Date of Award


Degree Type


Degree Name

Doctor of Philosophy


The parasporal inclusions of B. thuringiensis subspecies kurstaki, subspecies israelensis, subspecies schwetzova, subspecies alesti, subspecies finitinus, and B. cereus subspecies medusa and subspecies lewinia were purified and analyzed by one-dimensional slab gel electrophoresis. The inclusion of each of the above subspecies was composed of different polypeptides. The protein composition of the inclusions was correlated with the sahpe, structure and toxicity of the inclusion. Four types of inclusions were formed by the seven subspecies studied. Three representative subspecies were chosen for further study.;Two strains of B. cereus and eight subspecies of B. thuringiensis were screened for the presence of plasmid DNA. B. cereus T contained two large plasmids, (17 Md. and 14 Md.), whereas the other strain, B. cereus N, contained no plasmid DNA. All B. thuringiensis subspecies contained plasmid DNA ranging from about 50 Md. to 1.3 Md. A non-crystal forming variant of B. thuringiensis subspecies kurstaki contained no plasmid NDA. B. thuringiensis subspecies schwetzova, subspecies M-13 and subspecies B-30-1 contained identical plasmid profiles. The plasmid profiles of B. thuringiensis subspecies sotto and B. thuringinesis subspecies alesti were markedly different than those of the other subspecies. B. cereus subspecies medusa contained three plasmids, (3.1, 6.4 and 21.6 Md.). Endonuclease restriction mapping indicated that the 6.4 and 12.6 Md. plasmids were unique and were not multimers of the 3.1 Md. plasmid. Loss of the plasmid and hence the loss of the inclusion in B. cereus subspecies medusa and B. thuringiensis subspecies kurstaki was achieved by growth of the bacterium at 42(DEGREES)C. Acridine orange and ethidium bromide, known plasmid curing agents, did not result in the loss of the inclusion. When grown at 42(DEGREES)C, B. cereus subspecies medusa formed a small core crystal, whereas B. thuringiensis subspecies kurstaki lost the whole inclusion. This curing phenomenon also occurred spontaneously and as a result of repeated subculturing of the L07 strain on sheep blood agar. These core crystal variants had lost the 12.6 Md. plasmid. Another variant of B. cereus subspecies medusa, L013, which was isolated on sheep blood agar, formed cells that were smaller than the wild type cells. The L013 variant was sensitive to penicillin and ampicillin whereas the wild type was resistant. The L013 variant contained a 7.2 Md. plasmid which was not present in the wild type. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UMI



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