The bacteriophage GIL01 is a temperate phage of the Tectiviridae family that infects the bacterium Bacillus thuringiensis serovar israelensis. GIL01 is a linear prophage that replicates independently of the bacterial chromosome. The genome of GIL01 comprises of 14931 bp and 30 ORF. Genes with similar function are located together. The P1 and P2 promoters regulate the expression of genes for genome replication and transcription (ORF1-ORF8). The P3 promoter regulates the expression of genes for host recognition, assembly of the capsid, and lysis of the host (ORF9-ORF30). The promotor regions carry four binding sites for the host transcription repressor LexA, named as dinBox sites that are important for GIL01 lysogeny. The ends of GIL01 genome carry 73 bp terminal repeats with covalently bound terminal proteins that are important for genome replication. The bacteriophage gene products can regulate host sporulation. Bacterial spores provide bacteriophages protection and enable DNA repair in spores, as well as a means of phage dissemination. Previous results at the Department of Biochemistry have shown that GIL01 lysogeny restores sporulation of the otherwise asporogenic strain Bacillus thuringiensis serovar israelensis GBJ002. The determinant or regulator of GIL01 that influences host sporulation has not yet been identified. The GIL01 sporulation regulator of B. thuringiensis serovar israelensis was expected to be located in the first operon (ORF1-ORF8), in the regulatory domain of the GIL01 genome. By molecular cloning of the GIL01 genomic regions ORF1-ORF8, P1P2ORF1-ORF8, ORF9-ORF22 and ORF23-ORF30 into the plasmid vector pDG148 and the sporulation test, we showed that the entire GIL01 genome or GIL01 lysogeny is required for sporulation regulation. Expression of the ORF1-ORF8 or ORF9-ORF22 or ORF23-ORF30 gene products has a negative effect on host cells.
|
