Serotype H5a5b is a major clone within mosquito-pathogenic strains of Bacillus sphaericus

Seventy six mosquito pathogenic strains of Bacillus sphaericus and 10 non-pathogens were examined by pulsed field gel electrophoresis (PFGE) of SmaI-digested chromosomal DNA. Non-pathogenic strains were clearly distinguished from the entomopathogenic types which were assigned to 21 groups (SmaI restriction patterns; SRPs). Some agreement between SRP based on PFGE and serotyping was noted, in particular all 39 strains of serotype 5a5b examined revealed identical SRPs indicating total conservation of the SmaI restriction site in these bacteria. Serotype 5a5b (SRP 12) strains comprise a widely distributed and abundant clonal lineage. Most serotypes, however, were divided into several SRPs. Seven strains from serotype 2a2b were recovered in five SRPs in which toxin synthesis was correlated with chromosomal structure. Similarly, toxicity correlated with SRP in strains from serotypes 3 and 6.