A Quorum-Sensing-Based Genetic Circuit for Bioengineered Bacterial Treatment of Bovine Mastitis

Bovine mastitis is a significant challenge for the dairy industry, affecting milk production, quality, and cow health. Traditional antibiotic-based treatments raise concerns about resistance and residual antibiotics in dairy products, creating an urgent need for sustainable alternatives. This study explores a genetically modified organism (GMO)-based, antibiotic-free treatment targeting Staphylococcus aureus, a primary mastitis-causing pathogen. This study proposes using the bioengineered defensin Nisin PV, which has enhanced stability and reduced susceptibility to proteolytic degradation compared to Nisin A. This makes it a more effective, pathogen-specific alternative to broad spectrum antibiotics, reducing off-target effects and supporting responsible antimicrobial stewardship. To disrupt biofilm formation, this study utilizes deoxyribonuclease I (DNase I), an enzyme that degrades extracellular deoxyribonucleic acid (DNA), a key structural biofilm component. This genetically modified bacteria detects S. aureus through its agr quorum sensing system and responds by producing Nisin PV and DNase I. Experimental results confirm DNase I’s efficacy asgainst biofilm formation and validate this quorum sensing-based pathogen detection mechanism. Molecular dynamics simulations further suggest that Nisin PV resists cleavage by bacterial strains resistant to Nisin A. A regulated lysis mechanism is proposed to ensure controlled therapeutic release. This study highlights the potential of bioengineered defensins as an effective, sustainable alternative to antibiotics, offering a promising strategy to reduce mastitis incidence and economic losses in the dairy industry.