Phenotypes
The current nomenclature for C. botulinum recognises four physiological groups (I-IV). The classification is based on the ability of the organism to digest complex proteins. Studies at the DNA and rRNA level support the subdivision of the species into groups I-IV. Most outbreaks of human botulism are caused by group I (proteolytic) or II (non-proteolytic) C. botulinum. Group III organisms mainly cause diseases in animals. There has been no record of Group IV C. botulinum causing human or animal disease.
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