Occurrence of Non-Insecticidal Bacillus thuringiensis Flagellar Serotype 14 in the Soil of Japan

Abstract

Summary Three spore-forming isolates obtained from a soil sample of Hokkaido Island, Japan, were referable to Bacillus thuringiensis flagellar (H) serotype 14 (subsp. israelensis). Parasporal inclusions of these isolates were morphologically very similar to those produced by the type strain of B. thuringiensis H serotype 14. The type strain of H serotype 14 was highly virulent to aedine and culicine mosquito larvae, while the three isolates were avirulent to mosquito larvae. Immunologically, there was no relationship between parasporal inclusion proteins of the type strain and the three avirulent isolates. A great difference was observed in sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles of parasporal inclusion proteins. Parasporal inclusions of the type strain contained proteins with molecular masses of 130 kD, 70 kD, 38 kD, and 24 kD, while those of the avirulent isolates contained proteins of 47 kD, 36 kD, 30 kD, and 24 kD and a few minor proteins. The results suggested that the avirulent property of the H serotype 14 isolates was attributable to the lack of 130-kD protoxin in their parasporal inclusions.