1. Successful spread of mcr-1-bearing IncX4 plasmids is associated with variant in replication protein of IncX4 plasmids
- Author
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Lingxian Yi, Kaiyang Yu, Guolong Gao, Rongmin Zhang, Luchao Lv, Daojin Yu, Jun Yang, and Jian-Hua Liu
- Subjects
IncX4 plasmids ,mcr-1 ,Fitness burden ,Antibiotic resistance ,Microbiology ,QR1-502 - Abstract
ABSTRACT: IncX4 plasmids are one of the most epidemiologically successful vehicles for mcr-1 spread. Here we found that the IncX4 plasmids carried two different replication proteins encoded by genes pir-1 and pir-2, respectively, but mcr-1 was only carried by IncX4 plasmid encoding pir-1. The copy number of pir-2 encoding plasmids (3.15 ± 0.9 copies) are higher than that of pir-1 encoding plasmids (0.85 ± 0.5 copies). When mcr-1 was cloned into IncX4 plasmid encoding pir-2, the higher copy number of these plasmids resulted in increased expression of mcr-1 and a greater fitness burden on their host cells. However, these plasmids exhibited a lower rate of invasion into the bacterial population compared with mcr-1-positive plasmids encoding the pir-1 gene. These findings collectively explain the absence of mcr-1 in all IncX4 plasmids encoding pir-2. Our results further confirmed that low-copy numbers are important for the spread of mcr-1 plasmid from the perspective of natural evolution.
- Published
- 2024
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