Abraham J M, Freitag C S, Gander R M, Clements J R, Thomas V L, Eisenstein B I
Mol Biol Med. 1986 Dec;3(6):495-508.
Having previously shown that the oscillating on-off expression (phase variation) of type 1 fimbriae in Escherichia coli is regulated genetically by an invertible element of DNA, we wished to determine whether E. coli isolates recovered from infected humans behaved in similar fashion. We examined four different clinical isolates that expressed type 1 fimbriae, P fimbriae, or both. Using, in Southern blot analysis, a DNA probe from the type 1 fimbrial switch, that hybridized to one DNA band from phase-on bacteria and to two DNA bands from phase-off bacteria, we found that the three clinical isolates expressing type 1 fimbriae contained the same invertible switch previously seen in the K-12 isolate. Employing a similar approach to characterize the on-off expression of P fimbriae, we used a DNA probe containing the known transcriptional signals for P fimbriae. Although we detected DNA rearrangement in the two strains expressing P fimbriae, unlike the case for type 1 fimbriae, the rearrangement did not correlate with the on-off state of the P fimbriae. Rather, the DNA rearrangement correlated with the environmental conditions of growth of the bacteria from which the DNA was isolated. These results confirm the notion that P fimbriae expression and type 1 fimbriae expression are controlled differently.
此前我们已表明，大肠杆菌1型菌毛的振荡式开关表达（相变）受DNA的一个可逆元件进行基因调控，我们希望确定从受感染人类身上分离出的大肠杆菌菌株是否有类似表现。我们检测了四种不同的临床分离株，它们表达1型菌毛、P菌毛或两者皆有。在Southern印迹分析中，我们使用来自1型菌毛开关的DNA探针，该探针与处于开启相细菌的一条DNA条带以及处于关闭相细菌的两条DNA条带杂交，我们发现，三种表达1型菌毛的临床分离株含有与K - 12分离株中先前发现的相同的可逆开关。采用类似方法来表征P菌毛的开关表达，我们使用了一个包含已知P菌毛转录信号的DNA探针。虽然我们在两种表达P菌毛的菌株中检测到了DNA重排，但与1型菌毛的情况不同，这种重排与P菌毛的开关状态无关。相反，DNA重排与分离出该DNA的细菌的生长环境条件相关。这些结果证实了P菌毛表达和1型菌毛表达受不同方式控制的观点。
