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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.
Insights
Bacillus thuringiensis subsp. finitimus produces two types of parasporal inclusions, with distinct genes located on both the chromosome and a 98 MDa plasmid, controlling their synthesis and unique protein structures.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Bacillus thuringiensis subspecies produce parasporal inclusions, which are proteinaceous crystals with insecticidal properties.
- The genetic basis for the production of these inclusions can involve both chromosomal and plasmid-borne genes.
Purpose of the Study:
- To investigate the genetic control of two distinct parasporal inclusions produced by Bacillus thuringiensis subsp. finitimus.
- To determine the role of plasmids in the synthesis of these inclusions.
Main Methods:
- Plasmid curing experiments to generate strains lacking specific plasmids.
- Analysis of parasporal inclusion production in plasmid-cured and wild-type strains.
- DNA hybridization to assess gene localization.
- Plasmid transfer experiments to Bacillus cereus.
Main Results:
- Bacillus thuringiensis subsp. finitimus produces two parasporal inclusions: one enclosed within the exosporium and one free.
- Strains cured of plasmids produced only the free inclusion, indicating its gene is chromosomal.
- The 98 MDa plasmid was essential for the production of the enclosed inclusion.
- Transfer of the 98 MDa plasmid to Bacillus cereus resulted in the production of enclosed inclusions.
Conclusions:
- Distinct parasporal proteins in Bacillus thuringiensis subsp. finitimus are synthesized through the coordinated action of chromosomal and plasmid genes.
- The 98 MDa plasmid carries the gene for the enclosed parasporal inclusion protein.
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