The effect of moonlighting proteins on the adhesion and aggregation ability of Lactobacillus helveticus

• Bacterial surface properties of Lactobacillus helveticus strains was examined.
• Analysis of adhesion and aggregation ability of tested strains was performed.
• Cellular proteins in L. helveticus strains were analyzed by the label-free method.
• Moonlighting proteins were identified that are involved in adhesion mechanism.

The goal of this study was to identify moonlighting proteins in Lactobacillus helveticus that play an important role in adhesion and aggregation. The label-free method was used for identification and analysis of expression of cellular proteins. The analysis revealed the presence of eight moonlighting proteins in the cell envelope of Lb. helveticus. The tested strains mainly differed with respect to the presence of S-layer proteins and the level of expression of moonlighting proteins in Lb. helveticus strain T159. These surface proteins give the cell a hydrophobic character and play a role in specific interactions with intestinal epithelium cells and with other bacteria. In Lb. helveticus T159, the S-layer associated with moonlighting proteins could act as adherence factors, which was evidenced by the high capability of adhesion, auto- and coaggregation. The hydrophobicity, adhesion and aggregation abilities provide biological activities in food products and they are regarded as an important criterion for probiotic selection.