Nishioka Y, Eisenstark A
J Bacteriol. 1970 May;102(2):320-33. doi: 10.1128/jb.102.2.320-333.1970.
5-Bromouracil (BU) was pulsed into the genome of synchronously growing cells of an F(-) strain of Salmonella typhimurium of LT2. BU-labeled genes were transduced with P22 phage to a series of recipient auxotrophs. When BU was incorporated early in the replication cycle, the transducing markers that had hybrid densities were those that lie between 9 and 12 o'clock on the genetic map. When BU was incorporated during the terminal period of the synchronous cycle, the transducing particles had hybrid densities for genes that lie from 1 to 8 o'clock clockwise. When phages were prepared on cells in which the middle period was BU-labeled, transducing particles with hybrid densities appeared for genes that lie in two separate regions: between 7 and 9 o'clock and between 12 and 2 o'clock. Analysis of the map sequences of the transduced BU genes, the relative frequency of transduction for each marker, and the time sequence of replication led to a hypothesis that the origin of replication is near the isoleucine-valine gene on the chromosome map. As for direction of replication, several models were considered, including the possibility that replication may proceed in both directions in the same chromosome. It was also found that the aroB, cysG, and strA genes are cotransduced and strA and aroC are also cotransduced. The relative order of the four genes was found to be aroB, cysG, strA, aroC, but the orientation in the circular map was not determined.
5-溴尿嘧啶（BU）被脉冲导入鼠伤寒沙门氏菌LT2 F(-)菌株同步生长细胞的基因组中。用P22噬菌体将带有BU标记的基因转导至一系列受体营养缺陷型菌株。当BU在复制周期早期掺入时，具有杂交密度的转导标记是那些位于遗传图谱上9点至12点之间的标记。当BU在同步周期的末期掺入时，转导颗粒对顺时针方向从1点至8点的基因具有杂交密度。当在中期用BU标记的细胞上制备噬菌体时，具有杂交密度的转导颗粒出现在两个不同区域的基因中：7点至9点之间和12点至2点之间。对转导的BU基因的图谱序列、每个标记的相对转导频率以及复制的时间序列进行分析后得出一个假设，即复制起点在染色体图谱上异亮氨酸-缬氨酸基因附近。至于复制方向，考虑了几种模型，包括在同一染色体上复制可能双向进行的可能性。还发现aroB、cysG和strA基因共转导，strA和aroC也共转导。发现这四个基因的相对顺序是aroB、cysG、strA、aroC，但在环状图谱中的方向未确定。
