Primary powders of Bacillus sphaericus strain S2
isolated from soil samples in Brazil, and strain 2362 were
produced in a 14 liter fermentor. Growth patterns and
sporulation observed in three trials with strains S2 and 2362
in the fermentor were similar. Second-instar larvae of
Culex quinquefasciatus, Anopheles albimanus, Anopheles
quadrimaculatus, and Aedes aegypti exposed for 48 hr
to strain S2 responded with LC50 values of 0.25, 5.95, 12.28
and 140.0 ppb of lyophilized primary powder, respectively.
Under the same conditions, strain 2362 resulted in LC50 values
of 0.39, 7.16, 16.93 and 307.0 ppb of lyophilized primary
powder, respectively, in those mosquito larvae. Statistical
analysis of the bioassay data did not show significant
differences among LC50 values observed in B. sphaericus
strains S2 and 2362, at the 0.05 level.
Toxins of strains S2 and 2362 were extracted at pH 12
with NaOH. Electrophoresis of the extracts in polyacrylamide
gel under denaturing conditions revealed the 51 and 42 kDa
toxins in both S2 and 2362 B. sphaericus strains. The
presence of the 42 kDa peptide in the extracts was confirmed
by Western blot and Elisa, with anti-42 kDa IgG previously
prepared from strain 2362.