STRATEGIES FOR INACTIVATING BACILLUS ANTHRACIS SPORES

炭疽芽孢杆菌是一种潜在的动物和人类病原体

Bacillus anthracis is an animal and human pathogen with potential as a biological warfare agent. It is a spore-forming Bacillus with pathogenicity due to plasmid genes encoding three toxin components and a polyglutamic acid capsule. Its effectiveness as an agent is due to the ease of producing and spreading the spores. These spores are dormant and very resistant to a variety of stress conditions such as heat, ultraviolet radiation, and chemical treatment. The spores can thus remain in the soil or phylloplane for many years. Under suitable conditions, they can germinate and vegetative cells will propagate in the soil and then resporulate. Thus, there is an enormous potential for sustaining and spreading this organism once it has been dispersed. The spore is surrounded by a multilayered proteinaceous coat that accounts for much of its resistance properties and contributes to the capacity of the spore to respond to germinants and propagate as vegetative cells. A detailed understanding of the spore coat structure, how it is assembled, and how it can be specifically disrupted would provide an effective way for controlling this bioweapon. Information gleaned from extensive studies of Bacillus subtilis spore coat assembly and the function of the 25 or so proteins that make up the coat layers of this species will be used to isolate and characterize spore coat protein genes from B. anthracis. This will be done in part by identifying B. subtilis homologues in the B. anthracis genome and in part by reverse genetics using the amino acid sequences of purified B. anthracis coat proteins. These genes will be disrupted and the effects of such null mutations on spore coat assembly and structure determined. Some features of the B. anthracis spore such as germination response and spore coat structure have been shown to vary with the conditions used for spore formation. Most significantly, culture conditions that induce many pathogenicity genes, including the toxin genes, resulted in a major change in the spore coat protein profile. This correlation may reflect coordination between pathogenicity due to toxin synthesis and encapsulation of vegetative cells and special spore properties that could enhance infectivity. The nature of the spore coat changes and their contribution to spore germination and resistance will be examined. This information about spore coat composition and its variation with culture conditions will be exploited to find specific reagents and procedures for destroying the spore or for inhibiting germination. Once such reagents or methods have been identified, they will be tested on spores in various soils that should mimic natural environments and thus the conditions needed for the effective control of this bioweapon.