Michel Caroline, Baran Nicole, André Laurent, Charron Mickael, Joulian Catherine
BRGM, DEPA (Direction de l'Eau, de l'Environnement, des Procédés et Analyses), Orléans, France.
Université d'Orléans, CNRS, BRGM, UMR 7327 Institut des Sciences de la Terre d'Orléans, Orléans, France.
Front Microbiol. 2021 May 13;12:662727. doi: 10.3389/fmicb.2021.662727. eCollection 2021.
The impact of two pesticides (S-metolachlor and propiconazole) and their respective main metabolites (ESA-metolachlor and 1,2,4-triazole) on bacterial denitrification in groundwater was studied. For this, the denitrification activity and the bacterial diversity of a microbial community sampled from a nitrate-contaminated groundwater were monitored during 20 days in lab experiments in the presence or absence of pesticides or metabolites at 2 or 10 μg/L. The kinetics of nitrate reduction along with nitrite and NO production all suggested that S-metolachlor had no or only little impact, whereas its metabolite ESA-metolachlor inhibited denitrification by 65% at 10 μg/L. Propiconazole and 1,2,4-triazole also inhibited denitrification at both concentrations, but to a lesser extent (29-38%) than ESA-metolachlor. When inhibition occurred, pesticides affected the reduction of nitrate into nitrite step. However, no significant differences were detected on the abundance of nitrate reductase and genes, suggesting an impact of pesticides/metabolites at the protein level rather than on denitrifying bacteria abundance. 16S rRNA gene Illumina sequencing indicated no major modification of bacterial diversity in the presence or absence of pesticides/metabolites, except for ESA-metolachlor and propiconazole at 10 μg/L that tended to increase or decrease Shannon and InvSimpson indices, respectively. General growth parameters suggested no impact of pesticides, except for propiconazole at 10 μg/L that partially inhibited acetate uptake and induced a decrease in microbial biomass. In conclusion, pesticides and metabolites can have side effects at environmental concentrations on microbial denitrification in groundwater and may thus affect ecosystem services based on microbial activities.
研究了两种农药（异丙甲草胺和丙环唑）及其各自的主要代谢产物（ESA-异丙甲草胺和1,2,4-三唑）对地下水中细菌反硝化作用的影响。为此，在实验室实验中，在存在或不存在浓度为2或10μg/L的农药或代谢产物的情况下，对从受硝酸盐污染的地下水中采集的微生物群落的反硝化活性和细菌多样性进行了20天的监测。硝酸盐还原动力学以及亚硝酸盐和一氧化氮的产生均表明，异丙甲草胺没有影响或影响很小，而其代谢产物ESA-异丙甲草胺在10μg/L时可抑制反硝化作用达65%。丙环唑和1,2,4-三唑在两种浓度下也均抑制反硝化作用，但程度低于ESA-异丙甲草胺（29%-38%）。当发生抑制作用时，农药会影响硝酸盐还原为亚硝酸盐的步骤。然而，在硝酸盐还原酶和相关基因的丰度上未检测到显著差异，这表明农药/代谢产物的影响发生在蛋白质水平，而非反硝化细菌的丰度上。16S rRNA基因的Illumina测序表明，在存在或不存在农药/代谢产物的情况下，细菌多样性没有重大变化，但10μg/L的ESA-异丙甲草胺和丙环唑分别倾向于增加或降低香农指数和逆辛普森指数。一般生长参数表明农药没有影响，但10μg/L的丙环唑部分抑制了乙酸盐的摄取并导致微生物生物量下降。总之，农药和代谢产物在环境浓度下可能对地下水中的微生物反硝化作用产生副作用，从而可能影响基于微生物活动的生态系统服务。
