Mechanisms of killing of Bacillus thuringiensis Al Hakam spores in a blast environment with and without iodic acid

Aims: To determine the mechanism of killing of spores of Bacillus thuringiensis Al Hakam, a Bacillus anthracis spore surrogate, in a blast environment with or without HIO₃ and whether the spores are truly dead.

Methods and results: Spores exposed to an aluminium-based blast environment with or without HIO₃ with dynamic peak gas phase temperatures near 1000°C persisting for 10's of ms, were killed 97 and 99·99% without and with HIO₃ respectively and the spores were truly dead. The survivors of the detonations did not acquire mutations, did not become wet heat sensitive, became sensitive to elevated NaCl but not lack of glucose in recovery media, and many dead spores remained phase bright and retained their Ca-dipicolinic acid. A large fraction of the dead spores could germinate, but most of these germinated spores were dead.

Conclusions: Most spores exposed to a blast environment are truly dead, and HIO₃ increases spore death. The likely mechanism of spore killing in these blast environments is damage to some essential spore protein, although spore inner membrane damage could contribute.

Significance and impact of the study: This work shows that spores of a surrogate for B. anthracis spores are killed in a blast environment without or with HIO₃ present, this approach could inactivate up to 99·99% of dry B. anthracis spores, and the spores are likely killed by damage to some essential spore protein.