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Our goals are to purify and determine the biological activities of two variant forms of HBL from strains SIC and MGBC 145. Components will be purified, and tested for enterotoxin activity by the vascular permeability assay and for hemolytic activity. N-terminal sequences of the purified components as well as of internal peptides produced by limited proteolysis of the components will be determined to assess whether the different forms represent unprocessed versions of the same gene product or different gene products.
The diarrheal food poisoning caused by Bacillus cereus is poorly understood. B. cereus is naturally present in a wide variety of raw and processed foods. It produces spores that are not readily killed by normal cooking procedures. Many strains can grow at refrigeration temperatures, presenting a major problem in the control of this organism in our food supply. Our long term goals are to determine the public health significance of foods contaminated with B. cereus. We have shown that hemolysin BL (HBL) is a diarrheal enterotoxin produced by B. cereus. It is composed of three distinct protein components, B, L1, and L2 (37.8, 38.5, and 43.2 kDa, respectively, from prototype strain F837/76); all three are required for biological activity. Recently, we found distinct variations in each component among strains. The significance and relative toxicity of the multiple HBL forms is unknown. Our goals are to purify and determine the biological activities of two variant forms of HBL from strains SIC and MGBC 145. Components will be purified, and tested for enterotoxin activity by the vascular permeability assay and for hemolytic activity. N-terminal sequences of the purified components as well as of internal peptides produced by limited proteolysis of the components will be determined to assess whether the different forms represent unprocessed versions of the same gene product or different gene products. Results obtained will be useful in determining whether multiple forms of HBL are biologically active, and the extent B. cereus isolates would pose a significant food safety threat.