Pesticides are regularly used for a variety of applications and are disseminated throughout the environment. These substances may have significant negative impacts. To date, the half-life, t, was often used to study the fate of pesticides in environmental matrices (water, soil, sediment). However, this value gives limited information. First, it does not evaluate the formation of by-products, resulting in the need for additional experiments to be performed to evaluate biodegradation and biotransformation products. T also fails to consider the chemical's impact on biodiversity. Resilience time, a new and integrative proxy, was recently proposed as an alternative to t, with the potential to evaluate all the post-application effects of the chemical on the environment. The 'Environmental Metabolic Footprinting' (EMF) approach, giving an idea of the resilience time, was used to evaluate the impact of botanicals on soil. The goal is to optimise the EMF to study the impact of a microbial insecticide, the Bacillus thuringiensis israelensis (Bti), on sediment. The difficulty of this work lies in the commercial solution of Bti that is really complex, and this complexity yields chromatograms that are extremely difficult to interpret; t cannot be used. No methodologies currently exist to monitor the impact of these compounds on the environment. We will test the EMF to determine if it is sensitive enough to tolerate such complex mixtures. A pure chemical insecticide, the α-cypermethrin, will be also studied. The article shows that the EMF is able to distinguish meta-metabolome differences between control and exposed (with Bti) sediments.
Rationale
Correct biomarker determination in metabolomics is crucial for unbiased conclusions and reliable applications. However, this determination is subject to several drifts, e.g. matrix effects and ion suppression in Liquid Chromatography/Mass Spectrometry (LC/MS)‐based approaches. This phenomenon provokes critical issues for biomarker determination, particularly during comparative studies dealing with samples exhibiting heterogeneous complexities.
Methods
Occurrence of the issue was coincidentally noticed when studying the environmental impact of a complex bioinsecticide: Bacillus thuringiensis israelensis. The studied samples comprised insecticide‐spiked sediments and untreated control sediments. QuEChERS extractions followed by LC/ESI‐Q/ToF analyses were performed on sediments after 15 days of incubation. Meta‐metabolomes containing pesticide xenometabolites and sediment endometabolites were analyzed in depth using XCMS‐based computational data preprocessing. Multivariate statistical analyses (PCA, OPLS‐DA) and raw data crosschecks were performed to search for environmental biomarkers.
Results
Multivariate analyses and raw data crosschecks led to the selection of nine metabolites as biomarker candidates. However, when exploring the mass spectra, co‐elutions were noticed between seven of these metabolites and multi‐charged macromolecules originating from the pesticide. Provoked false positives were thus suspected due to a potential ion suppression exclusively occurring in the spiked samples. A dilution‐based approach was then applied. It confirmed five metabolites as suppressed ions.
Conclusions
Ion suppression should be considered as a critical issue for biomarker determination when comparing heterogeneous metabolic profiles. Raw chromatograms and mass spectra crosschecks are mandatory to reveal potential ion suppressions in such cases. Dilution is a suitable approach to filter reliable biomarker candidates before their identification and absolute quantification.
The bis‐triazole ligand and its corresponding copper complexes were synthesized and characterized for the first time and proposed as new labels for the development of electrochemical aptasensors. The bis‐triazole ligand was prepared from methyl 1,6‐heptadiyne‐4‐carboxylate and 2‐(azidomethyl)phenol using classical CuAAC in presence of different copper salts. The X‐ray structure of bis‐triazole showed a symmetry center (C1). UV‐Vis and X‐band EPR spectra showed that the coordination capacity of the bis‐triazole ligand was improved in the presence of triethylamine due to deprotonation of the triazole and phenolate moieties. After complexation with copper, the obtained complex was successfully attached to an anti‐estradiol aptamer through thiol‐maleimide coupling, and the resulting labelled aptamer was immobilized on a carbon screen‐printed electrode by carbodiimide coupling. The electrochemical response of the resulting sensor was shown to decrease in the presence of estradiol, demonstrating that the developed complexes can be applied for the development of aptasensors.
Bioherbicides appear as an ecofriendly alternative to synthetic herbicides, generally used for weed management, because they are supposed to have low side on human health and ecosystems. In this context, our work aims to study abiotic (i.e., photolysis) and biotic (i.e,. biodegradation) processes involved in the fate of leptospermone, a natural β-triketone herbicide, by combining chemical and microbiological approaches. Under controlled conditions, the photolysis of leptospermone was sensitive to pH. Leptospermone has a half-life of 72 h under simulated solar light irradiations. Several transformation products, including hydroxy-leptospermone, were identified. For the first time, a bacterial strain able to degrade leptospermone was isolated from an arable soil. Based on its 16S ribosomal RNA (rRNA) gene sequence, it was affiliated to the Methylophilus group and was accordingly named as Methylophilus sp. LS1. Interestingly, we report that the abundance of OTUs, similar to the 16S rRNA gene sequence of Methylophilus sp. LS1, was strongly increased in soil treated with leptospermone. The leptospermone was completely dissipated by this bacteria, with a half-life time of 6 days, allowing concomitantly its growth. Hydroxy-leptospermone was identified in the bacterial culture as a major transformation product, allowing us to propose a pathway of transformation of leptospermone including both abiotic and biotic processes.
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