Manasherob R, Ben-Dov E, Zaritsky A, Barak Z
Department of Life Sciences, Ben-Gurion University of the Negev, Be'er-Sheva, Israel.
Appl Environ Microbiol. 1998 May;64(5):1750-8. doi: 10.1128/AEM.64.5.1750-1758.1998.
Spores of Bacillus thuringiensis subsp. israelensis and their toxic crystals are bioencapsulated in the protozoan Tetrahymena pyriformis, in which the toxin remains stable. Each T. pyriformis cell concentrates the spores and crystals in its food vacuoles, thus delivering them to mosquito larvae, which rapidly die. Vacuoles containing undigested material are later excreted from the cells. The fate of spores and toxin inside the food vacuoles was determined at various times after excretion by phase-contrast and electron microscopy as well as by viable-cell counting. Excreted food vacuoles gradually aggregated, and vegetative growth of B. thuringiensis subsp. israelensis was observed after 7 h as filaments that stemmed from the aggregates. The outgrown cells sporulated between 27 and 42 h. The spore multiplication values in this system are low compared to those obtained in carcasses of B. thuringiensis subsp. israelensis-killed larvae and pupae, but this bioencapsulation represents a new possible mode of B. thuringiensis subsp. israelensis recycling in nontarget organisms.
苏云金芽孢杆菌以色列亚种的孢子及其有毒晶体被原生动物梨形四膜虫进行生物包囊，毒素在其中保持稳定。每个梨形四膜虫细胞将孢子和晶体浓缩在其食物泡中，从而将它们传递给蚊子幼虫，蚊子幼虫会迅速死亡。含有未消化物质的液泡随后从细胞中排出。通过相差显微镜和电子显微镜以及活细胞计数，在排出后的不同时间确定食物泡内孢子和毒素的命运。排出的食物泡逐渐聚集，7小时后观察到苏云金芽孢杆菌以色列亚种的营养生长，形成从聚集体长出的丝状物。生长出的细胞在27至42小时之间形成孢子。与在苏云金芽孢杆菌以色列亚种杀死的幼虫和蛹的尸体中获得的孢子增殖值相比，该系统中的孢子增殖值较低，但这种生物包囊代表了苏云金芽孢杆菌以色列亚种在非靶标生物中循环利用的一种新的可能模式。
