A genomic islet mediates flagellar phase variation in Escherichia coli strains carrying the flagellin-specifying locus flk
A genomic islet mediates flagellar phase variation in Escherichia coli strains carrying the flagellin-specifying locus flk
复制标题
基因组胰岛介导携带鞭毛蛋白特异性基因座 flk 的大肠杆菌菌株中的鞭毛相位变异
DOI：
10.1128/jb.01937-07
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发表时间：
2008-07-01
影响因子：
3.2
通讯作者：
Wang, Lei
中科院分区：
文献类型：
--
作者：
Feng, Lu;Liu, Bin;Wang, Lei
先前在携带非fliC鞭毛蛋白特异性位点flk的大肠杆菌菌株中证明了单侧鞭毛相变化的发生。在这项研究中，我们研究了这一过程中涉及的机制。通过测序和序列分析，在所有描述的flk阳性的E.大肠杆菌菌株，包括本研究中鉴定的H35菌株（使用的其他菌株是H3，H36，H47和H53菌株），发现该区域除了flk鞭毛蛋白特异性基因flkA和fliC阻遏物基因flkB之外还含有推定的整合酶基因和侧翼直接重复序列，表明存在典型的基因组胰岛（GI），将其命名为flk GI。通过检测flk GI的切除的染色体外圆形形式来指示flk GI的水平转移潜力。通过产生H3和H47菌株的fliC表达变体，显示flk阳性菌株中的单侧鞭毛相变化由flk GI的切除介导。所提出的整合酶基因的功能通过缺失和互补试验来证实。确定了flk GI的潜在整合位点。flk阳性大肠杆菌鞭毛相变化的一般模型。大肠杆菌的表达形式为fliC（off）+flkA（on）→ fliC（on）+ flkA（none）。这是首次报道了E.杆菌
The occurrence of unilateral flagellar phase variation was previously demonstrated in Escherichia coli strains carrying the non-fliC flagellin-specifying locus flk. In this study, we investigated the mechanism involved in this process. By using sequencing and sequence analysis, the flk region between the chromosomal genes yhaC and rnpB was characterized in all described flk-positive E. coli strains, including the H35 strain identified in this study (the other strains used are H3, H36, H47, and H53 strains), and this region was found to contain a putative integrase gene and flanking direct repeats in addition to the flk flagellin-specifying gene flkA and a fliC repressor gene,flkB, indicating that there is a typical genomic islet (GI), which was designated the flk GI. The horizontal transfer potential of the flk GI was indicated by detection of the excised extrachromosomall circular form of the flk GI. By generating fliC-expressing variants of H3 and H47 strains, unilateral flagellar phase variation in flk-positive strains was shown to be mediated by excision of the flk GI. The function of the proposed integrase gene was confirmed by deletion and a complementation test. The potential integration sites of the flk GI were identified. A general model for flagellar phase variation in flk-positive E. coli strains can be expressed as fliC(off) + flk A(on) -> fliC(on) + flkA(none). This is the first time that a molecular mechanism for flagellar phase variation has been reported for E. coli.