Fermentation and hydrogen metabolism affect uranium reduction by clostridia

Area of Science:

• Environmental Microbiology
• Biogeochemistry
• Anaerobic Respiration

Background:

• Uranium reduction by clostridia is common but varies significantly between strains.
• Culture pH impacts the efficiency of uranium(VI) reduction.
• Understanding the metabolic basis of uranium reduction is crucial for bioremediation.

Purpose of the Study:

• To characterize the metabolic properties of uranium-reducing clostridial strains.
• To investigate the relationship between hydrogen metabolism and uranium reduction.
• To elucidate the role of hydrogenase in uranium(VI) and iron(III) reduction.

Main Methods:

• High-Performance Liquid Chromatography (HPLC) and Gas Chromatography (GC) for metabolic profiling.
• Fermentation experiments with varying headspace gases (hydrogen vs. nitrogen).
• Assessment of uranium(VI) reduction in the presence/absence of clostridial cells and hydrogen.

Main Results:

• Clostridial strains exhibit diverse metabolic capabilities affecting uranium reduction extent.
• Hydrogen metabolism, particularly hydrogenase activity, is critical for uranium(VI) reduction.
• Uranium reduction is dependent on clostridial cells and hydrogen availability, not hydrogen alone.

Conclusions:

• Hydrogenase plays a vital role in uranium(VI) and iron(III) reduction by clostridia.
• Factors like copper(II) addition or iron depletion can inhibit uranium reduction.
• A comprehensive model linking clostridial metabolism, hydrogen production, and uranium reduction is proposed.