Bacillus sphaericus

Definition

A Gram-positive, spore-forming soil bacterium, now classified as Lysinibacillus sphaericus, notable in entomology for the larvicidal activity of certain strains against mosquito larvae. The binary toxin produced by pathogenic strains binds specifically to midgut receptors in Culex and Anopheles larvae, causing lysis of gut epithelial cells. Historically used as a biological control agent, particularly where Bacillus thuringiensis israelensis resistance has developed or for targeting Culex populations in polluted waters where Bti efficacy is reduced.

Etymology

Example

Formulations of Bacillus sphaericus are applied to stagnant water bodies to suppress Culex quinquefasciatus, a vector of West Nile virus and lymphatic filariasis, with residual activity lasting weeks longer than Bti treatments.

Synonyms

• Lysinibacillus sphaericus

Related Terms

• Bacillus thuringiensis
• Biological control
• mosquito
• Larvicide
• binary toxin
• Culex
• Anopheles
• vector control
• endospore

Usage Notes

The name Bacillus sphaericus reflects older nomenclature; current taxonomy places this species in Lysinibacillus. Not all strains are insecticidal—pathogenicity correlates with binary toxin gene presence. Strain efficacy varies by mosquito species: highly toxic to Culex and Anopheles, generally ineffective against Aedes aegypti in vegetative states though some activity is reported. Resistance has been documented in field populations after repeated applications.