Engineered probiotic Lactobacillus plantarum WCSF I for monitoring and treatment of Staphylococcus aureus infection.

Lactobacillus plantarum is one of the most thoroughly researched species of the genus Lactobacillus , which possesses the characteristics of easy genetic transformation, high-density growth, and high intestinal tract survival. L. plantarum has been proven to play a potential role as a probiotic delivery vector. Staphylococcus aureus is a common Gram-positive pathogenic bacterium. It uses an autoinducer peptide (AIP) produced by its Agr quorum-sensing (AgrQS) system to sense the population density. Using the quorum-sensing mechanism exclusive to S. aureus , we constructed an AgrQS system in L. plantarum WCSF induction and killing modules based on AIP sensing and regulation so that L. plantarum could effectively eliminate S. aureus when detecting exogenous AIP at nanomolar concentrations. By optimizing the expression strength of the two-component system AgrAC using different L. plantarum -derived promoters and replacing the core promoter of the AgrA-activating promoter, the activation strength of AgrQS increased from the initial 1.2-fold to 5.3-fold. By introducing the signal peptide N20-guided lysostaphin aureus protein, engineered L. plantarum was able to effectively control the release of lysostaphin aureus protein and inhibit the growth of S. aureus . For the first time, engineered L. plantarum can detect and treat S. aureus infection, laying the groundwork for the future development of engineered probiotics for the monitoring and therapy of intestinal pathogens.IMPORTANCEBacterial infection and the emergence of drug-resistant strains are major problems in clinical treatment. Staphylococcus aureus , which typically infects the skin and blood of animals, is also a potential intestinal pathogen that needs to be addressed by the emergence of a new treatment approach. Probiotic therapy is the most likely alternative to antibiotic therapy to solve the problem of bacterial drug resistance in clinical practice. In this study, the engineered Lactobacillus plantarum can not only sense the signal AIP to detect S. aureus but also kill S. aureus by secreting the lysostaphin enzyme. Our strategy employed an Agr quorum-sensing genetic circuit to simultaneously detect and treat pathogenic bacteria, which provided a theoretical possibility for solving practical clinical bacterial infection cases in the future.