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首页> 外文期刊>Journal of bacteriology >Distribution of Tn551 insertion sites responsible for auxotrophy on the Staphylococcus aureus chromosome.
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Distribution of Tn551 insertion sites responsible for auxotrophy on the Staphylococcus aureus chromosome.

机译：Tn551插入位点的分布负责金黄色葡萄球菌染色体上的营养缺陷。

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A method was devised to efficiently select isolates of Staphylococcus aureus 8325 in which Tn551, a transposon originating on the pI258 plasmid responsible for erythromycin resistance (Emr), had translocated to the host chromosome. This method consisted of selecting for Emr at 43 degrees C with a strain in which the pI258 plasmid was unable to replicate at 43 degrees C because of a temperature-sensitive plasmid mutation. By selecting isolates that were Emr at 43 degrees C and auxotrophic for nutrients not required by the parent strain. Tn551-induced auxotrophic mutants were readily isolated. The incidence of auxotrophic classes was not random; 80% of the isolates in one experiment were Trp-, whereas only a single example of each of some of the other classes was isolated. Among the Trp- mutants, the distribution of trp genes affected and the frequency of precise excision of Tn551 from individual sites varied. When analyzed by transformation, the Tn551-induced ala, his, ilv, lys, rib, thrA, thrB, and trp mutations were shown to occupy sites previously defined by nitrosoguanidine-induced mutations. Tn551-induced mutagenesis provided three previously unrecognized classes of auxotrophs (tyr, met, and thrC), and the Tn551 integration sites resulting in these mutations have been identified. In addition, a chromosomal region (uraB) was identified by Tn551 mutagenesis that is distinct from uraA (previously defined by chemical mutagenesis). Some Tn551-induced mutations (most notably pur) could not be linked to the known linkage groups of the chromosome by transformation. With the exception of two pur mutations, all of the Tn551-induced auxotrophic mutational sites cotransformed at unity with Tn551 and, in cases in which they were selected, prototrophic transformants were always Ems. Thus, the Tn551 and auxotrophic sites are identical.
机译：设计了一种方法来有效地选择金黄色葡萄球菌8325的分离株，其中Tn551（起源于负责红霉素抗性（Emr）的pI258质粒的转座子）已转移到宿主染色体上。该方法包括用一种菌株选择43℃下的Emr，在该菌株中，由于温度敏感性质粒突变，pI258质粒不能在43℃下复制。通过选择在43摄氏度下为Emr且营养缺陷型的分离株，以获得亲本菌株不需要的营养。 Tn551诱导的营养缺陷型突变体易于分离。营养缺陷型的发生率不是随机的。在一个实验中，有80％的分离株是Trp-，而在其他一些分类中，只有一个分离出了一个例子。在Trp突变体中，受影响的trp基因的分布以及从单个位点精确切除Tn551的频率各不相同。通过转化分析时，显示Tn551诱导的ala，his，ilv，lys，rib，thrA，thrB和trp突变占据了亚硝基胍诱导的突变先前定义的位点。 Tn551诱导的诱变提供了三种以前无法识别的营养缺陷型（tyr，met和thrC），并且已经鉴定出导致这些突变的Tn551整合位点。另外，通过Tn551诱变鉴定了与uraA不同的染色体区域（uraB）（先前由化学诱变定义）。一些Tn551诱导的突变（最明显的是pur突变）无法通过转化与染色体的已知连锁群相连。除两个pur突变外，所有Tn551诱导的营养缺陷型突变位点都与Tn551一起共转化，并且在选择它们的情况下，原生营养型转化子始终为Ems。因此，Tn551和营养缺陷位点是相同的。

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