamine liposomes as substrate. 相似文献
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DA/DAPI heteromorphisms in acrocentric chromosomes other than 15 总被引:1,自引:0,他引:1
90.