Eckerson H W, Reynard A M
J Bacteriol. 1977 Jan;129(1):131-7. doi: 10.1128/jb.129.1.131-137.1977.
Mating aggregates during conjugation directed by an F-like R factor in Escherichia coli were measured as the number of Lac+-Lac- sectored colonies present in a mating mixture. There is a high degree of correlation between the concentration of transconjugants produced in a mating mixture and the concentration of mating aggregates observed at several different concentrations of donor and recipient cells. The mating aggregates are sex pilus specific as demonstrated by the ability of donor-specific ribonucleic acid phage MS-2 to decrease both mating aggregates and transconjugants in a mating mixture. During entry exclusion by either a derepressed or a repressed F-like R factor, isogenic to the superinfecting R factor except for a resistance determinant, the number of transconjugants was markedly reduced, but the number of mating aggregates was not decreased. Entry exclusion by F-Gal toward the donor HfrH resembled that of the F-like R factor in that there was a reduction in the number of recombinants but no significant decrease in mating aggregates. These results suggest that entry exclusion inhibits conjugation at a stage after the formation of mating aggregates.
在大肠杆菌中，由F类R因子指导的接合过程中的交配聚集体通过交配混合物中出现的Lac⁺-Lac⁻扇形菌落数量来测定。在几种不同浓度的供体细胞和受体细胞条件下，交配混合物中产生的转接合子浓度与观察到的交配聚集体浓度之间存在高度相关性。如供体特异性核糖核酸噬菌体MS-2能够降低交配混合物中的交配聚集体和转接合子数量所示，交配聚集体具有性菌毛特异性。在由与超感染R因子同基因（除抗性决定簇外）的去阻遏或阻遏的F类R因子进行的进入排斥过程中，转接合子数量显著减少，但交配聚集体数量并未减少。F-Gal对供体HfrH的进入排斥与F类R因子的相似，即重组体数量减少，但交配聚集体数量无显著下降。这些结果表明，进入排斥在交配聚集体形成后的阶段抑制接合。
