Liu Yang, Gao Yanan, Liu Xiaohong, Liu Qin, Zhang Yuanxing, Wang Qiyao, Xiao Jingfan
State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China.
Shanghai Engineering Research Center of Maricultured Animal Vaccines, Shanghai, China.
BMC Microbiol. 2017 May 12;17(1):112. doi: 10.1186/s12866-017-1013-7.
Conjugation is a major type of horizontal transmission of genes that involves transfer of a plasmid into a recipient using specific conjugation machinery, which results in an extended spectrum of bacterial antibiotics resistance. However, there is inadequate knowledge about the regulator and mechanisms that control the conjugation processes, especially in an aquaculture environment where a cocktail of antibiotics may be present. Here, we investigated these with pEIB202, a typical multi-drug resistant IncP plasmid encoding tetracycline, streptomycin, sulfonamide and chloramphenicol resistance in fish pathogen Edwardsiella piscicida strain EIB202.
We used transposon insertion sequencing (TIS) to identify genes that are responsible for conjugation transfer of pEIB202. All ten of the plasmid-borne type IV secretion system (T4SS) genes and a putative lipoprotein p007 were identified to play an important role in pEIB202 horizontal transfer. Antibiotics appear to modulate conjugation frequencies by repressing T4SS gene expression. In addition, we identified topA gene, which encodes topoisomerase I, as an inhibitor of pEIB202 transfer. Furthermore, the RNA-seq analysis of the response regulator EsrB encoded on the chromosome also revealed its essential role in facilitating the conjugation by upregulating the T4SS genes.
Collectively, our screens unraveled the genetic basis of the conjugation transfer of pEIB202 and the influence of horizontally acquired EsrB on this process. Our results will improve the understanding of the mechanism of plasmid conjugation processes that facilitate dissemination of antibiotic resistance especially in aquaculture industries.
接合是基因水平转移的一种主要类型，它涉及使用特定的接合机制将质粒转移到受体中，这会导致细菌抗生素耐药谱的扩大。然而，对于控制接合过程的调节因子和机制，我们了解不足，尤其是在可能存在抗生素混合物的水产养殖环境中。在此，我们使用鱼类病原菌杀鲑气单胞菌EIB202中的典型多药耐药IncP质粒pEIB202来研究这些问题，该质粒编码对四环素、链霉素、磺胺类药物和氯霉素的耐药性。
我们使用转座子插入测序（TIS）来鉴定负责pEIB202接合转移的基因。所有十个质粒携带的IV型分泌系统（T4SS）基因和一个假定的脂蛋白p007被确定在pEIB202水平转移中起重要作用。抗生素似乎通过抑制T4SS基因表达来调节接合频率。此外，我们鉴定出编码拓扑异构酶I的topA基因是pEIB202转移的抑制剂。此外，对染色体上编码的应答调节因子EsrB的RNA测序分析也揭示了其通过上调T4SS基因促进接合的重要作用。
总体而言，我们的筛选揭示了pEIB202接合转移的遗传基础以及水平获得的EsrB在此过程中的影响。我们的结果将增进对促进抗生素耐药性传播的质粒接合过程机制的理解，尤其是在水产养殖行业。
