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Ubiquitous Conjugative Mega-Plasmids of Acinetobacter Species and Their Role in Horizontal Transfer of Multi-Drug

Sofia Mindlin1, Olga Maslova1, Alexey Beletsky2

  • 1Institute of Molecular Genetics of National Research Center "Kurchatov Institute", Moscow, Russia.

Frontiers in Microbiology
|October 8, 2021
PubMed

Insights

Conjugative mega-plasmids in Acinetobacter species facilitate adaptation and spread of resistance genes. Environmental strains show heavy metal resistance, while clinical strains accumulate antibiotic resistance via transposons and integrons.

Area of Science:

  • Microbiology
  • Genetics
  • Evolutionary Biology

Background:

  • Conjugative mega-plasmids are crucial for bacterial adaptation, carrying numerous accessory genes that enable survival in new environments.
  • These plasmids facilitate their own spread and the mobilization of smaller plasmids through conjugation.
  • Acinetobacter species are significant opportunistic pathogens, and understanding their resistance mechanisms is critical.

Purpose of the Study:

  • To characterize a newly discovered family of multi-drug resistance mega-plasmids (group III-4a) in Acinetobacter species.
  • To investigate the structural features, replication mechanisms, and transfer capabilities of these mega-plasmids.
  • To explore the correlation between the living conditions of Acinetobacter strains and the genetic makeup of their mega-plasmids.

Main Methods:

  • Detailed characterization of mega-plasmid structure, including identification of the replication (rep) gene and origin of replication.
  • Analysis of plasmid mobility within and between Acinetobacter species.
  • Mobilization assays for small plasmids with different mobilization (mob) genes.
  • Comparative analysis of mega-plasmids from environmental and clinical Acinetobacter isolates.

Main Results:

  • The study details the plasmid backbone structure and identifies key replication genes for group III-4a mega-plasmids.
  • These mega-plasmids exhibit inter-species mobility within Acinetobacter and can mobilize small plasmids.
  • A significant prevalence of mega-plasmids was observed in natural Acinetobacter populations.
  • Clinical strains showed a reduction in heavy metal resistance genes, with a concurrent increase in antibiotic resistance genes acquired via transposons and integrons, unlike environmental strains.

Conclusions:

  • Group III-4a mega-plasmids are key players in the adaptation and evolution of Acinetobacter species.
  • These mega-plasmids significantly contribute to the dissemination of multi-drug resistance within Acinetobacter populations.
  • The observed differences in mega-plasmid content between environmental and clinical strains highlight the role of selective pressures in shaping bacterial resistance.
Keywords:
accessory regioniteronsmobilizationphylogenetic analysisplasmid backbonereplication initiation proteintra-operon

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