Biodegradation potential of deltamethrin by the Bacillus cereus strain Y1 in both culture and contaminated soil

Carboxylesterase, a de-esterification enzyme, catalyzes the degradation of chlorimuron-ethyl in Rhodococcus erythropolis D310-1.

De-esterification is an important degradation or detoxification mechanism of sulfonylurea herbicide in microbes and plants. However, the biochemical and molecular mechanisms of sulfonylurea herbicide de-esterification are still unknown. In this study, a novel esterase gene, sulE, responsible for sulfonylurea herbicide de-esterification, was cloned from Hansschlegelia zhihuaiae S113. The gene contained an open reading frame of 1,194 bp, and a putative signal peptide at the N terminal was identified with a predicted cleavage site between Ala37 and Glu38, resulting in a 361-residue mature protein. SulE minus the signal peptide was synthesized in Escherichia coli BL21 and purified to homogeneity. SulE catalyzed the de-esterification of a variety of sulfonylurea herbicides that gave rise to the corresponding herbicidally inactive parent acid and exhibited the highest catalytic efficiency toward thifensulfuron-methyl. SulE was a dimer without the requirement of a cofactor. The activity of the enzyme was completely inhibited by Ag+, Cd2+, Zn2+, methamidophos, and sodium dodecyl sulfate. A sulE-disrupted mutant strain, ΔsulE, was constructed by insertion mutation. ΔsulE lost the de-esterification ability and was more sensitive to the herbicides than the wild type of strain S113, suggesting that sulE played a vital role in the sulfonylurea herbicide resistance of the strain. The transfer of sulE into Saccharomyces cerevisiae BY4741 conferred on it the ability to de-esterify sulfonylurea herbicides and increased its resistance to the herbicides. This study has provided an excellent candidate for the mechanistic study of sulfonylurea herbicide metabolism and detoxification through de-esterification, construction of sulfonylurea herbicide-resistant transgenic crops, and bioremediation of sulfonylurea herbicide-contaminated environments.

https://aem.asm.org/content/aem/78/6/1962.full.pdf

SulE, a Sulfonylurea Herbicide De-Esterification Esterase from Hansschlegelia zhihuaiae S113

By enrichment culturing of the sludge collected from the industrial wastewater treatment pond, we isolated a highly efficient nicosulfuron degrading bacterium Serratia marcescens N80 In liquid medium, Serratia marcescens N80 grows using nicosulfuron as the sole nitrogen source, and the optimal temperature, pH values, and inoculation for degradation are 30-35°C, 60-70, and 30% (v/v), respectively With the initial concentration of 10 mg L⁻¹, the degradation rate is 936% in 96 hours; as the initial concentrations are higher than 10 mg L⁻¹, the biodegradation rates decrease as the nicosulfuron concentrations increase; when the concentration is 400 mg L⁻¹, the degradation rate is only 531% Degradation follows the pesticide degradation kinetic equation at concentrations between 5 mg L⁻¹ and 50 mg L⁻¹ Identification of the metabolites by the liquid chromatography/mass spectrometry (LC/MS) indicates that the degradation of nicosulfuron is achieved by breaking the sulfonylurea bridge The strain N80 also degraded some other sulfonylurea herbicides, including ethametsulfuron, tribenuron-methyl, metsulfuron-methyl, chlorimuron-ethyl,and rimsulfuron

Biodegradation of nicosulfuron by the bacterium Serratia marcescens N80

Effects of chlorimuron-ethyl application with or without urea fertilization on soil ammonia-oxidizing bacteria and archaea

The chlorimuron-ethyl-degrading bacterium LW3 was isolated from contaminated soil and identified by 16S rRNA gene sequencing as Pseudomonas sp When chlorimuron-ethyl was provided as the sole nitrogen source, the degradation efficiency in liquid medium was about 810% after 7 days of inoculation with strain LW3 The effects of chlorimuron-ethyl concentration and temperature on biodegradation were examined Two metabolites of degradation were analyzed by LC/MS Based on the identified products, strain LW3 seemed to be able to degrade chlorimuron-ethyl by cleavage of the sulfonylurea bridge The inoculation of strain LW3 to chlorimuron-ethyl-treated soil resulted in a higher degradation rate than in uninoculated soil, regardless of the soil being sterilized or nonsterilized This microbial culture has great potential for the bioremediation of soil contaminated with chlorimuron-ethyl

Hui-jie Wang

Papers

Biodegradation of the sulfonylurea herbicide chlorimuron-ethyl by the strain Pseudomonas sp. LW3