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Jumbo phage-mediated transduction of genomic islands

Yansong Zhao1, Yue Ma2, Christina Vasileiou1

  • 1Department of Microbial Population Biology, Max Planck Institute for Evolutionary Biology, Plön 24306, Germany.

Proceedings of the National Academy of Sciences of the United States of America
|October 28, 2025
PubMed

Insights

Researchers discovered novel mobile genetic elements (MGEs) in Pseudomonas fluorescens, transferred by jumbo phages. These MGEs enhance bacterial fitness through phage defense systems, expanding our understanding of horizontal gene transfer.

Area of Science:

  • Microbiology
  • Genetics
  • Molecular Biology

Background:

  • Bacteria gain new genes through horizontal gene transfer (HGT), primarily via mobile genetic elements (MGEs).
  • While plasmids, phages, and integrative conjugative elements are known, the full diversity of MGEs is not well understood.

Purpose of the Study:

  • To investigate the diversity and characteristics of MGEs acquired by *Pseudomonas fluorescens*.
  • To explore the mechanisms of transfer and the functional implications of these novel MGEs.

Main Methods:

  • Culturing *Pseudomonas fluorescens* SBW25 with sterile filtrate from compost communities.
  • Genome sequencing of bacterial colonies to identify acquired mobile elements.
  • Bioinformatic analysis of DNA sequence databases to find similar elements and infer transfer patterns.
  • Detailed analysis of a specific element (I55) to determine its transfer mechanism and fitness effects.

Main Results:

  • Acquisition of three distinct MGEs by *P. fluorescens*, integrating downstream of *tmRNA* and encoding tyrosine integrase and phage defense genes.
  • These elements lack genes for autonomous transfer, suggesting alternative transfer mechanisms.
  • Similar elements are widespread in *Pseudomonas* and other genera, including *Vibrio*.
  • The I55 element is transferred by jumbo phages and provides a fitness advantage via a type II restriction-modification system.

Conclusions:

  • Identified novel MGEs in *Pseudomonas* that are transferred by jumbo phages.
  • These MGEs contribute to bacterial adaptation by conferring fitness benefits, such as phage resistance.
  • Highlights the significant, yet underappreciated, diversity of MGEs and their roles in bacterial evolution and HGT.
Keywords:
comparative genomicsexperimental evolutionjumbo bacteriophagesphage satellites

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