title: Nicosulfuron application in agricultural soils drives the selection towards NS-tolerant microorganisms harboring various levels of sensitivity to nicosulfuron.
abstract: The action mode of sulfonylurea herbicides is the inhibition of the acetohydroxyacid synthase (AHAS) required for the biosynthesis of amino acids valine and isoleucine in plants. However, this enzyme is also present in a range of non-targeted organisms, among which soil microorganisms are known for their pivotal role in ecosystem functioning. In order to assess microbial toxicity of sulfonylurea herbicide nicosulfuron (NS), a tiered microcosm (Tier I) to field (Tier II) experiment was designed. Soil bacteria harboring AHAS enzyme tolerant to the herbicide nicosulfuron were enumerated, isolated, taxonomically identified, and physiologically characterized. Results suggested that application of nicosulfuron drives the selection towards NS-tolerant bacteria, with increasing levels of exposure inducing an increase in their abundance and diversity in soil. Tolerance to nicosulfuron was shown to be widespread among the microbial community with various bacteria belonging to Firmicutes (Bacillus) and Actinobacteria (Arthrobacter) phyla representing most abundant and diverse clusters. While Arthrobacter bacterial population dominated community evolved under lower (Tier II) nicosulfuron selection pressure, it turns out that Bacillus dominated community evolved under higher (Tier I) nicosulfuron selection pressure. Different NS-tolerant bacteria likewise showed different levels of sensitivity to the nicosulfuron estimated by growth kinetics on nicosulfuron. As evident, Tier I exposure allowed selection of populations able to better cope with nicosulfuron. One could propose that sulfonylureas-tolerant bacterial community could constitute a useful bioindicator of exposure to these herbicides for assessing their ecotoxicity towards soil microorganisms.
authors.affiliation: Rudjer Boskovic Institute, Division for Marine and Environmental Research, HR-10002, Zagreb, Croatia. ipetric@irb.hr.
authors.forename: Ines
authors.initials: I
authors.lastname: Petric
authors.affiliation: University of Thessaly, Department of Biochemistry and Biotechnology, Ploutonos 26 and Aeolou Str, 412 21, Larisa, Greece.
authors.forename: Dimitrios G
authors.initials: DG
authors.lastname: Karpouzas
authors.affiliation: INRA, UMR 1347 Agroécologie, BP 86510, 21065, Dijon CEDEX, France.
authors.forename: David
authors.initials: D
authors.lastname: Bru
authors.affiliation: Rudjer Boskovic Institute, Division for Marine and Environmental Research, HR-10002, Zagreb, Croatia.
authors.forename: Nikolina
authors.initials: N
authors.lastname: Udikovic-Kolic
authors.affiliation: Institute of Soil Science and Land Evaluation, Soil Biology Section, University of Hohenheim, Emil-Wolff-Str. 27, 70593, Stuttgart, Germany.
authors.forename: Ellen
authors.initials: E
authors.lastname: Kandeler
authors.affiliation: University of Novi Sad, Faculty of Agriculture, Novi Sad, Serbia.
authors.forename: Simonida
authors.initials: S
authors.lastname: Djuric
authors.affiliation: INRA, UMR 1347 Agroécologie, BP 86510, 21065, Dijon CEDEX, France.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Martin-Laurent
mesh_terms: D000095:Acetolactate Synthase / Q000235:genetics / Q000378:metabolism; D039903:Actinobacteria / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development; D000383:Agriculture; D024881:Drug Resistance, Bacterial / Q000235:genetics; D000068536:Bacillota / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development; D006540:Herbicides / Q000032:analysis / Q000633:toxicity*; D011725:Pyridines / Q000032:analysis / Q000633:toxicity*; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis / Q000633:toxicity*; D013453:Sulfonylurea Compounds / Q000032:analysis / Q000633:toxicity*
chemical_list: D006540:Herbicides; D011725:Pyridines; D012987:Soil; D012989:Soil Pollutants; D013453:Sulfonylurea Compounds; C416723:nicosulfuron; D000095:Acetolactate Synthase
keywords: AHAS enzyme; Agricultural soil; Ecotoxicology; Microbial community; Nicosulfuron; Sulfonylurea herbicides; Tolerant bacteria