engleski

The Role of S-Layer Proteins in Probiotic Properties of Levilactobacillus brevis Strains Isolated from Human Milk Microbiota

Infant’s intestinal microbiome is believed to be highly influenced by their own mother’s breast milk microbiota. Mother’s milk is a rich source of nutrients, bioactive components, but also a diversity of microorganisms that are important for the health of a newborn. The focus of our research was screening of the Lactobacillus strains that rarely, but preferably, express S-proteins. Among over 100 strains, we have identified S-proteins solely in the 4 strains of Levilactobacillus spp. This is the first report that describes S-proteins of Levilactobacillus brevis strains isolated from mother’s milk. Four L. brevis strains, MB1, MB2, MB13 and MB20, were identified by whole genome sequencing. Gene annotation confirmed the presence of S-layer proteins, which were further identified by SDS-PAGE coupled to LC-MS/MS. The examined L. brevis strains possess S-proteins of 40-50 kDa. Further characterization revealed that S-proteins protect bacterial cells against adverse environmental stresses, such as those in gastrointestinal tract (GIT) or during freeze- drying, but also interact during cell adhesion to intestinal surfaces. This was observed through increased survival of the L. brevis strains in simulated GIT conditions, increased adhesion to Caco-2 cell line and stronger inhibition of adhesion of pathogenic bacterium Escherichia coli 3014 to Caco-2 cell line, as mentioned properties were negatively affected after the removal of S- layer proteins from the cell surface. Results imply that S-proteins mediate functional properties of the producer strains. Overall, S- layer proteins of investigated L. brevis strains have the potential to act as key mediators for their functionalities.

breast milk microbiota ; Levilactobacillus brevis ; S-proteins

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