Isolation and partial characterization of the parasporal body of Bacillus popilliae

The sporangial wall of Bacillus popilliae encloses a spore and parasporal body and is very resistant to breakage. High-energy sonication can disrupt this envelope and release free spores and parasporal bodies which retain refractility. Parasporal bodies, free spores, and sporangial debris were separated by centrifugation in linear sucrose gradients. Purified parasporal bodies are proteinaceous. Of the 17 amino acids detected, glutamic and aspartic acids are highest in concentration and account for the low isoelectric point of 4.5; a lipid moiety was not found. Parasporal bodies are soluble in 0.1N NaOH, 8M guanidine hydrochloride, 8M urea, or alkaline thioglycollate. Paper electrophoresis at 3000 V separated soluble parasporal protein into three cathodic components. Solubilized or whole intact parasporal bodies fed to third-instar larvae of the Japanese beetle were not detectable toxic. However, solubilized parasporal protein was twice as toxic as the intact parasporal bodies when injected into the hemocoel.