Insertional inactivation of hblC encoding the L-2 component of Bacillus cereus ATCC 14579 haemolysin BL strongly reduces enterotoxigenic activity, but not the haemolytic activity against human erythrocytes

Haemolysin BL (HBL) is a Bacillus cereus toxin composed of a binding compon ent, B, and two lytic components. L-1 and L-2. HBL is also the enterotoxin responsible for the diarrhoeal food poisoning syndrome caused by several st rains of B. cereus. The three genes encoding the HBL components constitute an operon and are transcribed from a promoter 608 bp upstream of the hblC t ranslational start site. The first gene of the hbl operon, hblC. in the B. cereus type strain. ATCC 14579, was inactivated in this study. Inactivation of hblC strongly reduced both the enterotoxigenic activity of a. cereus AT CC 14579 and the haemolytic activity against sheep erythrocytes, while main taining full haemolytic activity against human erythrocytes.