[Scanning tunneling and electron microscopy of parasporal crystals in Bacillus thuringiensis]

Comparison of the forms of parasporal inclusions in Bacillus thuringiensis subsp. kurstaki and B. thuringiensis subsp. tenebrionis under a scanning electron microscope showed that, in addition to bipyramidal and cuboid crystals, cells of the subspecies kurstaki are able to form crystals taking the shape of flat parallelopipeds typical of the subspecies tenebrionis. The inclusions in the subspecies tenebrionis vary in size and electron density. Examination of the structure of crystals in B. thuringiensis subsp. tenebrionis under a scanning tunneling microscope showed that delta-endotoxins in the crystals are assembled in globules 5.0 nm in diameter and 1.0 nm in height. The globules are connected by its bases and form chains. The subunits of tetragonal crystals in the subspecies tenebrionis are vertically oriented with respect to the chain axis, as was revealed by other methods for subunits of bipyramidal crystals of the subspecies kurstaki.