The place of Listeria among gram-positive bacteria.

The genus Listeria, containing the species Listeria monocytogenes, Listeria innocua, Listeria seeligeri, Listeria welshimeri, Listeria ivanovii, Listeria grayi and Listeria murrayi is a well circumscribed taxon. Numerical taxonomic and chemical studies indicate a very close phenetic similarity to the genus Brochothrix and a more distant, but close, similarity to a number of other genera such as Lactobacillus, Streptococcus, Lactococcus, Enterococcus, Staphylococcus, Kurthia and Bacillus. Recent 16S rRNA oligonucleotide studies have not only confirmed this relatedness but have provided information that has allowed the construction of a tentative phylogenetic classification of these taxa. On this classification the genus Listeria is very close to Brochothrix and both genera occupy a position between Lactobacillus and Bacillus.