Benzinger R, Kleber I, Huskey R
J Gen Virol. 1978 Jun;39(3):531-5. doi: 10.1099/0022-1317-39-3-531.
High mol. wt. DNA was extracted from Escherichia coli lambda lysogens and was shown to be infectious. Its infectivity was due to prophage DNA integrated into the host chromosome rather than to DNA released from mature phage particles, as established by the following criteria: the titre of infectious DNA exceeded by 100-fold the titre of infectious units present before DNA extraction; mild shear selectively reduced prophage DNA infectivity to 2% of the unsheared DNA while lambda phage DNA infectivity retained 50% of its infectivity; DNA extracted from an E. coli (lambda c857 tsxisam6) lysogen yielded 200 times as many plaques on sup+ than on sup- spheroplasts. Thus lambda prophage DNA infectivity depends on expression of the excision gene while the infectivity of non-integrated forms of lambda does not. About 10(4) genome equivalents of E. coli DNA yielded one infectious centre unit in this assay system; this high infectivity should make prophage DNA a useful marker in genetic transformation experiments.
从大肠杆菌λ溶原菌中提取出高分子量DNA，并证明其具有感染性。其感染性源于整合到宿主染色体中的前噬菌体DNA，而非成熟噬菌体颗粒释放的DNA，这一点通过以下标准得以确立：感染性DNA的滴度比DNA提取前存在的感染单位滴度高出100倍；温和剪切可选择性地将前噬菌体DNA的感染性降低至未剪切DNA的2%，而λ噬菌体DNA的感染性则保留其感染性的50%；从大肠杆菌（λc857 tsxisam6）溶原菌中提取的DNA在sup +上产生的噬菌斑数量是在sup -原生质球上的200倍。因此，λ前噬菌体DNA的感染性取决于切除基因的表达，而λ非整合形式的感染性则不然。在该检测系统中，约10⁴个大肠杆菌DNA基因组当量产生一个感染中心单位；这种高感染性应使前噬菌体DNA成为遗传转化实验中的有用标记。
