Scavenging for Hydroxybenzoic Acids in Cupriavidus necator: Studying Ligand Sensitivity Using a Biosensor-Based...

Area of Science:

• Microbiology
• Biochemistry
• Environmental Science

Background:

• Bacteria like Cupriavidus necator degrade organic compounds, but rapid identification tools are needed.
• Hydroxybenzoic acids are important environmental substrates funneled into central metabolic pathways.
• Understanding bacterial gene activation in response to these compounds is crucial for environmental and metabolic studies.

Purpose of the Study:

• To develop and apply a transcription-factor (TF)-based biosensor for quantifying bacterial gene activation by hydroxybenzoic acids.
• To evaluate the sensitivity of Cupriavidus necator's catabolic gene response to different hydroxybenzoic acids.
• To inform metabolic engineering strategies and understand bacterial adaptation to carbon sources.

Main Methods:

• Development of a TF-based biosensor combining ligand-bound regulator activity with a fluorescent reporter.
• Quantification of gene activation thresholds (ACmin) and half-maximal effective concentrations (EC50) for hydroxybenzoic acids.
• Application of the biosensor to Cupriavidus necator to assess its sensitivity to 2-hydroxybenzoate (2-HBA), 4-hydroxybenzoate (4-HBA), and 3-hydroxybenzoate (3-HBA).

Main Results:

• The biosensor successfully quantified gene activation sensitivity to hydroxybenzoic acids.
• Cupriavidus necator exhibited high sensitivity to 2-HBA (ACmin: 4.8 μM, EC50: 19.91 μM) and 4-HBA (ACmin: 2.4 μM, EC50: 13.06 μM).
• Low thresholds and EC50 values suggest a scavenging characteristic of the associated catabolism.

Conclusions:

• TF-based biosensors are effective for mapping bacterial sensing ranges of environmental compounds.
• The study advances understanding of gene expression regulation evolution in response to carbon source availability.
• Findings can guide metabolic engineering by predicting pathway activation and substrate hierarchies.