Proposal to reclassify the three biotypes as three subspecies: Bifidobacterium longum subsp. longum subsp. nov., Bifidobacterium longum subsp. infantis comb. nov. and Bifidobacterium longum subsp. suis comb. nov.

In the year 2002 Bifidobacterium longum, B. infantis and B. suis were unified into a single species, B. longum, preserving the former species names through the creation of the three biotypes ‘longum’, ‘infantis’ and ‘suis’. Consequently the use of the species name B. infantis and B. suis was to be discontinued. The above taxonomic rearrangement of B. longum was based on DNA-DNA hybridizations, 16S rRNA and HSP60 sequence analysis. However a variety of other genotypic techniques including ribotyping, ARDRA, RAPD-PCR, BOX-PCR, PCR-DGGE, comparison of the Rec A, tuf and ldh gene sequences, plasmid profiling and considerable variation in carbohydrate fermentation patterns as well as results of starch and PAGE electrophoresis experiments, clearly discriminate former ‘B. longum’, ‘B. infantis’, and ‘B. suis’ strains. In the present paper we compile this published information and propose the description of Bifidobacterium longum subsp. longum subsp. nov., Bifidobacterium longum subsp. infantis comb. nov. and Bifidobacterium longum subsp. suis comb. nov. The “International Committee on Systematic Bacteriology Subcommittee on Bifidobacterium, Lactobacillus and related organisms” is in favour of this proposal.