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Uremic toxins (UTs) are microbiota-derived metabolites that accelerate the progression of kidney damage in patients with chronic kidney disease (CKD). One of the major UTs involved in CKD progression is p -cresol-sulfate (PCS), derived from dietary l-tyrosine (l-Tyr). Here, we engineered a probiotic strain of Escherichia coli Nissle 1917, to convert l-Tyr to the nontoxic compound p -coumaric acid via tyrosine ammonia lyase (TAL). First, a small metagenomic library was assessed to identify the TAL with the greatest whole-cell activity. Second, accessory genes implicated in the import of l-Tyr and export of PCA were overexpressed to enhance l-Tyr degradation by 106% and 56%, respectively. Last, random mutagenesis coupled to a novel selection and screening strategy was developed that identified a TAL variant with a 25% increase in whole-cell activity. Taken together, the final strain exhibits a 183% improvement over initial whole-cell activity and provides a promising candidate to degrade l-Tyr mediated PCS accumulation.

Gram-positive Staphylococcus aureus infection that results in pneumonia, urinary tract infection, and in severe cases, sepsis, has recently been classified as a serious threat to public health. Rapid and cost-effective detection of these infections are costly and time-consuming. Here, we present probiotic lactic acid bacteria engineered to detect autoinducer peptide-I (AIP-I), a quorum sensing molecule produced by Staphylococcus sp. during pathogenesis. We achieved this by adapting the well-characterized agr quorum sensing ( agrQS) from Staphylococcus aureus into Lactobacillus reuteri. The engineered biosensor is able to detect AIP-I levels in the nanomolar to micromolar range. We further investigated the function of the biosensor to detect real-time changes in AIP-I levels to understand the dynamics of Staphylococcus aureus under various strenuous conditions. The developed sensors would be useful for detection of Staphylococcus contamination in hospital settings and for high-throughput drug screening.