Characterization of a Bacillus anthracis spore coat-surface protein that influences coat-surface morphology

Bacterial spores are encased in a multilayered proteinaceous shell, called the coat. In many Bacillus spp., the coat protects against environmental assault and facilitates germination. In Bacillus anthracis, the spore is the etiological agent of anthrax, and the functions of the coat likely contribute to virulence. Here, we characterize a B. anthracis spore protein, called Cotβ, which is encoded only in the genomes of the Bacillus cereus group. We found that Cotβ is synthesized specifically during sporulation and is assembled onto the spore coat surface. Our analysis of a cotβ null mutant in the Sterne strain reveals that Cotβ has a role in determining coat-surface morphology but does not detectably affect germination. In the fully virulent Ames strain, a cotβ null mutation has no effect on virulence in a murine model of B. anthracis infection.