Genomic sequences of six botulinum neurotoxin-producing strains representing three clostridial species illustrate the mobility and diversity of botulinum neurotoxin genes

Abstract The whole genomes for six botulinum neurotoxin-producing clostridial strains were sequenced to provide references for under-represented toxin types, bivalent strains or unusual toxin complexes associated with a bont gene. The strains include three Clostridium botulinum Group I strains (CDC 297, CDC 1436, and Prevot 594), a Group II C. botulinum strain (Eklund 202F), a Group IV Clostridium argentinense strain (CDC 2741), and a Group V Clostridium baratii strain (Sullivan). Comparisons of the Group I genomic sequences revealed close relationships and conservation of toxin gene locations with previously published Group I C. botulinum genomes. The bont /F6 gene of strain Eklund 202F was determined to be a chimeric toxin gene composed of bont /F1 and bont /F2. The serotype G strain CDC 2741 remained unfinished in 20 contigs with the bont /G located within a 1.15 Mb contig, indicating a possible chromosomal location for this toxin gene. Within the genome of C. baratii Sullivan strain, direct repeats of IS1182 insertion sequence (IS) elements were identified flanking the bont /F7 toxin complex that may be the mechanism of bont insertion into C. baratii . Highlights of the six strains are described and release of their genomic sequences will allow further study of unusual neurotoxin-producing clostridial strains.