Bergquist P L, Adelberg E A
J Bacteriol. 1972 Jul;111(1):119-28. doi: 10.1128/jb.111.1.119-128.1972.
PB15 is an Hfr strain of Escherichia coli K-12. It arose from an F' strain carrying a temperature-sensitive F-gal by an event which blocked the detachment of F-gal in the normally reversible integration process. In PB15, the detachment of F-gal by a second mechanism can now be detected: this mechanism results in the excision and transfer of extended chromosomal segments which include the integrated F-gal; the excised segments are inferred to have circularized. Their excision, which is independent of the recA(+) allele, occurs at an unusually high rate during conjugation; a mutant F-initiator protein is suggested as the cause of this phenomenon. After their establishment in recipients, the enlarged F-genotes undergo further deletions of included donor genes by a process which is again recA(+)-independent. In Rec(+), but not in Rec(-), cells, a high proportion of the deleted fragments are rescued by integration into the recipient's chromosome.
PB15是大肠杆菌K-12的一个高频重组（Hfr）菌株。它起源于一个携带温度敏感型F因子（F-gal）的F'菌株，是由一个在正常可逆整合过程中阻止F-gal分离的事件产生的。在PB15中，现在可以检测到通过第二种机制导致的F-gal分离：这种机制导致包括整合的F-gal在内的染色体延伸片段的切除和转移；推断切除的片段已经环化。它们的切除独立于recA(+)等位基因，在接合过程中以异常高的频率发生；推测一种突变的F起始蛋白是这种现象的原因。在它们进入受体细胞后，扩大的F基因组通过一个同样独立于recA(+)的过程进一步缺失所含的供体基因。在Rec(+)细胞而非Rec(-)细胞中，很大一部分缺失片段通过整合到受体染色体中而被挽救。
