CO₂/HCO₃^- Accelerates Iron Reduction through Phenolic Compounds.

Area of Science:

• Biochemistry
• Microbiology
• Environmental Science

Background:

• Iron is essential for life but its bioavailability is limited by its oxidation state.
• Ferric iron (Fe3+) is poorly soluble in aerobic environments, necessitating its reduction to ferrous iron (Fe2+) for cellular uptake.
• Excessive intracellular Fe2+ can be toxic due to the Fenton reaction.

Purpose of the Study:

• To investigate the effect of bicarbonate (HCO3-) on the chemical reduction of Fe3+ by phenolic compounds.
• To determine how elevated CO2/HCO3- levels influence intracellular Fe2+ availability and microbial growth.
• To assess the broader environmental relevance of this abiotic iron reduction mechanism.

Main Methods:

• Studied the complex formation rate between Fe3+ and protocatechuic acid in the presence of HCO3-.
• Utilized a DtxR-based Corynebacterium glutamicum reporter strain to measure intracellular Fe2+ availability.
• Quantified biomass-specific fluorescence and growth rates under varying CO2/HCO3- conditions.

Main Results:

• Bicarbonate increased the Fe3+-phenolic compound complex formation rate by 46%, accelerating Fe2+ production.
• Elevated CO2/HCO3- levels significantly increased intracellular Fe2+ availability.
• A minimum 50% increase in biomass-specific fluorescence and stimulated growth were observed in the reporter strain.

Conclusions:

• Bicarbonate acts as an abiotic catalyst, enhancing chemical Fe3+ reduction by phenolic compounds.
• This mechanism increases intracellular Fe2+ availability, promoting microbial growth.
• The findings are relevant to geochemical and biological systems, including soil and the human body, impacting iron distribution and pathogen infectiousness.