Some functional genes have been disrupted through the insertion of ISs, preferentially IS231C. By comparing the Southern hybridization profiles of different B. thuringiensis strains, the existence of ISBth166 was mainly found in serovar kurstaki and the recent expansion of IS231C between different kurstaki isolates was suggested. In addition to revealing the ISs profile in YBT-1520 as well as the comparison in the B. cereus group, this study will contribute to further comparative

analyses of multiple B. thuringiensis strains aimed at understanding the IS-mediated genomic rearrangements among them. The Bacillus cereus group consists of a group of gram-positive endospore-forming bacteria belonging to the Firmicutes phylum. PLX3397 These species have a huge impact on human activities due to their pathogenic properties and/or economic importance, such as Bacillus anthracis, the causal agent of anthrax, which can be lethal to humans and other mammals; B. cereus, an opportunistic human pathogen involved in food-poisoning incidents and contaminations in hospitals (Drobniewski,

1993); and Bacillus thuringiensis, an insect pathogen that is widely used as a leading biorational pesticide (Schnepf et al., 1998). These three species are very closely related at the genomic level and were strongly suggested to represent one species on the basis of genetic evidence (Rasko et al., 2005; Tourasse et al., 2006). The only established difference between B. cereus and B. thuringiensis strains is the presence of genes coding for the insecticidal toxins, usually Navitoclax present on plasmids (Helgason et al., 2000). Eighteen B. cereus group genomes have been completely sequenced and published in GenBank. Insertion sequences (ISs) are small transposable DNA fragments consisting of, in general, a unique transposase-encoding gene and terminal inverted repeats (IRs), which serve as the sites PAK6 for recognition and cleavage by transposases (Tpases) (Mahillon & Chandler, 1998). A large number of ISs have been

classified into 22 families mainly based on the amino acid sequence similarities of their Tpases (Siguier et al., 2006a). ISs played an important role in genome reshuffling and evolution by facilitating horizontal gene transfer and mediating homologous recombination between multiple copies present in a given genome (Mahillon et al., 1999). The diversity and distribution of some well-known ISs that are generally structurally associated with genes coding for parasporal crystal proteins in B. thuringiensis have been widely studied (Mahillon et al., 1994; Leonard et al., 1997; Rosso & Delecluse, 1997; Joung & Cote, 2003; Huang et al., 2004). However, the entire ISs content of the B. thuringiensis genome has never been reported. Bacillus thuringiensis ssp.