Evolution of Chromosomal Clostridium botulinum Type E Neurotoxin Gene Clusters: Evidence Provided by Their Rare Plasmid-Borne Counterparts.

ABSTRACT: Analysis of more than 150 Clostridium botulinum Group II type E genomes identified a small fraction (6%) where neurotoxin-encoding genes were located on plasmids. Seven closely related (134-144 kb) neurotoxigenic plasmids of subtypes E1, E3, and E10 were characterized; all carried genes associated with plasmid mobility via conjugation. Each plasmid contained the same 24-kb neurotoxin cluster cassette (six neurotoxin cluster and six flanking genes) that had split a helicase gene, rather than the more common chromosomal rarA. The neurotoxin cluster cassettes had evolved as separate genetic units which had either exited their chromosomal rarA locus in a series of parallel events, inserting into the plasmid-borne helicase gene, or vice versa. A single intact version of the helicase gene was di

SUBMITTER: Carter AT 

PROVIDER: S-EPMC4824171 | biostudies-literature | 2016 Mar

REPOSITORIES: biostudies-literature