Diversity of Bacillus thuringiensis environmental isolates showing larvicidal activity specific for mosquitoes.

Abstract

Seven mosquito-specific strains of Bacillus thuringiensis isolated in Japan were examined for their flagellar (H) antigenicities and the properties of parasporal inclusion proteins. They were assigned to six H serovars: serovar fukuokaensis (H 3ade); serovar canadensis (H 5ac); serovar darmstadiensis (H 10); serovar kyushuensis (H 11ac); serovar shandongiensis (H 22); and an undescribed serovar belonging to H serotype 20. Purified parasporal inclusions exhibited moderate mosquito larvicidal activities with LC50 values ranging from 1 microgram ml-1 to 10 micrograms ml-1. The inclusions of these strains consisted of highly heterogeneous multiple protein components, and five distinct patterns were evident in their SDS-PAGE profiles. Antibodies against kyushuensis inclusion proteins were reactive with all strains to varying degrees, while israelensis antibodies gave only relatively weak reactions with the seven strains. Similarity in antibody-binding profiles was associated with similarity in SDS-PAGE profiles. In a given strain, different antisera gave altered immunoblot profiles. Haemolytic activity was shown by solubilized parasporal inclusion proteins of five of the seven strains.