Behavior of milky disease organisms in a tissue culture system.

Abstract Milky disease organisms were studied in vitro in a tissue culture medium containing hemocytes of Phyllophaga anxia . The pathogens were two European isolates, Bacillus fribourgensis and Bacillus popilliae melolontha , from Melolontha melolontha and Bacillus popilliae , the causative agent of milky disease in Popillia japonica . All three pathogens were able to germinate and to develop good vegetative growth. Spores, however, were formed only by the European isolates. The in vitro sporulation process is described and compared with the in vivo development of milky disease spores. As soon as the spores were mature they were phagocytized by the hemocytes. A similar phagocytic action could be observed in vivo. Under certain conditions hemocytes might successfully block an infection caused by milky disease organisms.