Setlow J K, Spikes D, Ledbetter M
J Bacteriol. 1984 Jun;158(3):872-7. doi: 10.1128/jb.158.3.872-877.1984.
Plasmids pNov1 and pNov1s , coding for resistance and sensitivity to novobiocin, respectively, were readily lost from wild-type Haemophilus influenzae but retained in a strain lacking an inducible defective prophage. The plasmid loss could be partly or wholly eliminated by a low-copy-number mutation in the plasmid or by the presence of certain antibiotic resistance markers in the host chromosome. Release of both phage HP1c1 , measured by plaque assay, and defective phage, measured by electron microscopy, was increased when the plasmids were present. The frequency of recombination between pNov1 and the chromosome, causing the plasmid to be converted to pNov1s , could under some circumstances be decreased from the normal 60 to 70% to below 10% by the presence of a kanamycin resistance marker in the chromosome. This suggested that a gene product coded for by the plasmid, the expression of which was affected by the kanamycin resistance marker, was responsible for the high recombination frequency. Evidence was obtained from in vitro experiments that the gene product was a gyrase.
分别编码对新生霉素耐药和敏感的质粒pNov1和pNov1s，很容易从野生型流感嗜血杆菌中丢失，但能保留在缺乏可诱导缺陷原噬菌体的菌株中。质粒的丢失可以通过质粒中的低拷贝数突变或宿主染色体中某些抗生素抗性标记的存在而部分或完全消除。当存在质粒时，通过噬菌斑测定法测定的噬菌体HP1c1和通过电子显微镜测定的缺陷噬菌体的释放均增加。在某些情况下，通过染色体中卡那霉素抗性标记的存在，pNov1与染色体之间的重组频率（导致质粒转化为pNov1s）可以从正常的60%至70%降低到10%以下。这表明质粒编码的一种基因产物（其表达受卡那霉素抗性标记的影响）是高重组频率的原因。从体外实验获得的证据表明该基因产物是一种解旋酶。
