Updating the H-antigen classification of Bacillus thuringiensis

The classification of Bacillus thuringiensis strains has been revised and u pdated based on flagellar antigens which have been in use for many years. S ixty-nine serotypes and 13 sub-antigenic groups have now been identified, g iving 82 serovars among the 3500 B. thuringiensis isolates of the IEBC Coll ection. The number of serovars has gradually increased with the total numbe r of strains. The biochemical characters used have also been investigated a nd their value assessed for identification of B, thuringiensis at the subsp ecies level. A crystal analysis was carried out in terms of morphology, del ta-endotoxin profiles and larvicidal activity for the newly identified sero vars. It was found that atypical crystals, some with novel components, are becoming more common. No insect susceptible to these serovars has been disc overed among known target species. The number of cross-reacting H-antigens among B. cereus strains is increasing and may be of biological significance .