Virulence Plasmids of Spore-Forming Bacteria

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Vicki Adams1, Jihong Li2, Jessica A Wisniewski1

  • 1Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Department of Microbiology, Monash University, Clayton, Vic 3800, Australia.

Microbiology Spectrum
|June 25, 2015
PubMed

Insights

Spore-forming bacteria like Clostridium and Bacillus use plasmid-encoded toxins for virulence. Understanding how these bacteria maintain toxin-encoding plasmids is crucial for disease control.

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Molecular Biology

Background:

  • Spore-forming bacteria, including Clostridium and Bacillus species, utilize plasmid-encoded virulence factors, primarily protein toxins, for pathogenesis.
  • Clostridium perfringens produces various toxins (e.g., enterotoxin, epsilon-toxin, beta-toxin, NetB) involved in histotoxic and enterotoxin diseases.
  • Toxin genes are typically located on large conjugative plasmids with conserved replication, maintenance, and conjugation regions.

Purpose of the Study:

  • To investigate the role of plasmid-encoded virulence factors in spore-forming bacteria.
  • To explore the mechanisms of plasmid maintenance in Clostridium perfringens, particularly the stable maintenance of multiple toxin plasmids.
  • To examine the genetic basis of toxin production in other medically relevant bacteria like Clostridium tetani, Clostridium botulinum, and Bacillus anthracis.

Main Methods:

  • Genetic studies to determine the role of toxins in disease.
  • Analysis of plasmid replication, maintenance, and conjugation regions.
  • Comparative genomics of toxin-encoding plasmids across different bacterial species.

Main Results:

  • Plasmid-encoded protein toxins are common virulence factors in Clostridium and Bacillus species.
  • Genes for toxins like C. perfringens enterotoxin, epsilon-toxin, beta-toxin, and NetB are plasmid-borne.
  • While conjugation loci are understood, plasmid maintenance mechanisms, especially for multiple plasmids in C. perfringens, require further investigation.
  • Toxin gene location varies in neurotoxic clostridia; Bacillus anthracis virulence is plasmid-determined (pXO1 for toxins, pXO2 for capsule).

Conclusions:

  • Plasmid-encoded toxins are central to the virulence of many spore-forming bacteria.
  • Understanding plasmid maintenance is key to explaining the stable co-existence of multiple virulence plasmids in pathogens like C. perfringens.
  • Plasmid and chromosomal elements contribute to virulence across diverse spore-forming genera.

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