Conjugal transfer of a virulence plasmid in the opportunistic intracellular actinomycete Rhodococcus equi.
Conjugal transfer of a virulence plasmid in the opportunistic intracellular actinomycete Rhodococcus equi.
复制标题
机会性细胞内放线菌马红球菌中毒力质粒的接合转移。
DOI：
10.1128/jb.01210-12
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发表时间：
2012
影响因子：
3.2
通讯作者：
Hondalus,MK
中科院分区：
文献类型：
--
作者：
Tripathi,VN;Harding,WC;Willingham-Lane,JM;Hondalus,MK
马红球菌是一种兼性细胞内、革兰氏阳性、土传放线菌，可在幼马（马驹）和免疫功能低下的人（例如艾滋病患者）中引起严重的化脓性肉芽肿性肺炎并伴有脓肿。从马驹中分离出来的所有马系马菌株，以及从人类中分离出来的大约三分之一的马马马菌株都含有一个约81-kb的大质粒，该质粒对于生物体的巨噬细胞内生长以及马驹和鼠体内模型系统中的毒力至关重要。我们发现，整个毒力质粒可以以高频率从含质粒的马系病毒菌株（供体）转移到不含质粒的马系病毒菌株（受体），并且质粒传输重建了巨噬细胞的细胞内生长能力。质粒转移需要活细胞和细胞间接触，并且不受 DNase 存在的影响，这些因素表明接合是遗传转移的主要手段。删除假定的松弛酶编码基因 traA（位于质粒的拟议接合区域），废除了质粒转移。 thetra突变的逆转恢复了质粒的可传播性。最后，证明了质粒向其他红球菌属物种和一些其他相关生物体的传播。这是第一项显示毒力质粒在马罗氏菌中转移的研究，它建立了毒力质粒在土壤细菌之间移动的机制。
Rhodococcus equi is a facultative intracellular, Gram-positive, soilborne actinomycete which can cause severe pyogranulomatous pneumonia with abscessation in young horses (foals) and in immunocompromised people, such as persons with AIDS. All strains of R. equi isolated from foals and approximately a third isolated from humans contain a large, ∼81-kb plasmid which is essential for the intramacrophage growth of the organism and for virulence in foals and murinein vivomodel systems. We found that the entire virulence plasmid could be transferred from plasmid-containing strains of R. equi (donor) to plasmid-free R. equi strains (recipient) at a high frequency and that plasmid transmission reestablished the capacity for intracellular growth in macrophages. Plasmid transfer required living cells and cell-to-cell contact and was unaffected by the presence of DNase, factors pointing to conjugation as the major means of genetic transfer. Deletion of a putative relaxase-encoding gene,traA, located in the proposed conjugative region of the plasmid, abolished plasmid transfer. Reversion of thetraAmutation restored plasmid transmissibility. Finally, plasmid transmission to other Rhodococcus species and some additional related organisms was demonstrated. This is the first study showing a virulence plasmid transfer in R. equi, and it establishes a mechanism by which the virulence plasmid can move among bacteria in the soil.