Cytotoxic potential of industrial strains of Bacillus sp

The cytotoxic potential of selected strains of Bacillus licheniformis, Bacillus amyloliquefaciens, and Bacillus subtilis, used in the production of industrial enzyme products, has been assessed. Cytotoxicity was determined in Chinese hamster ovary (CHO-K1) cells by measuring total cellular metabolic activity using the tetrazolium salt 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). Initially the MTT assay was validated against toxigenic strains of Bacillus cereus, to define the exact criteria for a toxigenic versus a nontoxigenic response. The assay proved sensitive to culture broths of both a diarrheagenic strain and an emetic strain of B. cereus. The enzyme-producing strains tested were nontoxic to CHO-K1 cells. Additionally it was demonstrated that our industrial strains did not react with antibodies against B. cereus enterotoxins by use of commercial antibody-based kits from Oxoid and Tecra. A short survey of the literature concerning the toxigenic potential of species within the subtilis group is included, as is a database search of known B. cereus enterotoxins against B. subtilis and B. licheniformis DNA sequences.