Brown N L, Parish J H
J Gen Microbiol. 1976 Mar;93(1):63-8. doi: 10.1099/00221287-93-1-63.
The presence of extrachromosomal DNA in strains of Myxococcus xanthus and M fulvus was examined by rate-zonal centrifugation of radioactively-labelled DNA in 'cleared lysates'. All the strains examined contained extrachromosomal DNA, with the exception of M. xanthus FBt. Chloramphenicol resistance is inducible in M. xanthus FBt. A peak of extrachromosomal DNA, containing covalently closed molecules, was found in one of the induced strains, implying that induction of chloramphenicol resistance is associated with the production of a plasmid. By incubating R+ strains of Escherichia coli with myxococci, R factor-mediated chloramphenicol resistance can be introduced into the latter. Evidence of extra chromosomal DNA in a derivative of M. xanthus with chloramphenicol resistance from R factor RI. 19 unique to the chloramphenicol strain, was obtained. By using a double-labelling technique, several chloramphenicol-resistant strains of M. fulvus M were examined. Evidence for a peak, unique for the chloramphenicol-resistant strain, was found in a strain with resistance derived from the R factor, S-a, but not from comparable strains with resistance derived from R factors R57b, R1. 19 and R478.
通过对“澄清裂解物”中放射性标记的DNA进行速率区带离心，检测了黄色粘球菌和富黄粘球菌菌株中染色体外DNA的存在情况。除黄色粘球菌FBt外，所有检测的菌株都含有染色体外DNA。黄色粘球菌FBt中的氯霉素抗性是可诱导的。在其中一个诱导菌株中发现了一个含有共价闭合分子的染色体外DNA峰，这意味着氯霉素抗性的诱导与质粒的产生有关。通过将大肠杆菌的R⁺菌株与粘球菌一起培养，可以将R因子介导的氯霉素抗性引入后者。获得了来自R因子RI.19的具有氯霉素抗性的黄色粘球菌衍生物中存在染色体外DNA的证据，该证据是氯霉素菌株所特有的。通过使用双标记技术，检测了富黄粘球菌M的几个氯霉素抗性菌株。在一个具有源自R因子S-a抗性的菌株中发现了一个对氯霉素抗性菌株独特的峰的证据，但在具有源自R因子R57b、R1.19和R478抗性的可比菌株中未发现。
