Electrochemically active iron (III)-reducing bacteria in coastal riverine sediments

Area of Science:

• Environmental microbiology
• Biogeochemistry
• Electrochemistry

Background:

• Iron (III)-reducing bacteria (IRB) are vital for organic matter degradation and heavy metal cycling in aquatic sediments.
• Previous research identified co-occurrence of Geobacteraceae and Methanosarcinamazei in IRB enrichments from a coastal gold mining site.
• The IRB community in enriched sediments was dominated by Comamonadacea, Clostridiaceae, Bacillaceae, Bacteroidaceae, and Geobacteraceae.

Purpose of the Study:

• To isolate and characterize iron (III)-reducing bacteria from coastal riverine sediments.
• To investigate the electrochemical activity of isolated IRB strains.
• To expand knowledge on the genus Anaerosinus and its extracellular electron transfer capabilities.

Main Methods:

• Enrichment and isolation of IRB from coastal gold mining site sediments.
• 16S rRNA gene sequencing for bacterial identification.
• Chronoamperometry (CA) and cyclic voltammetry (CV) for electrochemical activity assessment.

Main Results:

• Four IRB strains (JhA, JhB, JhC-1, JhC-2) were isolated, belonging to Anaerosinus, Bacillus, and Clostridium genera.
• All isolates demonstrated iron (III)-reducing capabilities.
• Strain JhA exhibited electrochemical activity, oxidizing ethanol and transferring electrons, identifying it as a novel extracellular electron producer.

Conclusions:

• Coastal riverine sediments harbor cultivable IRB with significant electrochemical activity.
• The genus Anaerosinus includes novel extracellular electron producers capable of reducing iron (III).
• These IRB isolates, particularly strain JhA, show promise for heavy metal bioremediation applications.