The role of structure in the interaction between bacteria, mammary epithelial cells and milk fat globules from raw or “cultured” milk

The study aimed to distinguish between the role played by the structural properties of MFG from its chemical composition in modulating its interaction with pathogenic and commensal bacteria. MFG from mammary gland epithelial cells (MEC) or raw milk was tested. Small MFG from both sources promoted growth of B.subtilis while large MFG triggered biofilm formation. Metabolomic profiles supported these findings for MEC-derived MFG. In contrast, pathogenic bacteria like E. coli weren't affected by MFG size from both sources. Using lipid mixture formulated to mimic the chemical composition of small MFG did not induce growth of the bacteria. Results validate that (i) milk components secreted by MEC share some structural-functional properties with raw MFG and (ii) the structure of the MFG plays a pivotal role in modulating the interaction between milk fat and bacteria. Taken together, MFG size variations may provide a competitive advantage to commensal bacteria as a protective mechanism.