Minority species influences microbiota formation: the role of Bifidobacterium with extracellular glycosidases in bifidus flora formation in breastfed infant guts.
Gotoh A, Ojima MN, Katayama T
Microb Biotechnol. Jan 2019. doi: 10.1111/1751-7915.13366
COMMENT: The article highlights the importance of rare Bifidobacterium longum strains with extracellular glycosidases as keystone species in the formation of the bifidus flora in breastfed infants.
Some recent studies have reported instances where certain minority species play a critical role in creating locally stable conditions for other species by stabilizing the fundamental microbiota, despite their low abundance. These minority species act as ‘keystone species
In this paper, we propose that more emphasis should be placed on minority taxa and their possible role as keystone species in gut microbiota studies by referring to our recent studies on HMO-mediated (human milk oligosaccharides mediated) microbiota formation in the infant gut. (...) it is highly likely that HMOs serve as selective nutrients for bifidobacterial species.
In the infant gut, the most abundant genus is generally Bifidobacterium, and the carbon source that is the most available to them comes from HMOs in breast milk. Interestingly, the four infant gut-associated bifidobacterial species and their multiple strains have evolved different strategies to degrade HMOs and to maintain diversity. We demonstrated that B. longum strains that express lnbX (extracellular enzyme lacto-N-biosidase) and B. bifidum are potential keystone species in the establishment of the bifidus flora by providing HMO degradants for other bacterial groups to use. In other words, the cross-feeding between minority taxa and dominant taxa is an important mechanism for the formation and maintenance of a diverse bifidus flora