University of Wisconsin–Madison

Probiotic-Host Interactions

Probiotic bacteria are defined as “live micro-organisms, which when administered in adequate amounts, confer a health-benefit to the host”. Despite the fact that probiotic bacteria are exploited in foods and medicine, we know relatively little about the mechanisms by which these health-promoting bacteria elicit their effects.

One of the goals of the van Pijkeren Laboratory is to unravel the functional mechanisms driving probiotic function. We are working to understand how strains of lactic acid bacteria activate the aryl-hydrocarbon receptor (Ahr). Ahr is a ligand-activated transcriptional regulator that plays a key role in maintaining gut homeostasis. In addition, activation of Ahr has been shown to have a protective effect in the development of colitis and colon cancer.

We tested an extensive library of lactic acid bacteria strains for their ability to activate Ahr, using a high-throughput cell-culture screen. We identified a small number of strains that strongly activate Ahr in a reproducible and robust manner. Comparative genomics then revealed candidate genes that may be responsible for the Ahr-activating genotype, which we are currently investigating through gene inactivation studies.

A key implication of this work is that, by understanding the mechanism by which select strains modulate the immune-system, we are in a unique position to edit food-grade bacteria to further enhance their health-promoting properties.