Analysis of sequences flanking the vap regions of Dichelobacter nodosus: Evidence for multiple integration events, a killer system, and a new genetic element
Analysis of sequences flanking the vap regions of Dichelobacter nodosus: Evidence for multiple integration events, a killer system, and a new genetic element
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DOI：
10.1099/00221287-143-2-553
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发表时间：
1997-02-01
期刊：
影响因子：
--
通讯作者：
Cheetham, BF
中科院分区：
文献类型：
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作者：
Bloomfield, GA;Whittle, G;Cheetham, BF
结节双歧杆菌是引起羊蹄疾的病原体。节纹夜蛾基因组中的vap区可能是由于遗传因素的整合而产生的，并可能在毒力中起作用。强毒菌株A198的vap区有多个拷贝。本研究通过Southern杂交和DNA测序分析了A198株vap区1、2和3左右的序列。结果表明，VAP区1和2是由不同tRNA基因的独立整合事件引起的。发现了第二整合酶基因(IntB)，与噬菌体抑制蛋白(RegA)相似的基因，以及与接合转座子(GepA)的ORF相似的基因。这表明，第二个遗传元件，要么是噬菌体，要么是接合转座子，被整合到结球拟青霉基因组中vap区域3的旁边。用Southern印迹和聚合酶链式反应分析了其他3株强毒株和1株良性株的intB和vap区的排列。一株菌株H1215含有VAPE‘而不含有VAPE，因此与VAP区3相似，表明VAP区3也可能是由独立的整合事件引起的。在所有菌株中，在vap区旁边发现了一份Lot副本。VAP区包含两个基因，VapA和ToxA，与杀手质粒RTS1的hig基因相似。有证据表明，VapA和ToxA在结节跳甲中具有类似的功能。
Dichelobacter nodosus is the causative agent of ovine footrot. The vap regions of the D. nodosus genome may have arisen by the integration of a genetic element and may have a role in virulence. The virulent D. nodosus strain A198 has multiple copies of the vap regions. In the present study, sequences to the left and right of vap regions 1, 2 and 3 of strain A198 were analysed by Southern blotting and DNA sequencing. The results suggest that vap regions 1 and 2 arose by independent integration events into different tRNA genes. The discovery of a second integrase gene (intB), a gene with similarity to bacteriophage repressor proteins (regA), and a gene similar to an ORF from a conjugative transposon (gepA). suggests that a second genetic element, either a bacteriophage or a conjugative transposon, is integrated next to vap region 3 in the D. nodosus genome. The arrangement of intB and the vap regions in three other virulent strains and one benign strain was determined using using Southern blotting and PCR. One strain, H1215, contained vapE' and not vapE, and thus resembles vap region 3, suggesting that vap region 3 also may have arisen by an independent integration event. In all strains, a copy of lots was found next to the vap regions. The vap regions contain two genes, vapA and toxA, with similarity to the hig genes of the killer plasmid Rts1. Evidence is presented that vapA and toxA have a similar function in D. nodosus.