Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Phage-med-1, a phage-like-particle (approx. 22 nm in diameter) specifically found in stage II sporulating cells of B. medusa and initially reported as RNA containing was studied further. Similar particles, designated as (SLASHCIRC)isr-1, (SLASHCIRC)kyu-1 and (SLASHCIRC)10-2-1, were subsequently found in Bacillus thuringiensis subsp. israelensis (serotype 14), B. thuringiensis subsp. kyushuensis (serotype 11) and B. thuringiensis isolate 73-E-10-2 (serotype 10). These strains share the unique character of producing solely ovoid or round parasporal crystalline inclusion (cry) toxic to mosquito larvae.;An improved purification enabled the phage-like-particles (PLP) close to homogenous to be isolated. Electron microscopic studies showed that all PLP were assembled at early stages of sporulation, while immunoprecipitation showed that at least in B. medusa and subsp. israelensis, the PLP proteins are synthesized at the times the PLP were assembled.;Acrystalliferous (cry('-)) variants of subsp. israelensis isolated by a 42(DEGREES)C curing method were found to produce, upon sporulation, a satellite inclusion (sat) which was subsequently found in the wild type. Cry('-)sat('+) variants were (SLASHCIRC)isr-1 producing while cry('-)sat('-) variants were not. The latter strains also lacked a 68MDa plasmid of the wild type. A cry('+)sat('-) strain was (SLASHCIRC)isr-1 producing. Examination of transformed strains of a cry('-)sat('-) and plasmidless variant revealed that the sat('+) and (SLASHCIRC)isr-1 producing characters could have been co-transformed in a recipient strain which had acquired the 68 MDa plasmid; likewise, the cry('+) and (SLASHCIRC)isr-1 producing characters could have been co-transformed in a strain which had acquired the 75 MDa plasmid known to be associated with the synthesis of the crystal.;B. thuringiensis isolate 73-E-10-2 produced inclusions of varying size. The size distribution of the inclusions was influenced by the composition of the medium and the growth temperature. Inclusions prepared from cultures with higher number of small inclusions-producing cells have relatively less of a 25.5 K proteins and two smaller proteins. These inclusion preparations were also less toxic than those preparations with more of these three proteins. Variants producing solely small non-toxic inclusions lacking the above three proteins and a 140 K protein were devoid of (SLASHCIRC)10-2-1.;The results of this study indicated that the genes responsible for the syntheses of (SLASHCIRC)isr-1 and (SLASHCIRC)10-2-1 could be located on plasmids which also carried the genes determining the syntheses of components of the inclusions. (Abstract shortened with permission of author.)



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