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Another Bacillus sphaericus serotype harbouring strains very toxic to mosquito larvae: serotype H6

H de Barjac1, I Thiery, V Cosmao-Dumanoir

  • 1WHO Collaborating Centre for Reference and Research on Entomopathogenic Bacillus, Lutte Biologique II, Institut Pasteur, Paris.

Annales De L'Institut Pasteur. Microbiology
|May 1, 1988
PubMed

Insights

Ten Ghanaian Bacillus sphaericus isolates, serotype H6, show high toxicity against mosquito larvae. These potent larvicidal strains are comparable to existing highly toxic Bacillus sphaericus strains.

Area of Science:

  • Microbiology
  • Entomology
  • Biochemistry

Background:

  • Bacillus sphaericus is a bacterium known for its larvicidal properties against mosquitoes.
  • Mosquito-borne diseases pose a significant global health threat, necessitating effective control strategies.
  • Identification and characterization of novel, highly toxic Bacillus sphaericus strains are crucial for vector control.

Purpose of the Study:

  • To identify and characterize Bacillus sphaericus isolates from Ghana for their larvicidal potential.
  • To determine the serotype and toxicity of these isolates against key mosquito species.
  • To investigate the protein composition of spore-crystal extracts from these potent strains.

Main Methods:

  • Isolation and culturing of Bacillus sphaericus from Ghanaian sources.
  • Larvicidal bioassays against Culex pipiens and Anopheles stephensi larvae.
  • Serotyping of Bacillus sphaericus isolates.
  • Analysis of spore-crystal extracts using SDS-PAGE and immunological methods.

Main Results:

  • Ten Bacillus sphaericus isolates from Ghana were identified as serotype H6.
  • These isolates exhibited high larvicidal toxicity against Culex pipiens and Anopheles stephensi.
  • The toxicity levels were comparable to well-established toxic strains like 1593, 2362 (serotype H5a,5b), and 2297 (serotype H25).
  • Spore-crystal extracts contained a 43-Kd polypeptide immunologically related to that of strain 2362.

Conclusions:

  • Ghanaian Bacillus sphaericus isolates of serotype H6 represent a promising source of potent larvicidal agents.
  • These findings expand the known diversity of highly toxic Bacillus sphaericus strains for mosquito control.
  • The identified 43-Kd polypeptide may play a role in the larvicidal activity of these strains.

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