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While every living organism has a genome of some kind (be it RNA, or DNA), there is considerable variation in the sizes of these blueprints. One major factor that impacts genome size is whether the organism is prokaryotic or eukaryotic. In prokaryotes, the genome contains little to no non-coding sequence, such that genes are tightly clustered in groups or operons sequentially along the chromosome. Conversely, the genes in eukaryotes are punctuated by long stretches of non-coding sequence.
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Updated: Jun 12, 2025

Determination of the Optimal Chromosomal Locations for a DNA Element in Escherichia coli Using a Novel Transposon-mediated Approach
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Intragenic DNA inversions expand bacterial coding capacity.

Rachael B Chanin1, Patrick T West1, Jakob Wirbel1

  • 1Department of Medicine, Division of Hematology, Stanford University, Stanford, CA, USA.

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|September 25, 2024
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Summary
This summary is machine-generated.

Bacteria generate diversity using DNA inversions, a process called phase variation. Researchers discovered novel intragenic invertons within genes, expanding bacterial protein diversity without increasing genome size.

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Area of Science:

  • Microbiology
  • Genomics
  • Bioinformatics

Background:

  • Bacterial populations exhibit heterogeneity, not strict clonality, due to mechanisms like phase variation.
  • Phase variation, often mediated by DNA inversions, alters gene expression and impacts bacterial fitness and survival.
  • DNA inversions can flip promoter orientations, controlling gene transcription.

Purpose of the Study:

  • To develop a computational tool (PhaVa) for identifying DNA inversions in long-read sequencing data.
  • To discover and characterize a novel class of DNA inversions, termed 'intragenic invertons', located within genes.

Main Methods:

  • Development of the PhaVa computational tool for DNA inversion detection.
  • Analysis of long-read sequencing datasets from bacterial and archaeal isolates.
  • Experimental validation of identified intragenic invertons in *Bacteroides thetaiotaomicron*.

Main Results:

  • Identification of 372 novel intragenic invertons across diverse bacterial and archaeal genomes.
  • Demonstration that intragenic invertons enable genes to encode multiple protein variants by flipping internal DNA sequences.
  • Experimental validation of ten intragenic invertons and characterization of one in the *thiC* gene.

Conclusions:

  • Intragenic invertons represent a significant discovery, expanding the coding capacity of bacterial genomes.
  • PhaVa is a valuable tool for identifying DNA inversions, facilitating further research into bacterial genome dynamics.
  • This mechanism provides bacteria with a novel strategy for generating protein diversity and adapting to environmental changes.