6533b836fe1ef96bd12a1a6c

RESEARCH PRODUCT

Bacterial hppd: a biomarker of exposure of soils to beta-triketone herbicides?

subject

description

National audience; β-triketone herbicides are among the most used herbicides in corn crop to control broadleaf weeds.These herbicides inhibit the 4-hydroxyphenylpyruvate dioxygenase (4-HPPD) and lead to bleaching anddeath of weeds. This enzyme is not only found in plants but in all living organisms, includingmicroorganisms where it takes part to the tyrosine degradation pathway. Thus, microorganismsclassified as “non-target organisms” by current EU regulation for pesticide authorization, might beimpacted by β-triketones, with possible domino effect on microbial functions supporting soilecosystem services (Thiour-Mauprivez et al. 2019). Since microorganisms have been proposed by EFSAas key-drivers to be monitored to better protect soil ecosystem services, we tested the hypothesis thathppd bacterial community can constitute a biomarker of exposure to β-triketones. Within this context,we developed a toolbox to monitor the abundance, the diversity and the activity of the hppd bacterialcommunity.Abundance and diversity of hppd bacterial community were tested in a lab-to-field experimentaldesign following the tiered-approach recommended by EFSA to conduct pesticide environmental riskassessment (ERA). Under lab conditions, soil microcosms not exposed (control) or exposed to x1 or x10times the agronomical dose of sulcotrione (active ingredient) or Decano® (one of the commercialformulation of sulcotrione) were studied. Under field conditions, samples were collected in corn cropexposed to β-triketones or not (control). Analytical chemistry was applied to all samples to study thedissipation of β-triketone, search for residues and estimate the scenario of exposure of soilmicroorganisms. Nucleic acids (DNA/RNA) were extracted from soil samples. Home-made degeneratedprimers, specific to the hppd gene of soil bacteria, allowed us to measure the abundance (quantitativePCR), the composition (α-diversity) and the diversity (β-diversity) (NGS) of the hppd bacterialcommunity (Thiour-Mauprivez et al. 2020). Finally, the inhibition of the activity of the 4-HPPD wasassessed on pure bacterial strains under wet lab conditions to measure EC50 of β-triketones.Our poster will be presented to the audience with the aim to identify the better proxy of the hppdbacterial community that could be used as a biomarker to reflect the exposure of soil microbialcommunity to β-triketone residues. As a perspective my work might be extended to other pesticidestargeting other enzymes that are also present in so call non-target organisms such as sulfonylureasinhibiting acetohydroxy acid synthase (AHAS).