Effects of metals on probiotic Lactobacillus



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The gastrointestinal tract (GIT) contains trillions of microorganisms with over 1000 bacterial species, including probiotic bacteria. Probiotics are live microorganisms with positive effects on the host if administered in sufficient amounts. Gut microbes, including [HU1] probiotic species, help build the immune system, protect against pathogens, and synthesize nutrients. The abundance of gut microbes can be affected by changes such as diet, antibiotics, diseases, or infection. Lactobacilli are mostly found in the small intestine and used in probiotic formulations. Intestinal Lactobacillus species can be affected by changes in dietary essential metals, including calcium and zinc. Many Lactobacilli can form biofilm to colonize the GIT, subsequently promoting human health and effectiveness of probiotics. However, there are few studies on the metal effects on their biofilm formation. Here, we focused on the effect of zinc and calcium on biofilm formation of L. plantarum and L. acidophilus which have known mucus-binding domains that can facilitate biofilm formation and possibly, metal-binding. L. acidophilus has the S-layer proteins and L. plantarum have mannose-binding properties that can help them adhere to the GIT and aggregate to form biofilm. To determine the extent to which metals can affect biofilm formation, we examined their biofilm formation under varied metal concentrations using crystal violet (CV) and colony-forming unit (CFU) count assays. We detected an increase in biofilm formation when the biofilm was grown under increasing zinc and calcium concentration. Zinc promotes the viability of both Lactobacillus species, while calcium induced their biofilm to grow faster, especially to L. acidophilus.