Structure, diversity, and evolution of protein toxins from spore-forming entomopathogenic bacteria

Gram-positive spore-forming entomopathogenic bacteria can utilize a large variety of protein toxins to help them invade, infect, and finally kill their hosts, through their action on the insect midgut. These toxins belong to a number of homology groups containing a diversify of protein structures and modes of Action. In many cases; the toxins consist of unique folds or novel combinations of domains having known protein folds. Some of the toxins display a similar structure and mode of action to-certain toxins of mammalian pathogens" suggesting a common evolutionary origin. Most of these toxins are produced in large amounts during sporulation and have the remarkable feature that they are localized in parasporal crystals. Localization of multiple toxin-encoding genes on plasmids together with mobilizable elements enables bacteria to shuffle their armory of toxins. Recombination between, toxin genes and sequence divergence has resulted in a wide range of host specificities.