The cytolytic agent(s) within the Bti/Btk-vegetative cell exoprotein (VCP) pool is an early spore outgrowth product identical to that of B.
50], was [is less than] 4 hr at 37 [+ or -] 3 [degrees] C (the optimum Btk or Bti spore outgrowth temperature) and because 5-20% of these spores remained viable, even under the harshest pH and temperature conditions used by the human body defense system (2), these spores have the potential to survive and also to propagate in an in vivo mammalian environment.
Spore outgrowth from BT products as well as from the controls, B.
Enumeration of the shed cells based on separate exposure assays (n = 20) revealed that 43 [+ or -] 12% of the cells had degraded beyond recognition as long as one spore was present per assay well and its outgrowth was permitted.
Exposures to intact or solubilized PIBs and the liquid, particulate-free fractions of BT products (Figures 4 and 6) caused little human cell damage as compared to that seen whenever spores were present and their outgrowth was not prevented by antibiotic.