Abstract

Indiscriminate use of highly toxic pesticides in agriculture has produced soil contamination and deterioration of ecosystems. A promising solution to this environmental problem is bioremediation, which includes the use of bacteria to degrade contaminating substances.

(Objective):  The objective of this work was to isolate, identify, and characterize bacterial strains capable of degrading the pesticides chlorothalonil and chlorpyrifos to determine their potential use in bioremediation of contaminated soils.

(Methodology):   The strains were isolated from agricultural soils using enrichment cultures containing chlorothalonil or chlorpyrifos (20 mg/L) as the sole carbon source. The isolated strains were characterized by their morphology, by their physiological responses to 48 biochemical tests and sensitivity to 1 antibiotics, by their growth kinetics, and in molecular terms (amplification of the gene rDNA 16S).

(Results):   In total, three strains were isolated, one capable of using (and degrading) chlorpyrifos, identified as Stenotrophomonas maltophilia, and two bacterial strains with a partial ability to use chlorothalonil as a carbon source, identified as Enterobacter cloacae and Ochrobactrumanthropi. The three bacterial species are Gram-negative bacilli and have diverse physiological characteristics, including variable resistance to certain antibiotics.

(Conclusion):  It is concluded that the isolated bacteria have biotechnological potential to be incorporated into a bioremediation strategy for contaminated soils, especially for the elimination of chlorpyrifos. Finally, further research perspectives are proposed to determine more efficient processes of chlorothalonil degradation by cometabolism.

Keywords: Bacterial bioremediation; chlorpyrifos; chthalonil; fungicide; insecticide; soil contamination