Bacterial Fluorescence-Based Biosensor for Detecting Propionate in Culture Media for Diagnostic Applications

Area of Science:

• Synthetic biology applications in medical diagnostics.
• Bacterial engineering for metabolite detection.

Background:

• Engineering bacteria for disease diagnosis and treatment is an emerging field.
• Detecting short-lived molecules like short-chain fatty acids (e.g., propionate) in situ is crucial for identifying responsive cellular populations.
• Propionate plays significant roles in human health and disease.

Purpose of the Study:

• To develop a bacterial fluorescence-based biosensor for detecting propionate.
• To achieve detection at the millimolar scale in low-volume samples.
• To optimize the biosensor's application protocol across different culture media.

Main Methods:

• Utilized Escherichia coli strain BL21(DE3) transformed with the pPro24-GFP plasmid.
• The plasmid contains the green fluorescent protein (GFP) gene under a propionate-inducible promoter.
• Propionate detection was achieved with a 10 mM threshold in 750 μL samples.

Main Results:

• The biosensor demonstrated reliable propionate detection in Luria-Bertani and Dulbecco's modified Eagle media.
• Fluorescence intensities reached 3863 ± 957 arbitrary units.
• Validation via ROC curve showed substantial agreement (Cohen's kappa = 0.716); proof-of-concept successful in mock fecal samples.

Conclusions:

• A cost-effective, easy-to-use protocol for propionate detection in biological samples was established.
• This offers a proof-of-concept for potential clinical diagnostic applications.
• The biosensor could monitor disease progression and therapeutic interventions, particularly for gastrointestinal disorders where propionate is a biomarker.