Lateral gene transfer in vitro in the intracellular pathogen Chlamydia trachomatis
Lateral gene transfer in vitro in the intracellular pathogen Chlamydia trachomatis
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DOI：
10.1128/jb.00845-06
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发表时间：
2007-02-01
影响因子：
3.2
通讯作者：
Potucek, Yvonne
中科院分区：
文献类型：
--
作者：
DeMars, Robert;Weinfurter, Jason;Potucek, Yvonne
在性传播疾病沙眼衣原体分离株中发现了由横向基因转移（LGT）产生的基因重组，但尚未描述LGT在沙眼衣原体中的机制。我们在这里描述了一个系统，很容易检测沙眼衣原体LGT体外，这可能有助于发现其机制。在没有抗生素的情况下，宿主细胞同时感染了一种耐奥菲沙星突变体和另一种耐林可霉素、甲氧苄啶或利福平突变体。选择双耐药沙眼衣原体分离物的后代检测到明显的重组频率为10（-4）至10(-3)，与单亲对照感染的后代中双耐药自发突变的频率相似，为10(4)倍。在没有抗生素的情况下，从它们分离出的多克隆双耐药群体和克隆具有亲本突变体中存在的特异性耐药突变；缺乏相应的正常核苷酸表明它们已被同源重组所取代。这些结果消除了自发突变、菌株间互补和异型抗性，这些都是我们实验中起源于混合感染的多重耐药沙眼原体的一般解释，并证明了重组体的遗传稳定性。我们观察到的这种LGT可能有助于通过产生新的等位基因或多态性位点的等位基因组合来创建新的菌株进行功能研究，也可能在体内传播抗生素抗性基因。沙眼衣原体中明显没有噬菌体和结合质粒，这表明LGT可能是通过自然DNA转化发生的。因此，该实验系统可能对通过DNA转移来改变沙眼衣原体的基因有影响。
Genetic recombinants that resulted from lateral gene transfer (LGT) have been detected in sexually transmitted disease isolates of Chlamydia trachomatis, but a mechanism for LGT in C. trachomatis has not been described. We describe here a system that readily detects C. trachomatis LGT in vitro and that may facilitate discovery of its mechanisms. Host cells were simultaneously infected in the absence of antibiotics with an ofiloxacin-resistant mutant and a second mutant that was resistant to lincomycin, trimethoprim, or rifampin. Selection for doubly resistant C. trachomatis isolates in the progeny detected apparent recombinant frequencies of 10(-4) to 10(-3), similar to 10(4) times more frequent than doubly resistant spontaneous mutants in progeny from uniparental control infections. Polyclonal doubly resistant populations and clones isolated from them in the absence of antibiotics had the specific resistance-conferring mutations present in the parental mutants; absence of the corresponding normal nucleotides indicated that they had been replaced by homologous recombination. These results eliminate spontaneous mutation, between-strain complementation, and heterotypic resistance as general explanations of multiply resistant C trachomatis that originated in mixed infections in our experiments and demonstrate genetic stability of the recombinants. The kind of LGT we observed might be useful for creating new strains for functional studies by creating new alleles or combinations of alleles of polymorphic loci and might also disseminate antibiotic resistance genes in vivo. The apparent absence of phages and conjugative plasmids in C. trachomatis suggests that the LGT may have occurred by means of natural DNA transformation. Therefore, the experimental system may have implications for genetically altering C. trachomatis by means of DNA transfer.