Wanner B L
J Bacteriol. 1986 Dec;168(3):1366-71. doi: 10.1128/jb.168.3.1366-1371.1986.
Several phoR alleles (phoR19, phoR20, phoR68, phoR69, phoR70, and phoR78) led to either a bacterial alkaline phosphatase (BAP)-constitutive phenotype or a variable behavior, depending upon the strain tested. Whereas Escherichia coli K10, MC1000, and XPh4 phoR mutants were constitutive, AB1157, BD792, MC4100, and W3110 phoR mutants displayed the metastable character. For the latter strains, constitutive mutants regularly segregated BAP-negative clones which yielded constitutive variants again at a high frequency. Indeed, the pattern of variation observed in BAP-variable phoR strains is phenotypically analogous to phase variation of the H1/H2 flagellum antigen type in Salmonella typhimurium and the molecular switch between the immune and sensitive states in bacteriophage lambda. The metastable behavior was not a general property of BAP-constitutive mutants, since several phosphate-specific transport-phoU mutations led to a constitutive (stable) phenotype regardless of the strain tested. But in phoR phosphate-specific transport-phoU mutants, the metastable character was epistatic (dominant), and such double mutants showed clonal variation in BAP-variable strains.
几个phoR等位基因（phoR19、phoR20、phoR68、phoR69、phoR70和phoR78）导致了细菌碱性磷酸酶（BAP）组成型表型或可变行为，这取决于所测试的菌株。大肠杆菌K10、MC1000和XPh4的phoR突变体表现为组成型，而AB1157、BD792、MC4100和W3110的phoR突变体则表现出亚稳定特性。对于后几种菌株，组成型突变体经常分离出BAP阴性克隆，这些克隆又会以高频率再次产生组成型变体。实际上，在BAP可变的phoR菌株中观察到的变异模式在表型上类似于鼠伤寒沙门氏菌中H1/H2鞭毛抗原类型的相变以及噬菌体λ中免疫状态和敏感状态之间的分子开关。亚稳定行为并非BAP组成型突变体的普遍特性，因为几个磷酸盐特异性转运phoU突变导致了组成型（稳定）表型，而与所测试的菌株无关。但是在phoR磷酸盐特异性转运phoU突变体中，亚稳定特性是上位性的（显性的），并且这种双突变体在BAP可变菌株中表现出克隆变异。
