Abstract
The sigE and sigK genes, encoding the sporulation-specific sigma factors sigma 35 and sigma 28 of Bacillus thuringiensis, were each disrupted by inserting a gene conferring resistance to kanamycin into their coding sequences. The B. thuringiensis SigE- and sigK- mutant strains were blocked at different sporulation stages and were unable to sporulate. The SigE-strain was blocked at stage II of sporulation, whereas the SigK- strain was blocked at stage IV. The expression of a cryIAa'-'lacZ transcriptional fusion was analysed in these genetic backgrounds and it was found that both sigma factors are involved in the in vivo transcription of this gene. However, the SigK- strain harbouring the cryIAa gene produced amounts of toxin similar to those produced by the B. thuringiensis Spo+ strain. The toxins accumulated in the mother cell compartment to form a crystal inclusion which remained encapsulated within the cell wall. Thus, transcription from the sigma E-dependent promoter alone (Bt I promoter) is sufficient to support high levels of toxin production in B. thuringiensis.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Bacillus thuringiensis / genetics*
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Bacillus thuringiensis / metabolism
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Bacillus thuringiensis / physiology
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Bacillus thuringiensis / ultrastructure
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Bacillus thuringiensis Toxins
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Bacterial Proteins / biosynthesis
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Bacterial Proteins / chemistry
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Bacterial Proteins / genetics*
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Bacterial Proteins / physiology
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Bacterial Toxins / biosynthesis
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Bacterial Toxins / genetics*
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Base Sequence
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DNA Primers
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Electrophoresis, Polyacrylamide Gel
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Endotoxins / biosynthesis
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Endotoxins / chemistry
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Endotoxins / genetics*
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Gene Expression Regulation, Bacterial / genetics
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Hemolysin Proteins
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Kanamycin / pharmacology
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Lac Operon
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Microscopy, Electron
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Molecular Sequence Data
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Mutagenesis, Insertional
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Pest Control, Biological
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Promoter Regions, Genetic
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Recombinant Fusion Proteins / biosynthesis
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Sigma Factor / genetics*
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Sigma Factor / physiology
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Spores, Bacterial / physiology
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Transcription Factors / genetics*
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Transcription Factors / physiology
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Transcription, Genetic / genetics
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beta-Galactosidase / metabolism
Substances
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Bacillus thuringiensis Toxins
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Bacterial Proteins
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Bacterial Toxins
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DNA Primers
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Endotoxins
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FliA protein, Bacteria
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Hemolysin Proteins
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Recombinant Fusion Proteins
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Sigma Factor
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Transcription Factors
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insecticidal crystal protein, Bacillus Thuringiensis
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sporulation-specific sigma factors
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Kanamycin
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beta-Galactosidase