| Bifidobacteriaceae | |
|---|---|
 | |
| Bifidobacterium adolescentis | |
Scientific classification | |
| Domain: | Bacteria |
| Kingdom: | Bacillati |
| Phylum: | Actinomycetota |
| Class: | Actinomycetes |
| Order: | Bifidobacteriales Stackebrandtet al. 1997[1] |
| Family: | Bifidobacteriaceae Stackebrandtet al. 1997[1] |
| Type genus | |
| Bifidobacterium Orla-Jensen 1924 (Approved Lists 1980) | |
| Genera[2] | |
| |
TheBifidobacteriaceae are the onlyfamily ofbacteria in theorderBifidobacteriales.[3]
The familyBifidobacteriaceae stain [Gram-positive], range from obligate to faculatively anaerobic, are non-motile, non-filamentous and non-spore forming.[4] Their morphology is varied and ranges from Y- or V-shaped (from which the bifidobacteria derived their name) to ones with enlarged or flattened ends (club- or spatula-shaped).[5] The branching nature ofBifidobacteria can change with different starins and media.[6] These rods appear as a solitary bacilli or as aggregates in chains or in clumps.[4]
Thesechemoorganotrophic microorganisms aresaccharolytic acid producers and do not produce gas.[4]
The Bifidobacteriaceae family is divided into ten genera (Bifidobacterium,Aeriscardovia,Alloscardovia,Bombiscardovia,Galliscardovia,Gardnerella,Neoscardovia,Parascardovia,Pseudoscardovia, andScardovia,[7] with three candidate generaCandidatus Ancillula,Candidatus Opitulatrix, andCandidatus Servula.[8]
AllBifidobacteraceae contain a peculiar metabolic pathway to catabolise six-carbon sugars (hexoses) involving the key enzymeFructose-6-phosphate phosphoketolase (EC 4.1.2.2), known as the fructose-6-phosphate pathway or the 'bifid shunt'.[4]
Comparative analysis of aligned protein sequences has led to the discovery of twoconserved signature indels which are specific for the orderBifidobacteriales. The firstindel, a 1amino acid deletion inribosomal protein L13, is found in allBifidobacteriales species and no otherActinomycetota, providing a potentialmolecular marker for the entireBifidobacteriales order. The second indel that has been identified is a 1 amino acid insertion inglucose-6-phosphate dehydrogenase found in allBifidobacterium species andG. vaginalis, but not in any otherActinomycetota. This indel is thus characteristic of theclade consisting ofBifidobacterium species andG. vaginalis and can be used to distinguish these genera from the rest of the orderBifidobacteriales. 16 conserved signature proteins have also been identified which are unique to the orderBifidobacteriales and can be used as molecular markers for this order. Additionally, 6 conserved signature proteins which are unique toBifidobacterium andGardnerella have been identified, providing further evidence that species from these two genera are closely related and providing molecular markers for the clade consisting of these genera.[9]
The currently accepted taxonomy is based on theList of Prokaryotic names with Standing in Nomenclature (LPSN).[2] The phylogeny is based on whole-genome analysis.[10]
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