Abstract
Four strains of Bacillus thuringiensis subsp. darmstadiensis (serotype H 10) were compared by scanning electron microscopy for morphological differences in parasporal crystal architecture, for differences in toxicity spectra, and by agarose gel electrophoresis of cell lysates for plasmid DNA content. While all of the strains harbored a common large plasmid (107.15 megadaltons, Mdal) other differences in crystal morphology, toxicity and plasmid array were in most cases distinctive. Strains 73-E-10-2 and 73-E-10-16 produced spheroidal-shaped crystals, were toxic to dipteran but not lepidopteran larvae, and harbored four similar plasmids of the following approximate molecular weights : 3.30, 8.95, 9.47 and 107.15 Mdal. The reference strain produced rhomboidal-shaped crystals, were toxic to lepidopteran but not dipteran larvae, and contained only one plasmid with a mass of 107.15 Mdal. Strain 74-E-37-14 produced diamond-shaped crystals with concaved surface, were not toxic to dipteran or lepidopteran larvae and harbored two plasmids with approximate masses of 7.78 and 107.15 Mdal. The importance of these strains to genetic studies on crystal inclusion production is discussed.
