Burkholderia thailandensis: the Main Bacteria Biodegrading Fipronil in Fertilized Soil with Assessment by a QuEChERS/GC-MS Method

Due to the expansion of sugarcane crops and the high costs of agricultural inputs, an alternative for fertilization of the soil is the use of humic substances (HS) because they improve its physical-chemical properties. The objective of this study was to assess the biological degradation of fipronil in soil supplemented with HS. For determination of fipronil and its metabolites, we validated a quick, easy, cheap, effective, rugged, and safe gas chromatography-mass spectrometry (QuEChERS/GC-MS) method, which yielded detection and quantification limits of 15.0 and 62.5 ng g-1, respectively. The method presented linearity of 0.99, precision between 1.5 and 10.9%, while the recovery ranged from 78 to 98%, with precision (relative standard deviation (RSD)) < 5%. The strain B. thailandensis of Burkholderia sp. grew under typical conditions for degradation of fipronil. Eight treatments assessed the degradation by B. thailandensis in the presence of HS. The metabolites produced in the experiment, although detected, could not be quantified because they were below the limit of quantification of the method. Our results showed that B. thailandensis has the potential to degrade fipronil, and that HS is not toxic to the microbiota, and does not inactivate fipronil.受甘蔗种植面积扩张与农业投入品成本高企影响，腐殖物质（humic substances, HS）因其可改善土壤理化性质，成为土壤施肥的替代方案。本研究旨在评估施加HS的土壤中氟虫腈（fipronil）的生物降解情况。为测定氟虫腈及其代谢物，本研究对一种结合气相色谱-质谱联用（gas chromatography-mass spectrometry, GC-MS）的快速、简便、廉价、高效、耐用且安全（QuEChERS）前处理方法进行了方法学验证，该方法的检出限与定量限分别为15.0 ng·g⁻¹与62.5 ng·g⁻¹。该方法的线性相关系数为0.99，精密度介于1.5%~10.9%之间，回收率为78%~98%，且以相对标准偏差（relative standard deviation, RSD）计的精密度小于5%。伯克霍尔德菌属（Burkholderia sp.）的泰国伯克霍尔德菌（B. thailandensis）菌株可在适配氟虫腈降解的典型条件下生长。本研究设置8组处理，用以评估HS存在时B. thailandensis对氟虫腈的降解效果。实验中生成的代谢物虽可被检出，但因浓度低于该方法的定量限，无法完成定量分析。研究结果表明，B. thailandensis具备降解氟虫腈的潜力，且HS对土壤微生物群落无毒性，同时不会使氟虫腈失活。