Small Plasmids from Bacillus thuringiensis: Genetic Comparison of six Plasmids from two Different Strains

摘要

Members of the B. cereus- group display a large variety of plasmids. These plasmids belong to one of two groups: the smaller plasmids (< 15 kb) which, like most other small Gram-positive plasmids use rolling-circle replication (RCR), and the large plasmids in which replication occurs through the theta mode of replication (Wilcks et al., 1999). the insecticidal toxins, characteristic of the B. thuringiensis strains, are encoded by large conjugative or mobilizable plasmids and the genetic basis for the virulence factors of B. anthracis are also located on plasmids. However, so far, no plasmids have been associated with virulence in B. cereus. In addition to the toxin gene-bearing plasmids, B. thuringiensis strains harbour a complex array of cryptic plasmids.