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Conjugal transfer of a toxin-coding megaplasmid from Bacillus thuringiensis subsp. israelensis to mosquitocidal

Katherine Gammon1, Gareth W Jones, Steven J Hope

  • 1Cardiff School of Biosciences, Cardiff University, Museum Avenue, Cardiff CF10 3US, United Kingdom.

Applied and Environmental Microbiology
|March 7, 2006
PubMed

Insights

Transferring a mosquitocidal plasmid from Bacillus thuringiensis to Bacillus sphaericus enhanced mosquito control. The transconjugant bacteria showed increased toxicity and overcame resistance, though plasmid stability was moderate.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Insect Vector Control

Background:

  • Bacillus sphaericus and Bacillus thuringiensis subsp. israelensis are key bacterial agents for mosquito control.
  • Mosquitocidal toxins are produced during sporulation and encoded on the pBtoxis plasmid in B. thuringiensis.
  • Existing mosquito resistance to B. sphaericus necessitates novel control strategies.

Purpose of the Study:

  • To enhance mosquitocidal activity by transferring the pBtoxis plasmid from B. thuringiensis to B. sphaericus.
  • To assess the efficacy of the transconjugant against resistant mosquito populations.
  • To evaluate the stability of the transferred plasmid in the new host.

Main Methods:

  • Plasmid transfer using a bacterial mating technique.
  • Toxicity assays against Aedes aegypti larvae.
  • Evaluation of resistance breaking in Culex quinquefasciatus.
  • Assessment of plasmid stability during bacterial growth and sporulation.

Main Results:

  • Transconjugant B. sphaericus exhibited significantly higher toxicity to Aedes aegypti.
  • The transconjugant overcame resistance in Culex quinquefasciatus, attributed to Cry11A production.
  • Moderate plasmid stability was observed during vegetative growth, with significant loss during sporulation.

Conclusions:

  • Transferring the pBtoxis plasmid to B. sphaericus can enhance mosquitocidal efficacy and overcome resistance.
  • The Cry11A toxin appears crucial for overcoming B. sphaericus resistance.
  • Plasmid instability during sporulation presents a challenge for sustained application.

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