A physical and genetic map of the Bacillus thuringiensis subsp, berliner 1715 (serotype 1) chromosome was constructed by pulsed field gel electrophoresis using three restriction enzymes, Asci, Notl and Sfil. A total of 24 restriction enzyme sites and 28 probes were located on the map. The chromosome size was 5.7 Mb. Consistent with previous mapping of Bacillus cereus chromosomes, the genes were nonrandomly distributed. Genes which are often plasmid-encoded were located on one half of the chromosome, whereas the other half contained rRNA genes and the origin region. Hybridization with macro-restriction fragments showed that the region containing rRNA genes and the origin was similar to that of the B. cereus type strain, ATCC 14579, and confirmed that the region was conserved between the B. cereus and B. thuringiensis chromosomes. The insecticidal toxin probe crylA or the transposon probe Tn4430 hybridized to six extrachromosomal elements of 60, 60, 100, 130, 270 and 600 kb, indicating that the genome size was at least 6.9 Mb.
