Selection and identification of deltamethrin-degrading bacteria
Objective To select and identify deltamethrin-degrading bacteria in paddy fields,and to determine their degradation efficiency.Methods A bacterial flora capable of degrading deltamethrin was obtained through domestication,enrichment,isolation,and purification.The species was identified based on morphological and molecular characteristics.For single colonies,the full length of the 16S rRNA gene was sequenced and analyzed,and for the flora,the 16S rRNA V4 region was sequenced using the MiSeq high-throughput method.Sequence annotation and analysis were conducted.Bacterial composition and abundance were described at species and genus levels.The flora was cultured with deltamethrin,bifenthrin,and cyhalothrin separately,and the degrading efficiency was calculated based on the residual concentrations of the insecticides.Results A bacterial flora capable of degrading deltamethrin was obtained from the water of paddy fields.The identified single colonies included Amycolatopsis eurytherma,Acinetobacter baumannii,Ancylobacter sp.,Rhodococcus spp.,Amycolatopsis spp.,Ochrobactrum sp.,and Xanthobacter sp.The MiSeq high-throughput sequencing results showed that bacteria>4%in abundance at the genus level included Pseudomonas(26.78%),Acinetobacter(7.00%),Ochrobactrum(6.82%),Achromobacter(5.00%),Klebsiella(4.39%),Microbacterium(4.12%).The degradation rates of the three pyrethroid insecticides by the bacterial flora continued to increase since day 2,peaking on day 8 the longest observation period at 76.75%(bifenthrin),63.65%(deltamethrin),and 74.20%(cyhalothrin;reaching the plateau on day 6).Conclusions A deltamethrin-degrading bacterial flora was successfully obtained,in which Pseudomonas was the dominant population,showing wide degradation efficiency for pyrethroid insecticides.This study provides basic data for the field application of degrading bacteria and the studies about rapid degradation of insecticides.
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