Salazar L, Fsihi H, de Rossi E, Riccardi G, Rios C, Cole S T, Takiff H E
Laboratorio de Genética Molecular, Instituto Venezolano de Investigaciones Científicas (IVIC), Caracas, Venezuela.
Mol Microbiol. 1996 Apr;20(2):283-93. doi: 10.1111/j.1365-2958.1996.tb02617.x.
The genus Mycobacterium is composed of species with widely differing growth rates ranging from approximately three hours in Mycobacterium smegmatis to two weeks in Mycobacterium leprae. As DNA replication is coupled to cell duplication, it may be regulated by common mechanisms. The chromosomal regions surrounding the origins of DNA replication from M. smegmatis, M. tuberculosis, and M. leprae have been sequenced, and show very few differences. The gene order, rnpA-rpmH-dnaA-dnaN-recF-orf-gyrB-gyrA, is the same as in other Gram-positive organisms. Although the general organization in M. smegmatis is very similar to that of Streptomyces spp., a closely related genus, M. tuberculosis and M. leprae differ as they lack an open reading frame, between dnaN and recF, which is similar to the gnd gene of Escherichia coli. Within the three mycobacterial species, there is extensive sequence conservation in the intergenic regions flanking dnaA, but more variation from the consensus DnaA box sequence was seen than in other bacteria. By means of subcloning experiments, the putative chromosomal origin of replication of M. smegmatis, containing the dnaA-dnaN region, was shown to promote autonomous replication in M. smegmatis, unlike the corresponding regions from M. tuberculosis or M. leprae.
分枝杆菌属由生长速率差异很大的菌种组成，从耻垢分枝杆菌约三小时到麻风分枝杆菌两周不等。由于DNA复制与细胞复制相关联，它可能受共同机制调控。耻垢分枝杆菌、结核分枝杆菌和麻风分枝杆菌DNA复制起始位点周围的染色体区域已测序，显示差异极小。基因顺序rnpA-rpmH-dnaA-dnaN-recF-orf-gyrB-gyrA与其他革兰氏阳性菌相同。尽管耻垢分枝杆菌的总体结构与密切相关的链霉菌属非常相似，但结核分枝杆菌和麻风分枝杆菌有所不同，因为它们在dnaN和recF之间缺少一个与大肠杆菌gnd基因相似的开放阅读框。在这三种分枝杆菌菌种中，dnaA侧翼基因间区域存在广泛的序列保守性，但与其他细菌相比，从共有DnaA框序列中观察到的变异更多。通过亚克隆实验表明，含有dnaA-dnaN区域的耻垢分枝杆菌假定染色体复制起始位点可促进耻垢分枝杆菌中的自主复制，这与结核分枝杆菌或麻风分枝杆菌的相应区域不同。
