Abraham J M, Freitag C S, Clements J R, Eisenstein B I
Proc Natl Acad Sci U S A. 1985 Sep;82(17):5724-7. doi: 10.1073/pnas.82.17.5724.
The expression of type 1 fimbriae (pili) of Escherichia coli is turned on and off at the transcriptional level at a high frequency (10(-3) per cell per generation) in a process termed phase variation. Using Southern blot and DNA sequence analysis, we have detected a genomic rearrangement in the switch region immediately upstream of the fimbrial structural gene. This rearrangement involves an invertible 314-base-pair segment of DNA whose alternating orientation apparently results in the on-and-off activation of a promoter that determines the state of fimbrial expression.
大肠杆菌1型菌毛的表达在转录水平上以高频率（每代每个细胞10⁻³）开启和关闭，这一过程称为相变。通过Southern印迹和DNA序列分析，我们在菌毛结构基因上游紧邻的开关区域检测到基因组重排。这种重排涉及一段314个碱基对的可逆DNA片段，其交替取向显然导致一个决定菌毛表达状态的启动子的开启和关闭激活。
