Four plasmids simultaneously maintained in bacillus cereus, a tetracycline-resistant isolate

We have isolated a tetracycline-resistant (Tc^r) Bacillus species (named HE-1) which carries multiple plasmids. HE-1 was identified as Bacillus cereus and found to bear four plasmids. Tetracycline resistance could be attributed to one of four plasmids (designated as pTITβ2 (4.7 kb)) indistinguishable from pBCI6, a Tc^r plasmid formerly found in B. cereus [K. Bernhard, H. Schrempf, and W. Goebel, J. Bacteriol., 133, 897 (1978)]. All the other three plasmids (named pTITα (4.0kb), pTITβ1 (4.7kb) and pTITγ (12.4kb)) were cryptic and did not correlate with bacterial phenotypic traits such as antibiotic resistance or antibiotic and bacteriocin production. B. cereus HE-l alsb showed resistance to penicillin, but this seemed very likely to be chromosomally determined in B. cereus. Of interest was the fact that pTITα, pTITβ1, and pTiTγ had a noticeable DNA homology among them in blot hybridization. pTITβ2 alone did not shared sequence homology with the other three plasmids.