Johnson E M, Placek B P, Snellings N J, Baron L S
J Bacteriol. 1975 Jul;123(1):1-6. doi: 10.1128/jb.123.1.1-6.1975.
A partially diploid Escherichia coli hybrid recovered from mating with a Salmonella typhimurium donor was converted to an Hfr strain, designated WR2080, as a means to examine the manner in which the added Salmonella genetic material was conserved in it. The Salmonella argH-+, metB-+, and RHA-+ alleles contained as supernumerary genes in WR2080 were transferred together to E. coli recipients in interrupted mating experiments approximately 25 min after initial parental contact; transfer of the allelic E. coli genes by a haploid Hfr of the same transfer orientation occurred between 23.5 min (argH-+) and 25 min (rha-+) after initial contact. Entry of the E. coli ilv-+ marker of WR2080 in these experiments occurred at 29.5 min, 1.5 min later than the entry time of this marker from the haploid E. coli Hfr. When unselected inheritance of the recessive E. coli argH-minus and rha-minus alleles of WR2080 was examined among ilv-+ selected E. coli recipients in which unselected inheritance of the Salmonella donor genes was shown to be low (8%), inheritance of argH-minus was only 7%, whereas 51% inherited the neighboring rha-minus gene. In a comparative cross employing a haploid E. coli Hfr, in which rha inheritance was similar at 56%, argH inheritance was 41%. It was concluded that the Salmonella genes contained in WR2080 were conserved on a genetic segment about 1.5 min in length chromosomally inserted near the allelic E. coli genes, thus creating a duplication on that region within the hybrid chromosome.
从与鼠伤寒沙门氏菌供体交配后获得的部分二倍体大肠杆菌杂种被转化为一个高频重组（Hfr）菌株，命名为WR2080，以此作为一种手段来研究添加的沙门氏菌遗传物质在其中的保存方式。在中断杂交实验中，WR2080中作为额外基因包含的沙门氏菌argH⁺、metB⁺和RHA⁺等位基因在亲本最初接触后约25分钟一起转移到大肠杆菌受体中；具有相同转移方向的单倍体Hfr对大肠杆菌等位基因的转移在最初接触后23.5分钟（argH⁺）至25分钟（rha⁺）之间发生。在这些实验中，WR2080的大肠杆菌ilv⁺标记在29.5分钟进入，比该标记从单倍体大肠杆菌Hfr进入的时间晚1.5分钟。当在ilv⁺选择的大肠杆菌受体中检测WR2080的隐性大肠杆菌argH⁻和rha⁻等位基因的非选择遗传时，其中沙门氏菌供体基因的非选择遗传率较低（8%），argH⁻的遗传率仅为7%，而51%的受体遗传了相邻的rha⁻基因。在一个使用单倍体大肠杆菌Hfr的比较杂交中，rha的遗传率相似，为56%，argH的遗传率为41%。得出的结论是，WR2080中包含的沙门氏菌基因在一个长度约为1.5分钟的遗传片段上得以保存，该片段在染色体上插入到等位大肠杆菌基因附近，从而在杂种染色体内的该区域产生了重复。
