MIC231, a Mobile Insertion Cassette from Bacillus cereus

摘要

Bacillus cereus sensu lato refers to four related soil bacteria known as B. cereus (sensu stricto), B. thuringiensis, B. mycoides and B. anthracis. although sharing the same genetic background, these bacteria appearently display a flexible genomic organization: the chromosomal size varied from 2.4 to more than 5.5 Mb among the various strains, and in some cases, at least part of the "missing" chromosomal DNA could be detected as extrachromosomal molecules (Carlson and Kolsto, 1994). The presence of numerous plasmids has also been documented in many strains, but very little is known about their possible functions and biological roles. Similarly, many transposable elements have been characterized in all members of the B. cereus group: more than 20 putative mobile elements have been reported, including both Insertion Sequences (IS) and class II transposons (Mahillon et al., 1994). Among these, the best characterized element is IS231. Originally isolated from B. thuringiensis, IS231 was also found in B. cereus, B. mycoides and on the virulence plasmids of B. anthracis (Leonard et al., 1997). this element belongs to the IS4 family (Mahillon and Chandler, 1998) and more than 15 iso-IS231 have been described, with by two size-classes of 1.6 and 1.9 kb.