Discovery and functional characterization of a novel PilV variant in a mcr-1-positive IncI2 plasmid
4 affiliations
- 1State Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
- 2College of Veterinary Medicine, China Agricultural University, Beijing, China
- 3Sanya Institute, China Agricultural University, Sanya, China
- 4The Second Affiliated Hospital Zhejiang University School of Medicine, Hangzhou, China
Abstract
IncI2-type plasmids are major vehicles for the dissemination of mcr-1. These plasmids encode a type IV secretion system (T4SS) that mediates conjugative transfer and a type IV pilus (T4P) that facilitates mating-pair formation. Shufflon-mediated diversity of tip adhesin PilV of T4P may contribute to the extensive dissemination of IncI2 plasmids. Herein, we identified a novel shufflon segment forming an active new PilV variant from an IncI2 plasmid, which was named PilV-E and was detected in 127 of 501 (25.35%) complete IncI2 plasmids in public databases. We further demonstrated that strains harboring the single PilV-E variant displayed a distinct functional profile, characterized by both robust biofilm formation and high Caco-2 adhesion. Compared with the ΔpilV-shufflon-rci strain, the PilV-E-carrying strain showed increased biofilm formation (OD590 from 1.50 to 2.60), increased Caco-2 adhesion (0.04% to 5.46%), and increased surface motility (1.20 to 1.87 cm/day). Among all variants, PilV-A' showed the strongest cell adhesion (6.00%), whereas PilV-B' showed the greatest motility (2.54 cm/day). Notably, PilV-E significantly restored conjugation frequency compared with the ΔpilV-shufflon-rci strain and displayed the highest and lowest frequencies when recipients were Escherichia coli (5.23 × 10−3) and Acinetobacter baumannii (4.46 × 10−8), respectively. All findings confirm that PilV-E serves as a novel and key tip adhesin of T4P and plays a crucial role in plasmid conjugation, indicating that the diversity of shufflon-mediated PilV variants has been underestimated and providing insight into the molecular basis for the extensive spread of IncI2 plasmids.
IMPORTANCE: The plasmid-mediated colistin resistance gene mcr-1 has become a major public health concern because it compromises one of the last-line treatments for multidrug-resistant Gram-negative bacterial infections. IncI2 plasmids are among the most important vehicles for the dissemination of mcr-1, but the molecular factors that facilitate their efficient transfer remain insufficiently understood. In this study, we identified PilV-E, a novel shufflon-associated type IV pilus tip adhesin encoded by a human-derived IncI2 plasmid, and demonstrated its contribution to bacterial fitness-related phenotypes and conjugative transfer. The prevalence of PilV-E among complete IncI2 plasmids further indicates that this variant has been overlooked in previous studies. These findings expand our understanding of shufflon-mediated PilV diversity and provide new insight into how IncI2 plasmids participate in the efficient dissemination of mcr-1 among diverse bacterial species, including clinically important pathogens.
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BibTeX
@article{an2026discovery,
title = {{Discovery and functional characterization of a novel PilV variant in a mcr-1-positive IncI2 plasmid}},
author = {Chen An and Jie Yang and Silin Liu and Dongyan Shao and Hongwei Zhou and Yuchen Wu and Yang Wang and Rong Zhang and Jianzhong Shen and Congming Wu and Yingbo Shen},
journal = {Microbiology Spectrum},
year = {2026},
month = sep,
doi = {10.1128/spectrum.01825-26},
url = {https://doi.org/10.1128/spectrum.01825-26},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Discovery and functional characterization of a novel PilV variant in a mcr-1-positive IncI2 plasmid
AU - Chen An
AU - Jie Yang
AU - Silin Liu
AU - Dongyan Shao
AU - Hongwei Zhou
AU - Yuchen Wu
AU - Yang Wang
AU - Rong Zhang
AU - Jianzhong Shen
AU - Congming Wu
AU - Yingbo Shen
PY - 2026
DA - 2026/09/30
JO - Microbiology Spectrum
DO - 10.1128/spectrum.01825-26
UR - https://doi.org/10.1128/spectrum.01825-26
AB - IncI2-type plasmids are major vehicles for the dissemination of mcr-1. These plasmids encode a type IV secretion system (T4SS) that mediates conjugative transfer and a type IV pilus (T4P) that facilitates mating-pair formation. Shufflon-mediated diversity of tip adhesin PilV of T4P may contribute to the extensive dissemination of IncI2 plasmids. Herein, we identified a novel shufflon segment forming an active new PilV variant from an IncI2 plasmid, which was named PilV-E and was detected in 127 of 501 (25.35%) complete IncI2 plasmids in public databases. We further demonstrated that strains harboring the single PilV-E variant displayed a distinct functional profile, characterized by both robust biofilm formation and high Caco-2 adhesion. Compared with the ΔpilV-shufflon-rci strain, the PilV-E-carrying strain showed increased biofilm formation (OD590 from 1.50 to 2.60), increased Caco-2 adhesion (0.04% to 5.46%), and increased surface motility (1.20 to 1.87 cm/day). Among all variants, PilV-A' showed the strongest cell adhesion (6.00%), whereas PilV-B' showed the greatest motility (2.54 cm/day). Notably, PilV-E significantly restored conjugation frequency compared with the ΔpilV-shufflon-rci strain and displayed the highest and lowest frequencies when recipients were Escherichia coli (5.23 × 10−3) and Acinetobacter baumannii (4.46 × 10−8), respectively. All findings confirm that PilV-E serves as a novel and key tip adhesin of T4P and plays a crucial role in plasmid conjugation, indicating that the diversity of shufflon-mediated PilV variants has been underestimated and providing insight into the molecular basis for the extensive spread of IncI2 plasmids. IMPORTANCE: The plasmid-mediated colistin resistance gene mcr-1 has become a major public health concern because it compromises one of the last-line treatments for multidrug-resistant Gram-negative bacterial infections. IncI2 plasmids are among the most important vehicles for the dissemination of mcr-1, but the molecular factors that facilitate their efficient transfer remain insufficiently understood. In this study, we identified PilV-E, a novel shufflon-associated type IV pilus tip adhesin encoded by a human-derived IncI2 plasmid, and demonstrated its contribution to bacterial fitness-related phenotypes and conjugative transfer. The prevalence of PilV-E among complete IncI2 plasmids further indicates that this variant has been overlooked in previous studies. These findings expand our understanding of shufflon-mediated PilV diversity and provide new insight into how IncI2 plasmids participate in the efficient dissemination of mcr-1 among diverse bacterial species, including clinically important pathogens.
SN - 2165-0497
ER -