# Evidence for the influence of the milk fat globule membrane on bifidobacteria metabolism and cell surface properties

## TL;DR

This study shows how milk fat globule membrane affects Bifidobacterium metabolism and cell properties, potentially enhancing its health benefits.

## Contribution

The study provides new evidence that milk fat globule membrane alters Bifidobacterium metabolism and cell surface characteristics.

## Key findings

- MFGM alters protein expression in B. infantis.
- Exopolysaccharide production increases with MFGM.
- MFGM thickens cell surface morphology and reduces surface charge.

## Abstract

Summary:Bifidobacterium longum ssp. infantis (B. infantis) is characteristic of a healthy breastfed infant microbiome that uses breast milk components to exert its beneficial effects on the host. Bifidobacterium longum ssp. infantis ATCC 15697 was grown in de Man, Rogosa, and Sharpe medium with 0.05% cysteine (MRSC) supplemented with either milk phospholipids (MPL) or digested infant formula containing milk fat globule membrane (MFGM). Samples of bacterial pellets and supernatants were collected during the exponential phase of growth when metabolism is highest. The bacterial cell metabolism was analyzed with proteomics, along with microscope imaging and cell surface charge evaluation. The bacterial supernatant was analyzed for exopolysaccharide production. Metabolism of B. infantis was altered in the presence of MFGM, where the protein expression was influenced, cell surface morphology was thicker and accompanied by a decrease in surface charge, and exopolysaccharide production increased. These results indicate MPL components may enhance the metabolism of B. infantis for increased host benefits.

Summary:Bifidobacterium longum ssp. infantis (B. infantis) is characteristic of a healthy breastfed infant microbiome that uses breast milk components to exert its beneficial effects on the host. Bifidobacterium longum ssp. infantis ATCC 15697 was grown in de Man, Rogosa, and Sharpe medium with 0.05% cysteine (MRSC) supplemented with either milk phospholipids (MPL) or digested infant formula containing milk fat globule membrane (MFGM). Samples of bacterial pellets and supernatants were collected during the exponential phase of growth when metabolism is highest. The bacterial cell metabolism was analyzed with proteomics, along with microscope imaging and cell surface charge evaluation. The bacterial supernatant was analyzed for exopolysaccharide production. Metabolism of B. infantis was altered in the presence of MFGM, where the protein expression was influenced, cell surface morphology was thicker and accompanied by a decrease in surface charge, and exopolysaccharide production increased. These results indicate MPL components may enhance the metabolism of B. infantis for increased host benefits.

•The MFGM affects the protein expression of B. infantis.•B. infantis increases secretion of extracellular polysaccharides with digested milk.•B. infantis cell surface charge is decreased with MPL.•MPL interact with and thicken the surface morphology of B. infantis.•B. infantis metabolic physiology changes in response to MFGM.

The MFGM affects the protein expression of B. infantis.

B. infantis increases secretion of extracellular polysaccharides with digested milk.

B. infantis cell surface charge is decreased with MPL.

MPL interact with and thicken the surface morphology of B. infantis.

B. infantis metabolic physiology changes in response to MFGM.

Bifidobacterium, a genus commonly found in the microbiome of healthy infants, has been demonstrated to exert various beneficial effects on the gastrointestinal tract, contributing to overall health. Notably, these bacteria possess the ability to use complex glycoconjugates as nutrients, which holds importance for breast-fed infants, as human milk contains substantial quantities of these glycoconjugates. However, the underlying mechanisms of action of these beneficial properties remain largely unexplored. This study presents an alternative perspective on the nutrients in the diet that could potentially support the maintenance of a healthy Bifidobacterium population. We present evidence suggesting that the presence of milk fat globule membrane (MFGM), a component shared by all mammalian milk, significantly alters the metabolism of these bacteria. This alteration is reflected in the production of exopolysaccharides on the surface and secretome of the bacteria fed MFGM, whereas the absence of this component does not result in such changes. To substantiate this hypothesis, we employed proteomic and physicochemical methods, culminating in the evidence of the MFGM layer through electron microscopy.