Laity C, Chater K F, Lewis C G, Buttner M J
John Innes Institute, John Innes Centre, Norwich, UK.
Mol Microbiol. 1993 Jan;7(2):329-36. doi: 10.1111/j.1365-2958.1993.tb01124.x.
The phage growth limitation (Pgl) system of Streptomyces coelicolor A3(2) was shown to be specific to phi C31 homo-immune phages, and to be absent from the closely related strain Streptomyces lividans. A 16 kb fragment of S. coelicolor A3(2) DNA was isolated which complemented the Pgl- phenotype of J1501, a pgl mutant derivative of the Pglts S. coelicolor strain M130. The cloned DNA complemented only half of the available pgl mutants, which therefore represented at least two groups, designated Pgl class A and class B strains. It follows that more than one kind of high-frequency genetic event can lead to the Pgl- phenotype. Crosses between class A and class B strains yielded high frequencies of Pgl+ recombinants. Crosses between strains of the same class gave no Pgl+ recombinants. The cloned DNA was altered by deletion or apparent point mutation upon passage through the two class B strains tested, such that it was no longer capable of complementing class A strains. This accumulation of mutations might suggest that the expression of the cloned DNA is toxic to at least some class B strains. The nature of the genetic instability associated with the Pgl system was not detectable by Southern blot analysis.
天蓝色链霉菌A3(2)的噬菌体生长限制（Pgl）系统被证明对φC31同免疫噬菌体具有特异性，并且在密切相关的菌株浅青紫链霉菌中不存在。分离出了天蓝色链霉菌A3(2) DNA的一个16 kb片段，该片段可互补J1501的Pgl-表型，J1501是Pglts天蓝色链霉菌菌株M130的pgl突变衍生物。克隆的DNA仅互补了一半可用的pgl突变体，因此这些突变体至少代表两组，分别命名为Pgl A类和B类菌株。由此可见，不止一种高频遗传事件可导致Pgl-表型。A类和B类菌株之间的杂交产生了高频率的Pgl+重组体。同一类菌株之间的杂交未产生Pgl+重组体。在通过测试的两个B类菌株传代后，克隆的DNA因缺失或明显的点突变而发生改变，以至于它不再能够互补A类菌株。这种突变的积累可能表明克隆DNA的表达对至少一些B类菌株有毒性。通过Southern印迹分析无法检测到与Pgl系统相关的遗传不稳定性的性质。
