Hexavalent molybdenum reduction to Mo-blue by Acinetobacter calcoaceticus

Area of Science:

• Microbiology
• Environmental Science
• Biochemistry

Background:

• Molybdenum is an essential trace element crucial for various biological processes.
• Microbial reduction of molybdate can be harnessed for bioremediation and metal recovery.
• Understanding the mechanisms of microbial molybdate reduction is vital for optimizing these applications.

Purpose of the Study:

• To isolate and identify a novel bacterium capable of reducing molybdate.
• To optimize the conditions for molybdate reduction and Mo-blue production.
• To investigate the influence of various factors, including electron donors, nutrients, metal ions, and inhibitors, on the reduction process.

Main Methods:

• Isolation and identification of a molybdenum-reducing bacterium using Biolog GN plates and 16S rDNA analysis.
• Optimization of molybdate reduction conditions (temperature, pH, dissolved oxygen).
• Assessing the effect of different electron donors, molybdate and phosphate concentrations, metal ions, and respiratory inhibitors on Mo-blue production.

Main Results:

• Acinetobacter calcoaceticus strain Dr.Y12 was identified as a potent molybdate-reducing bacterium.
• Optimal conditions for Mo-blue production were determined as low dissolved oxygen, 37°C, pH 6.5, with glucose or fructose as preferred electron donors.
• Phosphate concentration significantly impacted Mo-blue production, with inhibition at higher levels. Heavy metals inhibited reduction, while respiratory inhibitors did not, suggesting the electron transport system is not involved.

Conclusions:

• Acinetobacter calcoaceticus strain Dr.Y12 is a promising candidate for microbial molybdate reduction.
• The study elucidates key factors controlling Mo-blue production, offering insights for bioremediation and metal recovery strategies.
• The mechanism of molybdate reduction in this bacterium likely bypasses the conventional electron transport chain.