الفهرس 
Materials and MethodsOnly 14 pages are availabe for public view
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Abstract
The present work was devoted to the isolation of entomopathogenic strains of Bacillus sphaericus
from Egyptian environments, their characterization, identification and the elucidation of the
physiological factors affecting their growth, and toxin production. Special attention was paid to
the application of modem genetic engineering approaches for illustrating their taxonomic position
in reference to present classifications as well as the study of possible relationships between
sporulation and toxin formation. An investigation on possible production of the mosquitocidal toxin
from indigenous strains using locally available agro-industrial by-products in comparison to an
international strain, was carried out.
The obtained results have shown that some of the local isolates were highly toxic to
mosquito(}larvae and possessed the typical ribotype pattern of known pathogenic B. sphaericus
strains (homology group IIA). While some low toxic Egyptian isolates possessed a unique ribotype
pattern that was different from the typical pattern of pathogenic strains. Furthermore, some
isolates with low toxicity and have Mtx toxin, when serologically classified, were found to belong
to serotypes 27, 5a5b, 9a9b and 26a26b. Serotypes 27, 5a5b and 9a9b
were not known before to include low pathogenic strains .while
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serotype 26a26b was known to have strains that lack both toxin genes.
The obtained results have also shown that sporulation process was essential for crystal toxin
formation. Expression of sigma factor cl is responsible for toxin production in stage II and
continued until stage
III of sporulation.
Physiological studies have revealed that some factors influenced the production of the binary toxin
of Bacillus sphaericus. Such factors included phosphate concentrations, level of trace elements in
the growth medium as well as aeration extents and incubation temperatures.
Comparative fermentation studies usmg an indigenous Egyptian strain as well as a standard
international strain grown on media made of leguminous seeds and locally available agro-industrial
by-products gave excellent growth and high yields of mosquitocidal toxins. Best results of the
fermentation studies were obtained upon the use of the Egyptian strain when grown on soy flour,
cottonseed flour, offals meal and backing yeast as complete media for toxin production. The
obtained results were discussed in the light of their application
· feasibility regarding the possible local production of the mosquitocidal toxins from the highly
potent indigenous strain grown on local agroindustrial byproducts and leguminous seeds in Egypt.