UNCOVERING THE EFFECTS OF ZINC AND CALCIUM ON INTERACTIONS BETWEEN MUCINS AND LACTOBACILLACEAE

Essential metals such as calcium, zinc, and iron are required for life. Essential metals serve various catalytic, regulatory, and signaling functions in the human body while also affecting the microbiota. The mucus layer of the gastrointestinal (GI) tract is a critical habitat for the microbiota, providing protection to the GI tract as well as adhesion sites to resident microorganisms and probiotics, which are live organisms that confer a health benefit when consumed in adequate amounts. Microbe-host adhesion interactions are important for probiotics to perform well. Mucin proteins, which comprise the mucus layer, can bind metal ions. In addition, the surface of some probiotics may have metal binding sites, including Ca2+-binding sites of Mucus Binding Protein from Lactobacillaceae reuteri 1063. We propose that these metals may also influence binding interactions between mucins and Lactobacillaceae. As probiotics, Lactobacillaceae also compete with pathogens to keep the human body healthy, and zinc is used in Zn2+-deficient individuals to treat E. coli-induced diarrhea. Studying the effects of essential metals in competitive adhesion of gut bacteria will provide insight to the molecular mechanisms behind physiological and pathological conditions in the GI tract. Lactobacillus acidophilus and Lactiplantibacillus plantarum are chosen for this work. Both species a from the Lactobacillaceae family that are considered to permanently colonize the intestinal tract. This work reveals that zinc and calcium ions present during mucin-Lactobacillaceae binding process affect Lactobacillaceae adhesion to mucins. In addition, we find that pH affects both mucin-Lactobacillaceae binding affinity and sensitivity to the influence of metal ions. We also describe how subculturing with metals or mucins affects the adhesion ability to mucins and sensitivity to metal ions for Lactobacillaceae. This work lays a foundation for studying the mechanisms underlying how metals affect Lactobacillaceae inhabiting the GI tract.