Document Type : Original Article
Authors
1
Agricultural Botany Department, (Agricultural Microbiology), Faculty of Agriculture, Kafrelsheikh University, Kafr El-Sheikh 33516, Egypt
2
Agricultural Botany Department, (Agricultural Microbiology), Faculty of Agriculture, Kafrelsheikh University, Kafrelsheikh 33516, Egypt.
3
Soil, Water and Environment Research Institute, Sakha, ARC.
4
Department of Chemistry and Toxicity of Pesticides, Faculty of Agriculture, Kafrelsheikh University, Kafrelsheikh 33516, Egypt
Abstract
Pesticide residues are decomposed by a number of microorganisms and used as a source of nitrogen and carbon. The discovery of new strains capable of tolerating and degrading toxic pesticides can increase the flexibility of strategic planning for environmental decontamination initiatives. Our goal was to isolate bacteria tolerant to different concentrations of 40% dimethoate (0-80 µg L-1) from soil samples, determine the optimization of cultural conditions (pH, temperature and incubation time), and examine the inhibitory/inducing effect on the plant growth enhancing traits. The most effective bacterial isolate was identified by biochemistry and phylogenetics, and was also tested for HPLC biodegradation. Data showed that only one strain (SH1) had the greatest tolerance to dimethoate after 72 hours at the highest concentrations (80 µg L−1), despite the fact that all isolates (SH1–SH7) showed some degree of tolerance. Furthermore, at the greatest concentration of dimethoate, the highest growth was observed by the SH1 isolate, which recorded 0.64 for optimum pH 7, 0.69 for optimum temperature 30 °C, and 0.79 for optimum incubation time 72 h. In the same context, isolate (SH1) recorded positive results in producing IAA, NH3, P solubilization, and siderophores at 60 µg L−1 compared to other tested isolates and different concentrations of dimethoate. Therefore, according to the biochemical characteristics and 16S rRNA sequence, SH1 isolate belonged to Bacillus subtilis that had GenBank accession number OQ347968. According to the results of HPLC biodegradation, after 7 days, B. subtilis OQ347968 had the highest rates of dimethoate elimination (80 mg L-1). These findings imply that B. subtilis OQ347968 has a great deal of ability to degrade dimethoate 40% in a variety of environmental conditions.
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