Quantitative chemical biosensing by bacterial chemotaxis in microfluidic chips

Area of Science:

• Microfluidics
• Biosensing
• Microbial Ecology

Background:

• Whole-cell bacterial bioreporters offer an alternative to chemical analysis for environmental monitoring.
• Current bioreporter assays, reliant on reporter gene induction, have slow response times (30 min to hours), limiting practical applications.
• Faster bioreporter assays are needed for real-time environmental monitoring and chemical sensing.

Purpose of the Study:

• To explore quantitative chemical sensing using bacterial chemotaxis for faster bioreporter assays.
• To develop a microfluidic system for quantifying bacterial chemotaxis in response to chemical gradients.
• To demonstrate the potential of chemotaxis-based sensing for environmental toxicant detection.

Main Methods:

• Utilized a microfluidic chip with a 600 µm-wide chemical gradient stabilized by parallel flow to quantify bacterial chemotaxis.
• Employed transport and chemotaxis steady-state and kinetic modeling to support experimental data.
• Quantified chemotaxis of Escherichia coli towards serine, aspartate, and methylaspartate, and Cupriavidus pinatubonensis JMP134 towards 2,4-dichlorophenoxyacetate.

Main Results:

• Escherichia coli chemotaxis enrichment showed a sharp increase between 0 and 10 µM serine, saturating at 100 µM.
• Maximal chemotaxis accumulation rate for E. coli was observed at 10 µM serine, with observable cell enrichment within 5 minutes.
• Demonstrated the quantification of Cupriavidus pinatubonensis JMP134 chemotaxis towards the herbicide 2,4-dichlorophenoxyacetate.

Conclusions:

• Bacterial chemotaxis can be quantified within minutes, offering a significantly faster readout than traditional bioreporter assays.
• Chemotaxis-based sensing holds promise for developing rapid biosensing platforms for environmental pollutants.
• This approach provides a flexible method for chemical targeting in environmental monitoring applications.