Comparison of cytotoxin cytK promoters from Bacillus cereus strain ATCC 14579 and from a B. cereus food-poisoning strain.

The cytotoxin CytK produced by Bacillus cereus is believed to be involved in food-borne diseases. The transcriptional activity of the cytK promoter region in a food-poisoning strain was studied using a reporter gene and compared with that in the reference B. cereus strain ATCC 14579. In the food-poisoning strain, cytK is more strongly transcribed, possibly explaining the pathogenicity. The global regulator PlcR in B. cereus controls several putative virulence factors. It was found that PlcR regulates cytK in this clinical strain despite a mismatch in the PlcR recognition site, as currently defined. This suggests that the PlcR box consensus should be reconsidered and that the PlcR regulon might be larger than suspected. It is also shown that the high level of cytK transcription is not caused by a modification in the PlcR recognition site.