Bacillus popilliae and Bacillus lentimorbus, bacteria causing milky disease in Japanese beetles and related scarab larvae

Abstract

Bacillus popilliae and Bacillus lentimorbus, causative agents of milky disease in Japanese beetle and related scarab larvae, have hitherto been differentiated based upon a small number of phenotypic characteristics, but they have not previously been examined at the molecular level. In this study 34 isolates of these bacteria were examined for DNA similarity and by random amplified polymorphic DNA (RAPD) analysis. Two distinct but related similarity groups were identified: the first contained strains of B. popilliae and the second contained strains of B. lentimorbus. Two strains distinct from but related to B. popilliae may represent a subspecies. Some strains received as B. popilliae were found to be most closely related to B. lentimorbus and some received as B. lentimorbus were found to be most closely related to B. popilliae. RAPD analysis confirmed the DNA similarity results. Paraspore formation, previously believed to be a characteristic unique to B. popilliae, was found to occur among a sub-group of B. lentimorbus strains. Growth in media supplemented with 2% NaCI was found to be a somewhat less reliable characteristic in distinguishing the species than vancomycin resistance, the latter being present only in B. popilliae.