Ogawa H I, Tolle C L, Summers A O
Gene. 1984 Dec;32(3):311-20. doi: 10.1016/0378-1119(84)90006-4.
Tn7 insertion mutagenesis has been used to facilitate the generation of a physical (restriction endonuclease) and genetic map of the IncM plasmid, R831b. The only selectable phenotypes carried by this 90-kb conjugative plasmid are resistances to inorganic mercury [Hg(II)] and to organomercury compounds. Mutants in the Hgr locus of R831b complemented previously described mutants in the mer operon of the IncFII plasmid R100, indicating functional homology of the locus in each of these different plasmids. However, the R831b Hgr locus is not notably similar in restriction site pattern to either the mer operon of R100 or the mercury resistance transposon, Tn501. Although the enzymes they encode are co-ordinately regulated, the Omr locus of R831b maps approx. 13.5 kb away from the Hgr locus. Three insertions which affect neither phenotype lie between the Hgr and Omr loci; thus, the loci are separated both physically and genetically. One mutant was obtained which tentatively identifies the position of the Tra locus of R831b as adjacent to the Hgr locus.
Tn7插入诱变已被用于辅助构建IncM质粒R831b的物理（限制性内切酶）图谱和遗传图谱。这个90 kb的接合性质粒携带的唯一可选择表型是对无机汞[Hg(II)]和有机汞化合物的抗性。R831b的Hgr位点中的突变体可互补先前描述的IncFII质粒R100的mer操纵子中的突变体，这表明这些不同质粒中该位点具有功能同源性。然而，R831b的Hgr位点在限制性酶切位点模式上与R100的mer操纵子或汞抗性转座子Tn501均无明显相似性。虽然它们编码的酶受到协同调控，但R831b的Omr位点在图谱上距离Hgr位点约13.5 kb。有三个插入突变不影响任何一种表型，位于Hgr和Omr位点之间；因此，这两个位点在物理和遗传上都是分开的。获得了一个突变体，初步确定R831b的Tra位点位置与Hgr位点相邻。
