Sporulation of Bacillus sphaericus 2297: an electron microscope study of crystal-like inclusion biogenesis and toxicity to mosquito larvae.
Sporulation of Bacillus sphaericus strain 2297 in a synchronous liquid culture was studied by electron microscopy. The t0 of sporulation occurred 7 h after the beginning of the lag phase. Crystal-like inclusions first appeared at t2 and reached their final size between t5 and t6. The release of the spore/inclusion complex occurred at about t15 (22 h after inoculation). Toxicity against Culex pipiens larvae was related to sporulation and appeared during the early stages of sporulation. The LC50 (24 h) decreased about 10(5)-fold between t0-2 and t7, in correlation with the formation of crystalline inclusions. Heat resistance of spores appeared later than toxicity.
D000818:Animals; D001407:Bacillus / Q000502:physiology* / Q000648:ultrastructure; D003460:Crystallization; D003465:Culex / Q000254:growth & development*; D007814:Larva / Q000254:growth & development; D008854:Microscopy, Electron; D009032:Mosquito Control; D013171:Spores, Bacterial / Q000648:ultrastructure