Accelerated Biodegradation of the Agrochemical Ametoctradin by Soil-Derived Microbial Consortia.

Hunter D Whittington,M Andrea Azcárate-Peril,Mahatam Singh,Chanh Ta,José M Bruno-Bárcena

doi:10.3389/fmicb.2020.01898

Abstract

Pesticide-resistant plant pathogens are an increasing threat to the global food supply and have generated a need for novel, efficacious agrochemicals. The current regulatory process for approving new agrochemicals is a tedious but necessary process. One way to accelerate the safety evaluation process is to utilize in vitro systems to demonstrate pesticide degradation by soil microbes prior to ex vivo soil evaluations. This approach may have the capability to generate metabolic profiles free of inhibitory substances, such as humic acids, commonly present in ex vivo soil systems. In this study, we used a packed-bed microbial bioreactor to assess the role of the natural soil microbial community during biodegradation of the triazolopyrimidine fungicide, ametoctradin. Metabolite profiles produced during in vitro ametoctradin degradation were similar to the metabolite profiles obtained during environmental fate studies and demonstrated the degradation of 81% of the parent compound in 72 h compared to a half-life of 2 weeks when ametoctradin was left in the soil. The microbial communities of four different soil locations and the bioreactor microbiome were compared using high throughput sequencing. It was found that biodegradation of ametoctradin in both ex vivo soils and in vitro in the bioreactor correlated with an increase in the relative abundance of Burkholderiales, well characterized microbial degraders of xenobiotic compounds.

Highlights

The human population has rapidly increased since the development of farming; the current growth rate is unsustainable and will eventually become limited by food demands that cannot persist using our current farming practices (Alexandratos, 1999; Tilman et al, 2002)
Soil samples were collected from four different locations previously utilized for ametoctradin environmental fate testing and regularly used for agricultural studies: California (CA), New Jersey (NJ), and Germany (LUFA 2.2 and LUFA 2.3) (Table 1)
This study examined the ability of an in vitro dynamic packed-bed bioreactor system (PBBR) to simulate agrochemical metabolite degradation profiles found in ex vivo soil experiments

Summary

Introduction

The human population has rapidly increased since the development of farming; the current growth rate is unsustainable and will eventually become limited by food demands that cannot persist using our current farming practices (Alexandratos, 1999; Tilman et al, 2002). This regulation states that for safety before an agrochemical product can be approved for use it must be demonstrated that its residues, products of its degradation, and/or any other ingredients in the formulation do not cause adverse effects on human health and the environment (Federal Insecticide, Fungicide, and Rodenticide Act, 1910) These requirements present a unique challenge to agrochemical companies which must retrieve the agrochemical residues and products of their degradation from the soil for characterization and to show that these residues are not unreasonably harmful. This process can be costly and time-consuming, with environmental fate studies for single compounds lasting nearly a year (McDonald et al, 2006)

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Conclusion