Isolation and characterization of imidacloprid degrading bacteria
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Date
2017
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CCSHAU
Abstract
Imidacloprid, a chloronicotinyl insecticide is used in various crops like, cotton, rice, cereal, maize, sunflowers,
potatoes and vegetables for the control of biting and sucking insects, including rice hoppers, aphids, thrips, whiteflies,
termites, turf insects. So, there is strong need to remediate imidacloprid. The best method used is bioremediation using
microorganisms mainly because of its eco-friendliness and cost effectiveness. During the present investigation, thirty one
mutually morphologically distinct bacterial isolates were obtained from imidacloprid contaminated soil samples from
Jalalpur kalan village and HAU fields by enrichment culture technique. Eight bacterial isolates showed growth up to
30,000 ppm imidacloprid amended in Mineral salt medium (MSM) containing glucose (0.2%). Out of eight, four isolates
showing good growth onMSM agar plates containing 30,000 ppm of imidacloprid were selected for different carbon and
nitrogen source utilization pattern on MSM agar plates. All the isolates showed good growth in presence of five different
carbon and nitrogen sources. Therefore, these carbon and nitrogen sources were selected for imidacloprid utilization in
MSM.More bacterial count and protein content was observed in the medium amended with glucose as carbon source and
ammonium chloride as nitrogen source as compared to medium amended with other carbon and nitrogen sources with all
the four isolates.
To study the utilization of imidacloprid in liquid medium (containing glucose and ammonium chloride),
medium was amended with 100 ppm imidacloprid. After 7 days of growth, residual imidacloprid was determined
in the medium. Maximum utilization of imidacloprid was found with the isolate IP5 (83%) followed by IP1 (82.2
%), IP6 (74.5%) and IP7 (55.1%) respectively.
Growth of four selected isolates was studied in sterilized as well as unsterilized soil amended with imidacloprid
(100 ppm) for a period of two months under laboratory conditions. Viable count was higher in imidacloprid amended soil
as compared to unamended soil with all the isolates. Imidacloprid level decreased in all the treatments. Percent
degradation of imidacloprid was found more in unsterilized soil as compared to sterilized soil. Maximum utilization of
imidacloprid was found with the isolate IP5 (76.0 %) followed by IP1 (73.0 %), IP6 (72.0%) and IP7 (57%) in sterilized
soil. Similar trend was observed in unsterilized soil i.e. maximum utilization of imidacloprid with the isolate IP5 (82.2 %)
followed by IP1 (80.9 %), IP6 (77.27%) and IP7 (68.34 %) respectively.
A pot experiment was conducted to evaluate the potential of the two imidacloprid utilizing bacterial
isolates IP1 and IP5 in the presence of cotton plants under natural conditions. Germination of seeds was not
observed in the treatments amended with 200 ppm imidacloprid. Shoot and root growth was found to be
significantly higher in the inoculated treatments amended with 50-100 ppm imidacloprid as compared to their
respective uninoculated treatments. Significant decrease in imidacloprid content was observed in soil on
inoculation with bacterial isolates.
Promising isolates were identified on the basis of 16 s rDNA gene sequencing. Bacterial isolate IP1 was
found to be most similar to Bacillus pumilus strain NFB1 and IP5 was found to be most similar to Bacillus
aryabhattai.
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