Physical characterization of Bacteroides fragilis R plasmid pBF4.
Physical characterization of Bacteroides fragilis R plasmid pBF4.
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脆弱拟杆菌 R 质粒 pBF4 的物理表征。
DOI：
10.1128/jb.145.2.867-872.1981
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发表时间：
1981
影响因子：
3.2
通讯作者：
Macrina,FL
中科院分区：
文献类型：
--
作者：
Welch,RA;Macrina,FL
脆弱拟杆菌V479-1先前已被证明携带一个可自我传递的27 × 10（6）-道尔顿质粒（pBF 4），该质粒赋予林可酰胺-大环内酯类药物抗性。目前的研究主要集中在pBF 4的物理性质。发现质粒以1至2个拷贝/染色体当量存在。pBF 4是遗传稳定的，虽然自发发生的无质粒分离子可以检测到低频率（约1%）。该频率不受溴化乙锭中细胞生长的影响。发现菌株V479-1的所有自发产生的大环内酯-林可酰胺敏感性克隆中约有三分之一含有携带缺失的pBF 4分子。从林可酰胺-大环内酯敏感菌株中独立获得的10个pBF 4的缺失衍生物通过限制性内切酶切割分析与亲本pBF 4进行比较。构建了pBF 4的限制性酶切位点图，并对缺失的位置进行了近似。自退火的pBF 4分子，通过电子显微镜检查，揭示了质粒上存在两对反向重复（IR）序列。IR-1长约400个碱基对，其两个组成成员被约15个内切酶的插入序列隔开。IR-2全长约75个碱基对，其组成成员由4.2个酶分开。所研究的pBF 4的每个缺失都具有在相同IR-2序列处或附近的末端。
Bacteroides fragilis V479-1 has previously been shown to harbor a self-transmissible 27 X 10(6)-dalton plasmid (pBF4) which confers lincosamide-macrolide resistance. The present study has focused on the physical properties of pBF4. The plasmid was found to be present in 1 to 2 copies per chromosomal equivalent. pBF4 was genetically stable, although spontaneously occurring plasmidless segregants could be detected at low frequency (approximately 1%). This frequency was unaffected by growth of cells in ethidium bromide. About one-third of all spontaneously occurring macrolide-lincosamide-sensitive clones of strain V479-1 were found to contain pBF4 molecules that carried deletions. Ten independently obtained deletion derivatives of pBF4 from lincosamide-macrolide-sensitive strains were compared with the parental pBF4 by restriction endonuclease cleavage analysis. A restriction site map of pBF4 was constructed, and the location of the deletions was approximated. Self-annealed pBF4 molecules, examined by electron microscopy, revealed the presence of two pairs of inverted repeat (IR) sequences on the plasmid. IR-1 was about 400 base pairs in length, and its two component members were separated by an intervening sequence of about 15 kilobases. IR-2 was about 75 base pairs in length, and its component members were separated by 4.2 kilobases. Each of the deletions of pBF4 studied had a terminus at or near the same IR-2 sequence.