Insecticidal activity
Fecal isolates of B. thuringiensis were analyzed in terms of the oral toxicity of the resulting sporulated bacterial cultures against insect larvae to identify the properties of the obtained serotypes. Of the 190 isolates tested, 133 (70.1%) showed insecticidal activity, 128 killed B. mori and Aedes sp. larvae, 3 isolates were monotoxic to B. mori, and 2 more were capable to destroy onlyAedes sp., proving their biological selectivity against laboratory test objects. The results are detailed in Table 2.
[Table 2 here]
All H3abc samples obtained with bipyramid inclusions were toxic to both insect species, i.e., to both B. mori and Aedesmosquitoes. The obtained H5ab/21 isolates exhibited double toxicity. Monotoxic B. thuringiensis against Aedes sp. were found only among organisms forming spherical parasporal inclusions. Examples included an H4ab/43 serotype isolate.
The insecticidal activity of the bacterial serotypes is an integral biochemical component when characterizing different serotypes. The studies carried out mainly with recently characterized serotypes allow the hypothesis that biochemical traits, although important, cannot be used for analysis within or between serotypes. This method, combined with H serotyping, may be effective when certain traits remain unclear. In addition, there are suggestions as to how reliable the microscopy methods are. These methods have proven effective for many bacteria, in addition, their results are comparable with those obtained by traditional methods. In this regard, in some cases, it is possible to use not only traditional methods but also microscopic methods.