Two different parasporal inclusions are produced by Bacillus thuringiensis subsp. finitimus

Abstract

Bacillus thuringiensis subsp. finitimus produced at least two parasporal inclusions. One inclusion was formed within the exosporium and remained with the spore after mother cell lysis. A second inclusion formed somewhat later exterior to the exosporium. Each inclusion contained a major polypeptide of about 135,000 daltons with unique antigenic determinants. This subspecies contained only two plasmids, of 98 and 77 megadaltons (MDa). Strains cured of these plasmids produced only the free inclusion. Since the plasmid-cured strains did not contain DNA sequences homologous to plasmid DNA, the gene for the free-inclusion protein must be encoded in the chromosome. In contrast, the enclosed parasporal inclusion was produced only when the plasmid of 98 MDa was present. In addition, transfer of the 98-MDa plasmid to Bacillus cereus resulted in transcipients that produced small inclusions enclosed within the exosporium, and the protein extracted from these inclusions reacted with antibody specific for enclosed inclusion protein of B. thuringiensis subsp. finitimus. Genes in both the chromosome and a plasmid function in the synthesis of distinct parasporal proteins in this subspecies.