Novel Clostridium botulinum toxin gene arrangement with subtype A5 and partial subtype B3 botulinum neurotoxin genes.

摘要

Botulinum neurotoxin, the most poisonous substance known and a potential biothreat agent (1), causes human and animal botulism worldwide (4, 9). This toxin is encoded by the bont gene as part of a cluster that includes nontoxic accessory genes (10). Two main gene clusters are known: the hemagglutinin-containing (ha+) cluster in toxin serotypes Al, B, C, D, and G and the orfX cluster in toxin serotypes A, E, and F (7, 10). In addition, some Clostridium botulinum type A strains (e.g., NCTC2916) contain a silent type B gene in their chromosome, designated A(B). The silent B toxin genes described to date contain the full length of the active type B gene cluster and one or more mutations that result in an unexpressed type B neurotoxin (3, 8).