[Source: PLoS One, full page: (LINK). Abstract, edited.]
OPEN ACCESS / PEER-REVIEWED / RESEARCH ARTICLE
Fitness cost of a mcr-1-carrying IncHI2 plasmid
Ke Ma, Yu Feng, Zhiyong Zong
Published: December 26, 2018 / DOI: https://doi.org/10.1371/journal.pone.0209706
IncHI2 is a common type of large mcr-1-carrying plasmids that have been found worldwide. Large plasmids could impose metabolic burden for host bacterial strains, we therefore examine the stability and fitness cost of a mcr-1-carrying 265.5-kb IncHI2 plasmid, pMCR1_1943, in Escherichia coli in nutrient-rich LB and nutrient-restricted M9 broth. Stability tests revealed that pMCR1_1943 was stably maintained with a stability frequency of 0.99±0.01 (mean ± standard deviation) after 880 generations in LB and 0.97±0.00 after 220 generations in M9 broth. Relative fitness (expressed as w, defined as relative fitness of the plasmid-carrying strain compared to the plasmid-free progenitor strain) was examined using the 24-h head to head competitions. pMCR1_1943 initially imposed costs (w, 0.88±0.03 in LB, 0.87±0.01 in M9) but such costs were largely reduced after 14-day cultures (w, 0.97±0.03 in LB, 0.95±0.03 in M9). The stable maintenance and the largely compensated cost after passage may contribute to the wide spread of mcr-1-carrying IncHI2 plasmids. To investigate potential mechanisms for the reduced fitness cost, we performed whole genome sequencing and single nucleotide polymorphism calling for the competitor strains. We identified that molecular chaperone-encoding dnaK, cell division protein-encoding cpoB and repeat protein-encoding rhsC were associated with the cost reduction for pMCR1_1943, which may represent new mechanisms for host bacterial strains to compensate fitness costs imposed by large plasmids and warrant further studies.
Citation: Ma K, Feng Y, Zong Z (2018) Fitness cost of a mcr-1-carrying IncHI2 plasmid. PLoS ONE 13(12): e0209706. https://doi.org/10.1371/journal.pone.0209706
Editor: Günther Koraimann, University of Graz, AUSTRIA
Received: September 20, 2018; Accepted: December 10, 2018; Published: December 26, 2018
Copyright: © 2018 Ma et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: Short reads of genome sequences of the strains in the present study have been deposited into Sequence Read Archive of GenBank under the accession no. SRR7031288, SRR7031297, SRR7031306, SRR7031313, SRR7031315, SRR7031316, SRR7031320, SRR7031295.
Funding: ZZ was supported by grants from the National Natural Science Foundation of China (project no. 81772233 and 81661130159) and the Newton Advanced Fellowship, Royal Society, UK (NA150363). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Keywords: Antibiotics; Drugs Resistance; Colistin; MCR1.