The present invention pertains to the discovery that B. anthracis possesses a luxS gene that encodes a functional LuxS polypeptide, and that B. anthracis synthesizes a functional AI-2 quorum-sensing molecule. The invention provides mutant B. anthracis bacteria lacking the function of the luxS gene, which do not produce a functional AI-2 molecule and have growth defects compared to wild-type B. anthracis. The invention also concerns methods for inhibiting the growth of B. anthracis, or for preventing or treating B. anthracis infection, by inhibiting the activity of the B. anthracis LuxS polypeptide, or by exposure of the B. anthracis to furanone. In particular, the invention concerns the use of furanone, a compound that inhibits AI-2-mediated quorum-sensing, to inhibit the growth of B. anthracis, to inhibit B. anthracis toxin production, particularly that of protective antigen, and to prevent or treat B. anthracis infection. The invention also provides methods to prevent B. anthracis infection, or enhance an immune response to B. anthracis infection, by administering a vaccine comprising a B. anthracis cell in which the luxS gene is mutated.