Toward Integrative Bacterial Monitoring of Metolachlor Toxicity in Groundwater
Common herbicides such as metolachlor (MET), and their transformation products, are frequently detected in groundwater worldwide. Little is known about the response of groundwater bacterial communities to herbicide exposure, and its potential use for ecotoxicological assessment. The response of bact...
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| Format: | Article |
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Frontiers Media S.A.
2018-10-01
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| Series: | Frontiers in Microbiology |
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| Online Access: | https://www.frontiersin.org/article/10.3389/fmicb.2018.02053/full |
| _version_ | 1819106977180024832 |
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| author | Gwenaël Imfeld Ludovic Besaury Bruno Maucourt Stéphanie Donadello Nicole Baran Stéphane Vuilleumier |
| author_facet | Gwenaël Imfeld Ludovic Besaury Bruno Maucourt Stéphanie Donadello Nicole Baran Stéphane Vuilleumier |
| author_sort | Gwenaël Imfeld |
| collection | DOAJ |
| description | Common herbicides such as metolachlor (MET), and their transformation products, are frequently detected in groundwater worldwide. Little is known about the response of groundwater bacterial communities to herbicide exposure, and its potential use for ecotoxicological assessment. The response of bacterial communities exposed to different levels of MET from the Ariège alluvial aquifer (Southwest of France) was investigated in situ and in laboratory experiments. Variations in both chemistry and bacterial communities were observed in groundwater, but T-RFLP analysis did not allow to uncover a pesticide-specific effect on endogenous bacterial communities. To circumvent issues of hydrogeochemical and seasonal variations in situ, groundwater samples from two monitoring wells of the Ariège aquifer with contrasting records of pesticide contamination were exposed to different levels of MET in laboratory experiments. The standard Microtox® acute toxicity assay did not indicate toxic effects of MET, even at 5 mg L-1 (i.e., 1000-fold higher than in contaminated groundwater). Analysis of MET transformation products and compound-specific isotope analysis (CSIA) in laboratory experiments demonstrated MET biodegradation but did not correlate with MET exposure. High-throughput sequencing analysis (Illumina MiSeq) of bacterial communities based on amplicons of the 16S rRNA gene revealed that bacterial community differed mainly by groundwater origin rather than by its response to MET exposure. OTUs correlating with MET addition ranged between 0.4 to 3.6% of the total. Predictive analysis of bacterial functions impacted by pesticides using PICRUSt suggested only minor changes in bacterial functions with increasing MET exposure. Taken together, results highlight MET biodegradation in groundwater, and the potential use of bacterial communities as sensitive indicators of herbicide contamination in aquifers. Although detected effects of MET on groundwater bacterial communities were modest, this study illustrates the potential of integrating DNA- and isotopic analysis-based approaches to improve ecotoxicological assessment of pesticide-contaminated aquifers.
GRAPHICAL ABSTRACTAn integrative approach was develop to investigate in situ and in laboratory experiments the response of bacterial communities exposed to different levels of MET from the Ariége alluvial aquifer (Southwest of France). |
| first_indexed | 2024-12-22T02:46:42Z |
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| institution | Directory Open Access Journal |
| issn | 1664-302X |
| language | English |
| last_indexed | 2024-12-22T02:46:42Z |
| publishDate | 2018-10-01 |
| publisher | Frontiers Media S.A. |
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| series | Frontiers in Microbiology |
| spelling | doaj.art-6d445414d58b49a996124987f4af98f12022-12-21T18:41:29ZengFrontiers Media S.A.Frontiers in Microbiology1664-302X2018-10-01910.3389/fmicb.2018.02053363973Toward Integrative Bacterial Monitoring of Metolachlor Toxicity in GroundwaterGwenaël Imfeld0Ludovic Besaury1Bruno Maucourt2Stéphanie Donadello3Nicole Baran4Stéphane Vuilleumier5Laboratory of Hydrology and Geochemistry, EOST-CNRS, LHyGeS UMR 7517, Université de Strasbourg, Strasbourg, FranceGénétique Moléculaire, Génomique, Microbiologie, GMGM UMR 7156, CNRS, Université de Strasbourg, Strasbourg, FranceGénétique Moléculaire, Génomique, Microbiologie, GMGM UMR 7156, CNRS, Université de Strasbourg, Strasbourg, FranceGénétique Moléculaire, Génomique, Microbiologie, GMGM UMR 7156, CNRS, Université de Strasbourg, Strasbourg, FranceBureau de Recherches Géologiques et Miniéres (BRGM), Orléans, FranceGénétique Moléculaire, Génomique, Microbiologie, GMGM UMR 7156, CNRS, Université de Strasbourg, Strasbourg, FranceCommon herbicides such as metolachlor (MET), and their transformation products, are frequently detected in groundwater worldwide. Little is known about the response of groundwater bacterial communities to herbicide exposure, and its potential use for ecotoxicological assessment. The response of bacterial communities exposed to different levels of MET from the Ariège alluvial aquifer (Southwest of France) was investigated in situ and in laboratory experiments. Variations in both chemistry and bacterial communities were observed in groundwater, but T-RFLP analysis did not allow to uncover a pesticide-specific effect on endogenous bacterial communities. To circumvent issues of hydrogeochemical and seasonal variations in situ, groundwater samples from two monitoring wells of the Ariège aquifer with contrasting records of pesticide contamination were exposed to different levels of MET in laboratory experiments. The standard Microtox® acute toxicity assay did not indicate toxic effects of MET, even at 5 mg L-1 (i.e., 1000-fold higher than in contaminated groundwater). Analysis of MET transformation products and compound-specific isotope analysis (CSIA) in laboratory experiments demonstrated MET biodegradation but did not correlate with MET exposure. High-throughput sequencing analysis (Illumina MiSeq) of bacterial communities based on amplicons of the 16S rRNA gene revealed that bacterial community differed mainly by groundwater origin rather than by its response to MET exposure. OTUs correlating with MET addition ranged between 0.4 to 3.6% of the total. Predictive analysis of bacterial functions impacted by pesticides using PICRUSt suggested only minor changes in bacterial functions with increasing MET exposure. Taken together, results highlight MET biodegradation in groundwater, and the potential use of bacterial communities as sensitive indicators of herbicide contamination in aquifers. Although detected effects of MET on groundwater bacterial communities were modest, this study illustrates the potential of integrating DNA- and isotopic analysis-based approaches to improve ecotoxicological assessment of pesticide-contaminated aquifers. GRAPHICAL ABSTRACTAn integrative approach was develop to investigate in situ and in laboratory experiments the response of bacterial communities exposed to different levels of MET from the Ariége alluvial aquifer (Southwest of France).https://www.frontiersin.org/article/10.3389/fmicb.2018.02053/fullgroundwater contaminationmicrobial ecotoxicologychloroacetanilidesbiodegradationbacterial communitiescompound-specific isotope analysis |
| spellingShingle | Gwenaël Imfeld Ludovic Besaury Bruno Maucourt Stéphanie Donadello Nicole Baran Stéphane Vuilleumier Toward Integrative Bacterial Monitoring of Metolachlor Toxicity in Groundwater Frontiers in Microbiology groundwater contamination microbial ecotoxicology chloroacetanilides biodegradation bacterial communities compound-specific isotope analysis |
| title | Toward Integrative Bacterial Monitoring of Metolachlor Toxicity in Groundwater |
| title_full | Toward Integrative Bacterial Monitoring of Metolachlor Toxicity in Groundwater |
| title_fullStr | Toward Integrative Bacterial Monitoring of Metolachlor Toxicity in Groundwater |
| title_full_unstemmed | Toward Integrative Bacterial Monitoring of Metolachlor Toxicity in Groundwater |
| title_short | Toward Integrative Bacterial Monitoring of Metolachlor Toxicity in Groundwater |
| title_sort | toward integrative bacterial monitoring of metolachlor toxicity in groundwater |
| topic | groundwater contamination microbial ecotoxicology chloroacetanilides biodegradation bacterial communities compound-specific isotope analysis |
| url | https://www.frontiersin.org/article/10.3389/fmicb.2018.02053/full |
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