Extrachromosomal elements in a variety of strains representing the Bacteroides fragilis group of organisms
Extrachromosomal elements in a variety of strains representing the Bacteroides fragilis group of organisms
复制标题
代表脆弱拟杆菌群的多种菌株中的染色体外元件
DOI：
10.1128/iai.14.4.955-964.1976
复制
发表时间：
1976
影响因子：
3.1
通讯作者：
F. Macrina
中科院分区：
文献类型：
--
作者：
W. H. Tinnell;F. Macrina
先前的核酸关联研究已经确定了脆弱拟杆菌生物群的至少九种脱氧核糖核酸（DNA）同源性类别。使用这些类别作为分类框架，我们筛选了B的代表菌株。fragilis组的染色体外（质粒）DNA的存在。对[3 H]胸腺嘧啶标记的细胞裂解物进行十二烷基硫酸钠盐沉淀，并使用氯化铯-溴化乙锭平衡离心法分析来自此类制备物的上清液级分。以这种方式检查每组的一个菌株。判定其中5个菌株不含可检测的质粒DNA;然而，观察到4个菌株产生对应于共价闭合环状质粒DNA的卫星条带。将来自这样的梯度的质粒DNA通过中性和碱性蔗糖梯度进行速度沉降以确定分子大小。在B中发现了一个分子量为23 × 10（6）的质粒。fragilis菌株代表该物种的一个DNA同源群，而在B中发现了3 × 10（6）分子量质粒。fragilis菌株代表第二同源群。类似地，在多形拟杆菌菌株中发现了一个31 × 10（6）-分子量质粒，代表该物种的一个DNA同源群，而在B中发现了一个3 × 10（6）-分子量质粒。代表第二同源群的多形核菌株。在所有情况下，小分子量质粒以每个染色体当量约15个拷贝的程度存在，而大质粒以每个染色体当量约1个拷贝的程度存在。这些质粒的生物学功能是未知的。
Previous nucleic acid association studies have identified at least nine deoxyribonucleic acid (DNA) homology classes of the Bacteroides fragilis group of organisms. Using these classes as a taxonomic framework, we have screened representative strains of the B. fragilis group for the presence of extrachromosomal (plasmid) DNA. [3H]thymidine-labeled cell lysates were subjected to sodium dodecyl sulfate-salt precipitation, and supernatant fractions from such preparations were analyzed using cesium chloride-ethidium bromide equilibrium centrifugation. One strain from each group was examined in this fashion. Five of the strains were judged to contain no detectable plasmid DNA; however, four strains were observed to yield satellite bands corresponding to covalently closed circular plasmid DNA. Plasmid DNA from such gradients was subjected to velocity sedimentation through both neutral and alkaline sucrose gradients to determine molecular size. A 23 X 10(6)-molecular-weight plasmid was found in a B. fragilis strain representing one DNA homology group of this species, whereas a 3 X 10(6)-molecular-weight plasmid was found in a B. fragilis strain representing a second homology group. Similarly, a 31 X 10(6)-molecular-weight plasmid was found in a Bacteroides thetaiotaomicron strain representing one DNA homology group of this species, whereas a 3 X 10(6)-molecular-weight plasmid was found in a B. thetaiotaomicron strain representing a second homology group. In all instances, the small-molecular weight plasmids were present to the extent of about 15 copies per chromosomal equivalent, whereas the large plasmids were present to the extent of approximately 1 copy per chromosomal equivalent. The biological function of these plasmids is unknown.