Biodegradation of the fungicide propiconazole by Pseudomonas aeruginosa PS-4 strain isolated from a paddy soil

Abstract

In India, propiconazole, a triazole group fungicide, is broadly used against powdery mildew, rusts, and leaf spot diseases of cereals and coffee. The toxicity of this fungicide is known to affect the quality of the soil. Hence, in the present study, a bacterium isolated from contaminated paddy soil was used to study the degradation of propiconazole under in vitro conditions. The isolated bacterium was confirmed as Pseudomonas aeruginosa strain (PS-4) based on morphological and biochemical characteristics, and 16S rRNA gene sequencing. When the isolated bacterium was grown in mineral salt medium amended with 10 μg/l propiconazole as a sole carbon source, culture filtrates of the bacterium utilized up to 8 μg/L of propiconazole after 72 h of incubation at 30 °C and pH 7, as analyzed by HPLC. Degradation of propiconazole by the bacterium was also aided by the secretion of three metabolites—1,2,4-triazole; 2,4-dichlorobenzoic acid; and 1-chlorobenzene—as determined by their mass spectra. Furthermore, induction of monooxygenase activity and the CYP450 gene was observed in the culture filtrate of strain PS-4, showing evidence of their role in the degradation of propiconazole. These results revealed that PS-4 is an efficient candidate for the reduction of contaminants present in the soil, thereby contributing to soil health and crop improvement.