Molecular characterization of chlorpyrifos degrading bacteria isolated from contaminated dairy farm soils in Nakuru County, Kenya

Micah Nyabiba Asamba; Ezekiel Njeru Mugendi; Paul Sifuna Oshule; Suliman Essuman; Lenny Mwagandi Chimbevo; Norbert Adum Atego

doi:10.1016/j.heliyon.2022.e09176

Molecular characterization of chlorpyrifos degrading bacteria isolated from contaminated dairy farm soils in Nakuru County, Kenya

Heliyon. 2022 Mar 24;8(3):e09176. doi: 10.1016/j.heliyon.2022.e09176. eCollection 2022 Mar.

Authors

Micah Nyabiba Asamba¹, Ezekiel Njeru Mugendi¹, Paul Sifuna Oshule², Suliman Essuman³, Lenny Mwagandi Chimbevo⁴, Norbert Adum Atego⁴

Affiliations

¹ Department of Biochemistry, Microbiology and Biotechnology, Kenyatta University, Nairobi, Kenya.
² Department of Medical Biochemistry, Mount Kenya University, Thika, Kenya.
³ Department of Medical Microbiology, Mount Kenya University, Thika, Kenya.
⁴ Department Pure and Applied Sciences, School of Applied and Health Sciences, Technical University of Mombasa, Mombasa, Kenya.

Abstract

Chlorpyrifos (CP) is an organophosphate widely used as an insecticide and acaricide. Extensive application of CP contaminates ecosystems, polluting the environment and food products, creating health complications to humans due to its neurotoxicity. The study evaluated CP bioremediation by bacteria isolated from dairy farm soils in Nakuru County, Kenya, through enrichment culture technique. The growth response of the bacteria and degradation of chlorpyrifos was monitored every five days using UV-VIS Spectrophotometer (600nm). Enrichment culture technique led to the isolation of eighteen (MA1-MA18) potential CP degraders belonging to the genera Pseudomonas, Stenotrophomonas, Bacillus, Alicaligenes, and Achromobacter. The efficacy of four (4) strains was further investigated using Gas Chromatography-Mass Spectrometry (GC-MS) analysis. The results showed that all four strains significantly degraded chlorpyrifos in Minimum Salt Medium (MSM): Lysinibacillus sp.HBUM206408 (87.16 %), Stenotrophomonas maltophilia (82.04 %), Pseudomonas putida (89.52 %), and Achromobacter insuavis (91.08 %) within 16 days, producing 2-Hydroxy-3, 5, 6-trichloropyridine (TCP) as the main metabolite. Therefore, these strains can be used to degrade chlorpyrifos in contaminated soil. There is a need for further studies to determine the possible mechanisms and other metabolites of chlorpyrifos degradation by the isolates obtained in the study. Besides, future studies should explore the efficacy and survival of the organisms in the contaminated environment.

Keywords: Biodegradation; Bioremediation; Chlorpyrifos; Metabolite; Organophosphate; Spectrophotometer.