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Pathways of microbial metabolism of parathion
Abstract:
A mixed bacterial culture, consisting of a minimum of nine isolates, was adapted to growth on technical parathion (PAR) as a sole carbon and energy source. The primary oxidative pathway for PAR metabolism involved an initial hydrolysis to yield diethylthiophosphoric acid and p-nitrophenol. A secondary oxidative pathway involved the oxidation of PAR to paraoxon and then hydrolysis to yield p-nitrophenol and diethylphosphoric acid. Under low oxgen conditions PAR was reduced via a third pathway to p-aminoparathion and subsequently hydrolyzed to p-aminophenol and diethylthiophosphoric acid. PAR hydrolase, an enzyme produced by an isolate from the mixed culture, rapidly hydrolyzed PAR and paraoxon (6.0 mumol/mg per min). This enzyme was inducible and stable at room temperature and retained 100% of its activity when heated for 55 C for 10 min.
Insights
This study shows a mixed bacterial culture can degrade technical parathion (PAR) using multiple pathways. A key enzyme, PAR hydrolase, efficiently breaks down PAR and paraoxon, remaining stable under various conditions.
Area of Science:
- Environmental Microbiology
- Bioremediation
- Biochemistry
Background:
- Technical parathion (PAR) is a widely used organophosphate insecticide.
- Effective bioremediation strategies are needed to mitigate PAR contamination.
- Understanding microbial degradation pathways is crucial for developing remediation technologies.
Purpose of the Study:
- To investigate the microbial degradation pathways of technical parathion (PAR).
- To identify and characterize key enzymes involved in PAR metabolism.
- To assess the stability and efficiency of PAR-degrading enzymes.
Main Methods:
- Adaptation of a mixed bacterial culture to utilize technical parathion (PAR) as a sole carbon and energy source.
- Elucidation of PAR metabolic pathways through analysis of intermediate products under varying oxygen conditions.
- Isolation and characterization of PAR hydrolase enzyme from a bacterial isolate.
Main Results:
- A mixed bacterial culture demonstrated the ability to grow on technical parathion (PAR).
- Three distinct metabolic pathways for PAR degradation were identified: primary oxidation, secondary oxidation (via paraoxon), and reduction under low oxygen.
- PAR hydrolase enzyme exhibited rapid hydrolysis of PAR and paraoxon (6.0 μmol/mg/min) and was found to be inducible and stable at room temperature and 55°C for 10 minutes.
Conclusions:
- Mixed bacterial cultures can effectively degrade technical parathion (PAR) through diverse metabolic routes.
- PAR hydrolase is a significant enzyme in parathion degradation, showing high activity and stability.
- The findings support the potential of microbial bioremediation for parathion-contaminated environments.