变铅青链霉菌对噬菌体φHAU3抗性与异常修饰之间的相互关系

STUDIES ON THE INTERACTION BETWEEN HAU3-RESISTANCE AND UNUSUAL MODIFICATION OF STREPTOMYCES LIVIDANS

变铅青链霉菌异常修饰突变菌株ＺＸｌ同时丧失了对噬菌体ＨＡＵ３的抗性，遗传学杂交结果揭示，ＤＮＡ降解和对ＨＡＵ３抗性这两种表型从不发生分离。以ＺＸｌ为宿主和链霉菌低拷贝质粒ＳＣＰ２衍生的载体ｐＩＪ９２２为载体，构建了变铅青链霉菌ＪＴ４６的基因组文库。在８０００多个转化子中获得了一个能使ＺＸ１对ＨＡＵ３显示抗性的杂合质粒，命名为ｐＩＪ８３１０。它除了含有完整的ｐＩＪ９２２外，还携带了大约１１ｋｂ的外源片段。Ｓｏｕｔｈｅｒｎ杂交证实，这个外源片段来源于ＪＴ４６，但在ＺＸ１中完全消失。利用转座子Ｔｎ４５６０对该克隆进行诱变定位，获得了中断噬菌体抗性基因表达的衍生质粒，并已证实Ｔｎ４５６０插入在一个２．５ｋｂ的ＢｄｍＨＩ一ＥｃｏＲＩ片段上。

he unusual modification deficient mutant of Streptomyces lividans, ZX1, lost phage resis-tance to HAU3. The gene responsible for the DNA degradation and for HAU3 resistanceare genetically linked. Genomic library of Streptomyces lividans JT46 was constructed inlow-copy number plasmid pIJ922(SCP2* derivative). Only one out of 8,000 transformants thatconfers HAU3￣R on ZX1 was obtained and was designated as pIJ8310 contains an 11kb in-sert on BamHI site of entire pIJ922. Southem blot hybridization indicated that the HAU3 re-sistance fragment responsible for HAU3 resistance comes from JT46, but was completely de-leted from ZX1. Mutagenesis of pIJ8310 with transposon Tn4560 produas pIJ8311, which nolonger confers HAU3 resistance. The site of the transposon insertion was mapped on the2.5kb BamHI-EcoRI fragment of pIJ8310.