الفهرس 
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Abstract
1. Characterization of Bacillus thuringiensis (B.t)
1.1. History and application
Microbial pesticides which were developed to avoid the toxicity
associated with many chemical pesticides have been used for large scale
pest control for more than three decades. The chief organism used for
this purpose is Bacillus thuringiensts (B. t.). This bacteria was originally
isolated from morbid silkworm moth, Bombyx mori, Lepidoptera larvae
more than a centuty ago(l). Ten years later, a similar organism was
isolated from Mediterranean flour moth, Ephestia kuehniella(2). In 1911
this bacteria was identified as the cause of death in flour moth larvae,
Golleria melonella, (Lepidoptera) and gave this organism the name
Bacillus thuringiensis/”. Later a B. t. strain isolated from the yellow
mealworm beetle, Tenebrio molitor was found to be toxic to larvae of the
Colorado beetle, Leptinotarsa decemlineata, (Coleoptera) and of other
beetles as well(3).
Today there are strain collections that contain several thousand B. t.
isolates’i’”. Because they are highly effective against pests prominent in
agriculture and forestry, many B. t. products are now used for pest control
(Table 1.1). They act selectively against specific pests without harming
beneficial organisms and are very safe for the user. Success of B.t. is due
to the high efficacy of its insecticidal proteins, the existence of a
diversity of proteins that are effective against a range of important pests;
its relative safety to non target insect predators and parasites, its ease of
mass production at relatively low cost, and its adaptability to
conventional formulation and application technology.