Ogasawara N, Yoshikawa H
Department of Genetics, Osaka University Medical School, Suita, Japan.
Mol Microbiol. 1992 Mar;6(5):629-34. doi: 10.1111/j.1365-2958.1992.tb01510.x.
Genes and their organization are conserved in the replication origin region of the bacterial chromosome. To determine the extent of the conserved region in Gram-positive and Gram-negative bacteria, which diverged 1.2 billion years ago, we have further sequenced the region upstream from the dnaA genes in Bacillus subtilis and Pseudomonas putida. Fifteen open reading frames (ORFs) and 11 ORFs were identified in the 13.6 kb and the 9.8 kb fragments in B. subtilis and P. putida, respectively. Eight consecutive P. putida genes, except for one small ORF (homologous to gene 9K of Escherichia coli) in between, are homologous in sequence and relative locations to genes in B. subtilis. Altogether, 12 genes and their organization are conserved in B. subtilis and P. putida in the origin region. We found that the conserved region terminated on one side after the orf290 in P. putida (orf282 in B. subtilis). In the B. subtilis chromosome, five additional ORFs were found in between the conserved genes, suggesting that they are added after Gram-positive bacteria were diverged from the Gram-negative bacteria. One of the ORFs is a duplicate of the conserved gene. The third non-translatable region containing multiple repeats of DnaA-box (second in the case of P. putida) was found flanking gidA in both organisms. This result shows clearly that E. coli oriC and flanking genes gidA and gidB have been translocated by the inversion of some 40 kb fragment.
基因及其组织在细菌染色体的复制起始区域是保守的。为了确定在12亿年前分化的革兰氏阳性菌和革兰氏阴性菌中保守区域的范围，我们进一步对枯草芽孢杆菌和恶臭假单胞菌中dnaA基因上游的区域进行了测序。在枯草芽孢杆菌的13.6 kb片段和恶臭假单胞菌的9.8 kb片段中分别鉴定出15个开放阅读框（ORF）和11个ORF。除了中间一个小的ORF（与大肠杆菌的9K基因同源）外，恶臭假单胞菌的8个连续基因在序列和相对位置上与枯草芽孢杆菌中的基因同源。在起始区域，枯草芽孢杆菌和恶臭假单胞菌总共12个基因及其组织是保守的。我们发现保守区域在恶臭假单胞菌的orf290（枯草芽孢杆菌中的orf282）之后在一侧终止。在枯草芽孢杆菌染色体中，在保守基因之间发现了另外5个ORF，这表明它们是在革兰氏阳性菌与革兰氏阴性菌分化之后添加的。其中一个ORF是保守基因的重复。在两种生物中，都发现第三个包含多个DnaA框重复序列的非翻译区域（恶臭假单胞菌中是第二个）位于gidA侧翼。这一结果清楚地表明，大肠杆菌oriC及其侧翼基因gidA和gidB通过约40 kb片段的倒位而发生了易位。
