Microbial dehalogenation of trichloroacetic acid

Area of Science:

• Microbiology
• Environmental Science
• Biochemistry

Background:

• Trichloroacetic acid (TCA) is a persistent environmental pollutant.
• Previous studies have cast doubt on microbial dehalogenation of TCA due to its poor utilization as a sole carbon source.
• The metabolic pathways for TCA degradation remain unclear.

Purpose of the Study:

• To investigate the microbial degradation of trichloroacetic acid (TCA).
• To elucidate the mechanism of TCA dehalogenation.
• To isolate and identify microorganisms capable of degrading TCA.

Main Methods:

• Isolation of pure and mixed bacterial cultures.
• Cultivation of bacteria in media with TCA and a co-metabolizable substrate.
• Analysis of degradation products, including CO2 and Cl- ions.

Main Results:

• Bacterial cultures degraded TCA only when a readily metabolizable co-substrate was present.
• TCA dehalogenation produced CO2 and Cl- ions, but not oxalate.
• A novel decarboxylation mechanism for TCA dehalogenation was proposed, potentially producing carbon monoxide.
• Pseudomonas carboxydohydrogens, a carboxytroph, was identified as a key organism.

Conclusions:

• Microbial degradation of TCA is feasible with the presence of a co-substrate.
• A new pathway for TCA dehalogenation involving decarboxylation is proposed.
• The identified bacterial isolates, particularly P. carboxydohydrogens, play a role in TCA bioremediation.