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首页> 美国卫生研究院文献>Journal of Bacteriology >Molecular nature of two beta-lactamase-specifying plasmids isolated from Haemophilus influenzae type b.
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Molecular nature of two beta-lactamase-specifying plasmids isolated from Haemophilus influenzae type b.

机译：从b型流感嗜血杆菌分离的两个β-内酰胺酶特异性质粒的分子性质。

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摘要

The molecular nature of two beta-lactamase-specifying plasmids isolated from two separate ampicillin-resistant Haemophilus influenzae type b strains was examined. A 30 X 10(6)-dalton (30-Mdal) plasmid (RSF007) had a copy number of approximately 3 per chromosomal equivalent and a mole fraction guanine plus cytosine content of 0.39. By heteroduplex analysis the 30-Mdal plasmid was found to contain the entire ampicillin translocation DNA segment (TnA) found on R factors of enteric origin. A 3.0-Mdal plasmid (RSF0885) was found as a multicopy pool of approximately 28 copies per chromosomal equivalent, had a mole fraction guanine plus cytosine content of 0.40, and contained only about one-third of the transposable TnA sequence. RSF007 and RSF0885 appeared to be unrelated plasmids in that they share base sequence homology only within the confines of the TnA segment. The 3.0-Mdal Haemophilus plasmid was used to transform E. coli to ampicillin resistance but was found to be unstable in this host in the absence of antibiotic. The possibility that R-plasmids arose in Haemophilus by the translocation of TnA from a donor R-factor onto an indigenous H. influenzae plasmid is discussed.
机译：检查了从两个单独的耐氨苄青霉素的b型流感嗜血杆菌菌株中分离的两个β-内酰胺酶特异性质粒的分子性质。 30 X 10（6）-dalton（30-Mdal）质粒（RSF007）的拷贝数约为每个染色体当量3，鸟嘌呤的摩尔分数加胞嘧啶含量为0.39。通过异源双链分析，发现30-Mdal质粒包含在肠源性R因子上发现的整个氨苄青霉素易位DNA片段（TnA）。发现3.0-Mdal质粒（RSF0885）是每染色体当量约28个拷贝的多拷贝库，鸟嘌呤的摩尔分数加胞嘧啶含量为0.40，并且仅包含可转座的TnA序列的约三分之一。 RSF007和RSF0885似乎是无关的质粒，因为它们仅在TnA区段范围内共享碱基序列同源性。 3.0-Mdal嗜血杆菌质粒用于将大肠杆菌转化为氨苄西林抗药性，但发现该宿主在没有抗生素的情况下不稳定。讨论了通过将TnA从供体R因子转位至本地流感嗜血杆菌质粒而在嗜血杆菌中产生R质粒的可能性。

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