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Two Bacillus sphaericus binary toxins share the midgut receptor binding site: implications for resistance of Culex

Maria Helena Neves Lobo Silva-Filha1, Cláudia Maria Fontes de Oliveira, Lêda Regis

  • 1Departamento de Entomologia, Centro de Pesquisas Aggeu Magalhães-FIOCRUZ, Av. Moraes Rêgo s/n, Recife-PE 50670-420, Brazil. mhneves@cpqam.fiocruz.br

FEMS Microbiology Letters
|December 16, 2004
PubMed

Insights

Bacillus sphaericus toxins Bin1 and Bin2 share a binding site in mosquito midgut membranes. Resistance to these toxins in Culex pipiens larvae involves the loss of these specific binding receptors.

Area of Science:

  • Molecular biology
  • Entomology
  • Biochemistry

Background:

  • Bacillus sphaericus produces binary toxins (Bin1 and Bin2) highly effective against mosquito larvae.
  • These toxins target specific receptors in the larval midgut brush border membranes (BBMF).
  • Understanding toxin-receptor interactions is crucial for developing effective mosquito control strategies.

Purpose of the Study:

  • To investigate the binding sites of Bin1 and Bin2 toxins from Bacillus sphaericus in Culex pipiens larvae.
  • To elucidate the molecular mechanisms underlying resistance to these toxins in mosquito populations.

Main Methods:

  • Comparative analysis of toxin binding to BBMF from susceptible and resistant mosquito colonies.
  • Selection of mosquito colonies for resistance to specific Bacillus sphaericus strains.
  • Assessment of receptor presence and binding affinity using biochemical assays.

Main Results:

  • Bin1 and Bin2 toxins share a common binding site on Culex pipiens larval BBMF.
  • A mosquito colony highly resistant to Bin2 toxin showed a complete loss of Bin2 receptors in its BBMF.
  • Bin1 toxin failed to bind to BBMF from a Bin2-resistant colony, indicating receptor specificity.

Conclusions:

  • The loss of functional BBMF-bound receptors is a primary mechanism for mosquito resistance to Bacillus sphaericus binary toxins.
  • This finding has significant implications for managing insecticide resistance and developing new vector control agents.

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