Long before 16S rRNA profiles were applied to define microbial phylogenies,
the genus Clostridium was defined as containing Gram positive,
obligate or strictly anaerobic non-sulphate reducing bacteria
(Hippe et al., 1992). It is now apparent that the traditionally classified
genus Clostridium is very heterogeneous and contains over 100 species,
leading to it being divided into distinct clusters based on 16S rRNA gene
homology by Collins in 1994 (Collins et al., 1994).