Characterization of adhesion between Limosilactobacillus reuteri and milk phospholipids by density gradient and gene expression

Abstract

Adhesion between lactic acid bacteria (LAB) and milk phospholipids may be correlated with positive effects on human health. We present a method to characterize and quantify potential adhesion between lactic acid bacteria and milk phospholipids with a physical test. The association between such adhesion and the expression of surface binding-promoting genes of Limosilactobacillus reuteri has been analyzed. Our results lead to a better understanding of the interaction between lactic acid bacteria and milk phospholipids and contribute to the development of fermented dairy products supplemented with milk phospholipids. Highlights • The interaction between lactic acid bacteria and milk phospholipids can be semi-quantified • Binding and interaction between milk phospholipids and LAB is mediated by gene modulation • Two of three genes for surface adhesion corresponded directly with binding results • This method identifies LAB that adhere tightly to the intestinal membranes Abstract: The benefits of fermented dairy products, in particular the presence of lactic acid bacteria (LAB) and milk phospholipids (MPL), seem to correlate with positive effects on human health. We hypothesize that one aspect of this benefit is the adhesion of LAB to the milk fat globule membrane via the interaction of LAB and MPL. Our first objective was to present a method to characterize and quantify such adhesion and investigate its association with a physical test. Our second objective was to further analyze the mechanism of interaction by analyzing expression of 3 previously reported surface binding-promoting genes (MapA, Cnb, and CmbA). We categorized adhesion between MPL and LAB by observing the distribution of MPL in corresponding bacterial cultures. Our working hypothesis was that any interaction or adhesion between these 2 components would yield differences in the distribution of MPL. Out of 122 LAB tested, 27% showed what could be characterized as adhesion; 38% of these strains were Limosilactobacillus reuteri. Further characterization of adhesion was carried out using an reverse transcription quantitative-PCR experiment, which demonstrated that the relative expression level of CmbA was positively associated with that adhesion. In addition, supplementation of MPL caused overexpression of MapA and Cnb in L. reuteri OSU-PECh-37A and OSU-PECh-48. This study indicated strain-specific adhesion between MPL and LAB and suggested that CmbA, which encodes a surface protein, is a potential factor involved in that adhesion. A better understanding of interactions between MPL and LAB may contribute to the design of new functional products and improve the delivery of these bioactive ingredients to their target site of action.