Electronic Thesis and Dissertation Repository


Master of Science


Microbiology and Immunology


Dr. Gregor Reid


Toxic metals are a class of elements with no biological role but with extreme toxicity. On average only 50% of ingested toxins are absorbed into the human body, for reasons still unknown. It was hypothesized that the gut microbiota plays a role in reducing toxin absorbance. The aim of this study was to determine if constituents of the gut, namely Lactobacillus species, are able to sequester arsenic, lead and cadmium from the environment. Lactobacilli were incubated with the metals, both in vitro and with a Caco-2 cell line. Analysis of metal concentrations was conducted to determine if these were reduced by lactobacilli and if this in turn lowered mortality of the Caco-2 cells, and to establish if lactobacilli could block transport of metals across a cell layer. In vitro studies and electron microscopy showed that lactobacilli had significant binding potential to the metals lead and cadmium. In addition, they conferred protection of Caco-2 cells from toxicity with less metal binding to the epithelial cell surfaces. This supports my hypothesis and raises the concept of using probiotic lactobacilli, perhaps in a food formulation, to reduce heavy metal exposure and poisoning. A yogurt formulation was created using two strains with metal-binding potential, and this could be tested in the future.