Pendimethalin Nitroreductase Is Responsible for the Initial Pendimethalin Degradation Step in Bacillus subtilis Y3

Area of Science:

• Environmental microbiology
• Biochemistry
• Molecular biology

Background:

• Pendimethalin is a widely used herbicide with environmental persistence and bioaccumulative potential.
• Its biodegradation pathways and the enzymes/genes involved remain largely uncharacterized.
• Nitroreduction is a key initial step in pendimethalin degradation and detoxification.

Purpose of the Study:

• To identify and characterize the enzyme responsible for pendimethalin nitroreduction.
• To clone the gene encoding this enzyme.
• To assess the enzyme's potential for herbicide detoxification.

Main Methods:

• Purification of pendimethalin nitroreductase (PNR) from Bacillus subtilis Y3.
• Identification of the PNR gene (pnr) through proteomic analysis.
• Enzymatic assays to determine substrate specificity and reaction products.
• Detoxification assays using Saccharomyces cerevisiae growth inhibition.

Main Results:

• A novel pendimethalin nitroreductase (PNR) was purified from Bacillus subtilis Y3.
• The gene encoding PNR (pnr) was identified and cloned.
• PNR catalyzed the nitroreduction of pendimethalin and other dinitroaniline herbicides (butralin, oryzalin, trifluralin).
• PNR-mediated reduction of pendimethalin detoxified the herbicide, eliminating its toxicity to Saccharomyces cerevisiae.

Conclusions:

• PNR is the first characterized enzyme involved in pendimethalin biodegradation.
• The pnr gene provides a genetic basis for understanding pendimethalin nitroreduction.
• PNR demonstrates significant potential for the bioremediation and detoxification of pendimethalin and related herbicides in the environment.