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Bifidobacterium longum subsp. infantis
Bifidobacterium longum subsp. infantis (ex B. infantis) is a Gram-positive, anaerobic catalase- and oxidase-negative, non-motile, non-spore-forming, irregularly shaped rod microorganism. It has been isolated from infant feces and firstly named B. infantis by Reuter in 1963. Due to its high DNA-DNA homology with B. longum and B. suis it has been unified with these species and renamed B. longum subsp. infantis (Mattarelli et al., 2008). This species together with B. breve is typically found in human infant gastrointestinal tract. The presence of Bifidobacteriaceae members in infant gut can reach 90% of the total gut microbiota. One interesting theory is that human milk oligosaccharides (HMOs) do not nourish the infant directly, instead they are considered growth factors that direct select bacterial communities in the GIT. B. longum subsp. infantis and B. breve share the common feature of selectively utilizing HMO, and the genome, sequenced for B. longum subsp. infantis, reveals the presence of more genes associated with oligosaccharide transport than in species typical of adults such as B. adolescentis. Many studies underlines the importance of B. longum subsp. infantis and other bifidobacteria in shaping immunological system together with other beneficial characteristics such as antagonist activity towards pathogens, vitamin production and anticarcinogenic activity. This species has a long history of safe use as probiotic adjunct in foods and in pharmaceutical preparations and for this reason it has been recognized as GRAS and QPS as almost all the species belonging to Bifidobacterium genus.
Mattarelli P., Bonaparte C., Pot B., Biavati B. (2008). 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. Int. J. Syst. Evol. Microbiol. 58: 767 - 772.