Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, Pennsylvania, United States of America.
PLoS One. 2022 Jul 14;17(7):e0268502. doi: 10.1371/journal.pone.0268502. eCollection 2022.
Research on the transfer of antibiotic resistance plasmids has been mainly focused on the large multi-drug resistance conjugative plasmids, while the transmission of small mobilizable plasmids remains under-investigated. A series of diverse ColE-like kanamycin resistance plasmids ("KanR plasmids") from Salmonella enterica were characterized previously. In this study, the 6.6-kb pSNC3-Kan from a Salmonella enterica serotype Newport isolate was investigated. It possessed highly conserved RNA I/II and Tn602 (IS903-aph-IS903) regions to two other KanR plasmids pSe-Kan and pSBardo-Kan, but carried a mobC-mobA/BD operon. The mobilization proteins encoded by the mob operon of pSNC3-Kan showed high sequence identity (~95%) to those of an E. coli plasmid pEC34B, except that MobE was not present; and were much less conserved to those of another KanR plasmid pSN11/00Kan (43% - 86% identity). Four structurally different KanR plasmids were investigated for their ability to be mobilized by the conjugal transfer (tra) genes from F and IncP plasmids. Transfer genes derived from IncP plasmids can efficiently mobilize KanR plasmids possessing the mob operons (mobC-mobA/BD), such as pSNC3-Kan and pSN11/00Kan, in bi-parental mating experiments. On the other hand, F tra genes were able to mobilize pU302S, pSNC3-Kan and pSe-Kan, but not pSN11/00Kan. A plasmid-borne mob operon was not required for mobilization of the oriT(F)-bearing pSe-Kan by the F tra genes. This study underscores the complexity of plasmid interaction and the importance of how small mobilizable plasmids may contribute to the spread of antibiotic resistance genes.
先前对来自沙门氏菌的一系列不同 ColE 样卡那霉素抗性质粒（“KanR 质粒”）进行了研究。在本研究中，对来自沙门氏菌纽波特血清型分离株的 6.6kb pSNC3-Kan 进行了研究。它具有高度保守的 RNA I/II 和 Tn602（IS903-aph-IS903）区域，可与另外两个 KanR 质粒 pSe-Kan 和 pSBardo-Kan 相互作用，但携带一个 mobC-mobA/BD 操纵子。pSNC3-Kan 的 mob 操纵子编码的移动蛋白与大肠杆菌质粒 pEC34B 的移动蛋白具有高度的序列同一性（~95%），但与另一个 KanR 质粒 pSN11/00Kan 的移动蛋白的同源性较低（43%-86%）。为了研究这些质粒能否通过 F 和 IncP 质粒的接合转移（tra）基因进行转移，对这四个结构不同的 KanR 质粒进行了研究。来自 IncP 质粒的转移基因可以有效地转移携带 mob 操纵子（mobC-mobA/BD）的 KanR 质粒，如 pSNC3-Kan 和 pSN11/00Kan，在双亲交配实验中。另一方面，F tra 基因能够转移 pU302S、pSNC3-Kan 和 pSe-Kan，但不能转移 pSN11/00Kan。F tra 基因转移 oriT（F）携带的 pSe-Kan 不需要质粒携带的 mob 操纵子。本研究强调了质粒相互作用的复杂性，以及小型可移动质粒如何有助于抗生素耐药基因传播的重要性。
