Development of a nitrate-responsive whole-cell biosensor based on engineered probiotic Saccharomyces boulardii

Area of Science:

• Microbiology
• Synthetic Biology
• Biotechnology

Background:

• Nitrate is a biomarker for gut inflammation.
• Probiotic yeasts like Saccharomyces boulardii offer potential for therapeutic applications.
• Genetic engineering enables the development of novel biosensing tools.

Purpose of the Study:

• To construct a nitrate-responsive biosensor using the probiotic yeast Saccharomyces boulardii.
• To engineer a genetic circuit for nitrate detection in a host lacking native nitrate assimilation pathways.

Main Methods:

• Introduction of nitrate assimilation pathway genes (YNT1, YNA1, YNA2) from Ogataea polymorpha into Saccharomyces boulardii.
• Utilized CRISPR/Cas9 genome editing to create the engineered strain SKSC499.
• Evaluated promoter activity (YNT1, YNI1, YNR1) driving a reporter gene in response to nitrate.

Main Results:

• Successfully engineered Saccharomyces boulardii (strain SKSC499) with a functional nitrate-sensing genetic circuit.
• The YNR1 promoter demonstrated nitrate-dependent induction of reporter gene expression.
• The biosensor exhibited growth in the presence of nitrate and the antibiotic G418.

Conclusions:

• A novel Saccharomyces boulardii-based biosensor capable of detecting nitrate has been successfully developed.
• This engineered probiotic yeast holds promise for monitoring gut inflammation biomarkers.
• The study showcases the potential of synthetic biology for creating targeted microbial therapeutics.