Cheetham B F, Katz M E
Department of Molecular and Cell Biology, University of New England, Armidale, New South Wales, Australia.
Mol Microbiol. 1995 Oct;18(2):201-8. doi: 10.1111/j.1365-2958.1995.mmi_18020201.x.
A virulence-associated region in the genome of Dichelobacter nodosus has been shown to contain an integrase gene which is highly related to the integrases of Shigella flexneri phage Sf6 and coliphages P4 and phi R73, together with open reading frames (vapB, C and D) related to genes borne on plasmids in Neisseria gonorrhoeae, Escherichia coli, Actinobacillus actinomycetemcomitans and Treponema denticola. Similar to P4 and phi R73, the vap region is bracketed by putative bacteriophage att sites and is adjacent to a tRNA gene, which suggests that the vap region has been derived by the integration of a bacteriophage, or a plasmid carrying a bacteriophage-related integrase gene. Many similarities in genes and genes clusters encoding virulence determinants have been found in distantly related bacteria. These genes are often located on plasmids in one organism but on the chromosome in others, implying that transmission of the genes has been followed by integration. Thus, the events which have generated the vap regions of D. nodosus may represent a common mechanism for transfer of virulence determinants. A number of genes involved in the virulence of bacterial pathogens are found on integrated bacteriophages, and we suggest that others will prove to be associated with tRNA genes and/or integrase genes derived from bacteriophages. The use of tRNA genes as integration sites for many bacteriophages and plasmids may favour intergeneric transmission, as tRNA genes are highly conserved.
已证明结节拟杆菌基因组中的一个毒力相关区域含有一个整合酶基因，该基因与福氏志贺氏菌噬菌体Sf6以及大肠杆菌噬菌体P4和φR73的整合酶高度相关，还含有与淋病奈瑟氏菌、大肠杆菌、伴放线放线杆菌和齿垢密螺旋体中质粒携带的基因相关的开放阅读框（vapB、C和D）。与P4和φR73相似，vap区域两侧为假定的噬菌体附着位点，且与一个tRNA基因相邻，这表明vap区域是通过噬菌体或携带噬菌体相关整合酶基因的质粒整合而来。在远缘细菌中发现了许多编码毒力决定因素的基因和基因簇存在相似性。这些基因在一种生物体中通常位于质粒上，而在其他生物体中则位于染色体上，这意味着基因在传播后发生了整合。因此，产生结节拟杆菌vap区域的事件可能代表了毒力决定因素转移的一种常见机制。许多参与细菌病原体毒力的基因存在于整合的噬菌体上，我们认为其他基因也将被证明与源自噬菌体的tRNA基因和/或整合酶基因有关。由于tRNA基因高度保守，将tRNA基因用作许多噬菌体和质粒的整合位点可能有利于属间传播。
