In vitro fermentation of breast milk oligosaccharides by Bifidobacterium infantis and Lactobacillus gasseri

In vitro fermentability of human milk oligosaccharides by several strains of bifidobacteria

This study was conducted to investigate the catabolism and fermentation of human milk oligosaccharides (HMO) by individual strains of bifidobacteria. Oligosaccharides were isolated from a pooled sample of human milk using solid-phase extraction, and then added to a growth medium as the sole source of fermentable carbohydrate. Of five strains of bifidobacteria tested (Bifidobacterium longum biovar infantis, Bifidobacterium bifidum, Bifidobacterium longum biovar longum, Bifidobacterium breve, and Bifidobacterium adolescentis), B. longum bv. infantis grew better, achieving triple the cell density then the other strains. B. bifidum did not reach a high cell density, yet generated free sialic acid, fucose and N-acetylglucosamine in the media, suggesting some capacity for HMO degradation. Thin layer chromatography profiles of spent fermentation broth suggests substantial degradation of oligosaccharides by B. longum bv. infantis, moderate degradation by B. bifidum and little degradation by other strains. While all strains were able to individually ferment two monosaccharide constituents of HMO, glucose and galactose, only B. longum bv. infantis and B. breve were able to ferment glucosamine, fucose and sialic acid. These results suggest that as a potential prebiotic, HMO may selectively promote the growth of certain bifidobacteria strains, and their catabolism may result in free monosaccharides in the colonic lumen.

From bacterial genome to functionality; case bifidobacteria

The availability of complete bacterial genome sequences has significantly furthered our understanding of the genetics, physiology and biochemistry of the microorganisms in question, particularly those that have commercially important applications. Bifidobacteria are among such microorganisms, as they constitute mammalian commensals of biotechnological significance due to their perceived role in maintaining a balanced gastrointestinal (GIT) microflora. Bifidobacteria are therefore frequently used as health-promoting or probiotic components in functional food products. A fundamental understanding of the metabolic activities employed by these commensal bacteria, in particular their capability to utilize a wide range of complex oligosaccharides, can reveal ways to provide in vivo growth advantages relative to other competing gut bacteria or pathogens. Furthermore, an in depth analysis of adaptive responses to nutritional or environmental stresses may provide methodologies to retain viability and improve functionality during commercial preparation, storage and delivery of the probiotic organism.

Glycoprofiling of bifidobacterial consumption of human milk oligosaccharides demonstrates strain specific, preferential consumption of small chain glycans secreted in early human lactation

The molecular basis by which human breast milk supports the development of a protective intestinal microbiome in infants is unknown. After lactose and lipids, human milk oligosaccharides (HMOs) are quantitatively the third largest and most diverse component of breast milk. In this work, glycomic profiling of HMO consumption by bifidobacteria using Fourier transform ion cyclotron resonance mass spectrometry reveals that one species, Bifidobacterium longum biovar infantis ATCC 15697, an isolate from the infant gut, preferentially consumes small mass oligosaccharides, representing 63.9% of the total HMOs available. These HMOs were detected in human breast milk at the onset and constantly through the first month of lactation by use of high performance liquid chromatography-chip time-of-flight mass spectrometry. Further characterization revealed that strain ATCC 15697 possesses both fucosidase and sialidase activities not present in the other tested strains. This work provides evidence that these small mass HMOs are selectively metabolized by select bifidobacterial strains and represent a potential new class of bioactive molecules functioning as prebiotics to facilitate a protective gut colonization in breast-fed newborns.

Genomics of Actinobacteria: tracing the evolutionary history of an ancient phylum

Actinobacteria constitute one of the largest phyla among bacteria and represent gram-positive bacteria with a high G+C content in their DNA. This bacterial group includes microorganisms exhibiting a wide spectrum of morphologies, from coccoid to fragmenting hyphal forms, as well as possessing highly variable physiological and metabolic properties. Furthermore, Actinobacteria members have adopted different lifestyles, and can be pathogens (e.g., Corynebacterium, Mycobacterium, Nocardia, Tropheryma, and Propionibacterium), soil inhabitants (Streptomyces), plant commensals (Leifsonia), or gastrointestinal commensals (Bifidobacterium). The divergence of Actinobacteria from other bacteria is ancient, making it impossible to identify the phylogenetically closest bacterial group to Actinobacteria. Genome sequence analysis has revolutionized every aspect of bacterial biology by enhancing the understanding of the genetics, physiology, and evolutionary development of bacteria. Various actinobacterial genomes have been sequenced, revealing a wide genomic heterogeneity probably as a reflection of their biodiversity. This review provides an account of the recent explosion of actinobacterial genomics data and an attempt to place this in a biological and evolutionary context.

Variation of major neutral oligosaccharides levels in human colostrum

OBJECTIVES

Human colostrum is known to be important for the protection of infants against infection by pathogenic microorganisms. This protection is thought to be due, partially, to various neutral and acidic oligosaccharides that are present in colostrum and milk. However, the concentrations of each of the oligosaccharide of human colostrum have not yet been determined. The aim of this present study was to determine the concentration of each of the major neutral oligosaccharide for three consecutive days from the start of lactation.

METHOD

We analyzed the level of each neutral oligosaccharide in human colostrum, for three consecutive days from the start of lactation, obtained from 12 healthy Japanese women (ranging in age from 21 to 35 years; primipara 6 and multipara 6). The ABO blood groups of the donors were determined: A, three; B, three; O, five; AB, one. The determined human milk oligosaccharides were 2'-fucosyllactose (2'-FL), 3-fucosyllactose (3-FL), lactodifucotetraose (LDFT), lacto-N-tetraose (LNT), lacto-N-neotetraose (LNnT), three lacto-N-fucopentaose (LNFP I, II and III) and two lacto-N-difucohexaose (LNFDH I and II) using high-performance liquid chromatography (HPLC) with two derivatization techniques.

RESULTS

The concentrations of 2'-FL and LDFT in colostrum on day 1 were significantly higher than those on days 2 and 3 (P<0.05). An increase in LNT was observed on day 3 compared with day 1 (P<0.05).

CONCLUSION

These changes in concentrations of 2'-FL, LDFT and LNT may reflect the requirements for prebiotics and anti-infection agents by human infants during early lactation.

Neutral oligosaccharides in colostrum in relation to maternal allergy and allergy development in children up to 18 months of age

Several recent studies have demonstrated a relationship between the composition of the gut microbiota in infancy and subsequent development of allergic disease. Human milk is the major food in infancy and may thus profoundly influence the composition of the gut flora. Oligosaccharides in breast milk survive the passage through the stomach and are utilized by the gut microbiota. As the relationship between breast feeding and childhood allergy is controversial we hypothesized that the composition of oligosaccharides in breast milk might explain the controversy. Nine of the most abundant neutral oligosaccharides in human milk were analysed in colostrum samples from allergic and non-allergic women and related to subsequent development of allergy in their children. The carbohydrate fraction of the colostrum was separated by gel permeation chromatography and neutral oligosaccharides, tri- to hexasaccharides were collected. Neutral oligosaccharides were analysed with high-performance liquid chromatography. There was a large variation in the concentration of neutral oligosaccharides in colostrum, which could not be explained by the allergic status of the women. Allergic children consumed higher amounts of neutral oligosaccharides in total, although not significantly (p = 0.12). When different oligosaccharides were analysed separately, there was no significant difference in consumption between the infants who developed atopic allergy later (n = 9) and infants who did not (n = 11). Thus, the amount of neutral oligosaccharides in colostrum does not directly correlate with maternal allergy, nor with allergy development in children up to 18 months of age.

Methods for the quantitation of human milk oligosaccharides in bacterial fermentation by mass spectrometry

Oligosaccharides are the third most abundant component in human milk. In the past decades, it became apparent that they would be able to protect against pathogens and participate in the development of the gut microflora for infants. However, their role in infants' nutrition and development remains poorly understood. To better understand this function, it is extremely important to have a quantitative tool for profiling oligosaccharides. In this article, we show the development of a method to quantitatively differentiate the relative amounts of oligosaccharides fermented by different intestinal bacteria. To determine the oligosaccharide consumption, bacteria were grown in a medium using human milk oligosaccharides (HMOs) as the only carbon source purified from breast milk and further analyzed by matrix-assisted laser desorption/ionization-Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICR MS). A method using an internal deuterium-labeled standard was developed and compared with an external standard method, with the internal standard method giving better precision and unambiguous measurements than the external standard method and providing to be a novel and robust tool for following bacterial fermentation of milk oligosaccharides.

Genomics as a means to understand bacterial phylogeny and ecological adaptation: the case of bifidobacteria

The field of microbiology has in recent years been transformed by the ever increasing number of publicly available whole-genome sequences. This sequence information has significantly enhanced our understanding of the physiology, genetics and evolutionary development of bacteria. Among the latter group of microorganisms, bifidobacteria represent important human commensals because of their perceived contribution to maintaining a balanced gastrointestinal tract microbiota. In recent years bifidobacteria have drawn much scientific attention because of their use as live bacteria in numerous food preparations with various health-related claims. For this reason, these bacteria constitute a growing area of interest with respect to genomics, molecular biology and genetics. Recent genome sequencing of a number of bifidobacterial species has allowed access to the complete genetic make-up of these bacteria. In this review we will discuss how genomic data has allowed us to understand bifidobacterial evolution, while also revealing genetic functions that explains their presence in the particular ecological environment of the gastrointestinal tract.