Deoxyribonucleic acid homology among the species of the genus Bifidobacterium isolated from animals

The Type Strain of Bifidobacterium indicum Scardovi and Trovatelli 1969 (Approved Lists 1980) is ATCC 25912, not DSM 20214, and Rejection to Reclassify Bifidobacterium coryneforme as Bifidobacterium indicum

In 2018, Nouioui et al. proposed that Bifidobacterium coryneforme was a later synonym of Bifidobacterium indicum on the basis of the digital DNA-DNA hybridization (dDDH) value (85.0%) between B. coryneforme LMG 18911T and B. indicum LMG 11587T. However, in the study of Scardovi et al. (1970), the type strains of B. indicum and B. coryneforme only exhibited 60% DNA-DNA hybridization value. In the present study, the genomes of B. coryneforme CGMCC 1.2279T, B. coryneforme JCM 5819T, B. indicum JCM 1302T, B. indicum CGMCC 1.2275T, B. indicum DSM 20214T, B. indicum LMG 27437T, B. indicum ATCC 25912T, B. indicum KCTC 3230T, B. indicum CCUG 34985T, were sequenced, and the taxonomic relationship between B. coryneforme and B. indicum was re-evaluated. On the basis of the results presented here, (i) ATCC 25912 and DSM 20214 deposited by Vittorio Scardovi are two different strains; (ii) the type strain of B. indicum is ATCC 25912T (= JCM 1302T = LMG 27437T = CGMCC 1.2275T = KCTC 3230T), and not DSM 20214 (= BCRC 14674 = CCUG 34985 = LMG 11587); (iii) B. coryneforme and B. indicum represent two different species of the genus Bifidobacterium; (iv) strain DSM 20214 (= BCRC 14674 = CCUG 34985 = LMG 11587) belongs to B. coryneforme.

Bifidobacterium population analysis in the infant gut by direct mapping of genomic hybridization patterns: potential for monitoring temporal development and effects of dietary regimens

A bifidobacterial mixed-species microarray platform was used in a proof-of-principle study to address the composition and development of bifidobacteria in DNA extracted from faecal samples. These were collected in a time-course of 2 years since birth and derived from human infants that were breastfed, standard formula-fed or received a prebiotic formula during their weaning period. A set of over 50 samples was analysed, testifying for the throughput of the designed platform for multiple genome hybridizations. The generated data revealed that faecal samples of breastfed infants contained a high abundance of genomic DNA homologous to Bifidobacterium breve. In contrast, faecal samples from standard formula-fed infants lacked detectable amounts of this B. breve DNA but contained genes with high similarity to B. longum. Remarkably, infants that received breastmilk and later a prebiotic formula consisting of a standard formula milk containing a mixture of specific galacto- and fructo-oligosaccharides, continued to harbour a B. breve-dominant faecal population. One infant that received standard formula in combination with the additional B. lactis Bb12 culture, contained significant amounts of faecal DNA belonging to Bb12 but only during the period of ingestion. The microarray platform showed sufficient sensitivity to analyse the B. breve group at the strain level. Overall, the B. breve populations observed in the faecal samples of the studied infants showed a stable composition over time and were unique per infant. In conclusion, our results show the applicability of comparative genome hybridization to study bifidobacterial populations in infant faecal samples without the use of any amplification step.

Genomic diversity and relatedness of bifidobacteria isolated from a porcine cecum

This study initially involved the isolation of a number of bifidobacteria from either the lumen or the epithelium of a porcine cecum. A total of 160 isolates were selected at random on MRS plates containing cysteine hydrochloride (0.5 g/liter) and mupirocin (50 mg/liter). All were identified as bifidobacteria based on fructose-6-phosphate phosphoketolase activity. Following genomic digestion with the restriction enzyme XbaI and pulsed-field gel electrophoresis (PFGE), the isolates produced 15 distinct macro-restriction patterns. Several of the PFGE patterns differed by only 1, 2, or 3 DNA fragments and were grouped as related patterns into seven PFGE types, termed A through G. The related patterns appeared to show genomic plasticity within the isolates arising from chromosomal mutations or possibly horizontal transfer of plasmids. The relative frequency of each PFGE type was maintained within each cecal sample, with PFGE type E representing approximately 50% of the isolates. Randomly amplified polymorphic DNA PCR, cell morphology, whole-cell protein profiling, 16S ribosomal DNA sequencing, and DNA-DNA hybridization were used to determine if the seven apparently unrelated PFGE types represented genetically distinct isolates. Four groups were identified: PFGE types A, C/D/G, B/E, and F, and these appeared to represent Bifidobacterium minimum, Bifidobacterium pseudolongum subsp. pseudolongum, and Bifidobacterium pseudolongum subsp. globosum and two new species, respectively. The data demonstrate the presence of considerable genomic diversity within a relatively simple bifidobacteria population, consisting of 15 distinct strains representing four groups, which was maintained throughout the porcine cecal contents and epithelial layer.

Biology of the bifidobacteria

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