Ecological Mysteries: is <i>Bacillus thuringiensis</i> a Real Insect Pathogen?

Bacillus thuringiensis ( Bt ) can kill insects and multiply in their bodies, but it can also grow in semi-synthetic media; is found in environments were insects are absent; and has been reported to require midgut-associated bacteria for toxicity. We propose here a novel life cycle for Bt combining insect-based and insect-independent life cycles.