- 58 - Case 136-7117 Particularly effective B.t. insecticides are obtained by culturing to the sporulation stage novel transformant obtained on transforming B.t. kurstaki H.D. 562 with DNA expressing in the B.t. certain mutant endotoxin genes. Such transformants and other B.t. transformants generally may be obtained in high transformation frequencies by the electrotransformation of B.t. cells while in a hypertonic state followed by maintaining the cells in a hypertonic medium for a time sufficient to obtain intact cells. Transformation of B.t. tenebrionis and B.t. aizawai is also described.
