New flagellar (H) antigenic subfactors in Bacillus thuringiensis H serotype 3 with description of two new subspecies, Bacillus thuringiensis subsp. sumiyoshiensis (H serotype 3a:3d) and Bacillus thuringiensis subsp. fukuokaensis (H serotype 3a:3d:3e)

Abstract

Flagellar (H) antigenic structures of the following four strains of Bacillus thuringiensis H serotype 3 were investigated: the type strains of B. thuringiensis subsp. alesti and B. thuringiensis subsp. kurstaki and two soil isolates, 84-F-26-3 and 84-F-51-46. Cross-saturation of H antisera with heterologous H antigens revealed the presence of five H antigenic subfactors (3a, 3b, 3c, 3d, and 3e) in this serotype. H antigenic structures of the type strains of subsp. alesti and subsp. kurstaki (formerly H serotypes 3a and 3a:3b, respectively) were 3a:3c and 3a:3b:3c, respectively. Soil isolates, 84-F-51-46 and 84-F-26-3, had H antigenic structures of 3a:3d and 3a:3d:3e, respectively. These two isolates, which produced similar spherical parasporal inclusions, were toxic to larvae of the three lepidopterous species ( Bombyx mori, Hyphantria cunea, and Clostera anastomosis) but nontoxic to larvae of the two mosquito species ( Aedes aegypti and Culex tritaeniorhynchus) and the house fly, Musca domestica. Two new subspecies names, Bacillus thuringiensis subsp. sumiyoshiensis (H serotype 3a:3d) and Bacillus thuringiensis subsp. fukuokaensis (H serotype 3a:3d:3e), are proposed for the type strains, 84-F-51-46 and 84-F-26-3, respectively.