Biogenesis of the Crystalline Inclusion of Bacillus thuringiensis during Sporulation

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Abstract
The biogenesis of the crystalline inclusion of Bacillus thuringiensis has been studied in the more general context of sporulation and in regard to the formation of some spore constituents. It has been shown that crystal protein is essentially formed during stages III and IV, before the acquisition of octanol resistance. One fraction of protein spore coats which is solubilized by a reducing agent associated with urea or guanidine hydrochloride, is synthesised at the same time; a more insoluble cystine‐rich fraction is formed later, during stage V, just before the heat resistance is reached.The analysis of bacterial extracts at intervals during sporogenesis indicates preferential synthesis of insoluble proteins (or proteins bound to membraneous structures), crystal protein represents a large proportion of these proteins. Immunological characterisation of crystal protein, with autoradiographic experiments reveals at least three antigens produced simultaneously after t4 and continuously throughout the biogenesis.The sporulation of a mutant non crystal bearing strain was studied; it has been shown that this mutant accumulates soluble proteins having some of the properties of crystal constituents; in this case the synthesis and maturation of spore coats arise earlier in the course of sporulation than in the wild strain.All results suggest a relation between crystal protein and a protein fraction of the spore coats.