Organisation of the botulinum neurotoxin clusters of Group II C. botulinum Eklund 17B (NRP) and Alaska E43. C. botulinum neurotoxin genes (bont) are located with other associated proteins in one of two types of cluster arrangement. In Group II C. botulinum all published type B neurotoxin genes are in a ha cluster and all type E and type F neurotoxin genes are in an orfX cluster. Eklund 17B and Alaska E43 show typical cluster organisation. A. The neurotoxin gene of Group II C. botulinum type B strain Eklund 17B (NRP) is in a ha cluster located on a plasmid, CDS numbers CB17B_P047 to CB17B_P052. B. The published sequence of Group II C. botulinum type E strain Alaska E43 (accession number NC_010723) shows that the neurotoxin gene is located on the chromosome in an orfX cluster, CDS CLH_1110 to CLH_1115.