Metalaxyl Degradation by Mucorales Strains Gongronella sp. and Rhizopus oryzae.

Maria Rosário Martins,Pablo Pereira,Cledir Santos,Nelson Lima,Júlio Cruz-Morais

doi:10.3390/molecules22122225

Maria Rosário Martins, Pablo Pereira + Show 3 more

Open Access

https://doi.org/10.3390/molecules22122225

Copy DOI

Abstract

In this study, the degradation of metalaxyl was investigated in the presence of two Mucorales strains, previously isolated from soil subjected to repeated treatments with this fungicide and selected after enrichment technique. Fungal strains were characterised by a polyphasic approach using phylogenetic analysis of the Internal Transcribed Spacer (ITS) gene region, phenotypic characterisation by Matrix-Assisted Laser Desorption Ionization Time-Of-Flight Mass Spectrometry (MALDI-TOF MS) spectral analysis, and growth kinetics experiments. The strains were identified as Gongronella sp. and Rhizopus oryzae. The fungal growth kinetics in liquid cultures containing metalaxyl fits with Haldane model. Under laboratory conditions, the ability of Gongronella sp. and R. oryzae cultures to degrade metalaxyl was evaluated in liquid cultures and soil experiments. Both species were able to: (a) use metalaxyl as the main carbon and energy source; and (b) degrade metalaxyl in polluted soils, with rates around 1.0 mg·kg−1 d−1. This suggests these strains could degrade metalaxyl in soils contaminated with this fungicide.

Highlights

Metalaxyl [methyl N-(2,6-dimethyl-phenyl)-N-(methoxyacethyl)-alaninate] is an important systemic acylanilide fungicide widely used against downy mildew caused by Oomycetes [1]
Soil strains were identified by Internal Transcribed Spacer (ITS) gene region sequencing (Figure 1)
The two soil strains were different from the other G. butleri with sequences identity below 80%

Summary

Introduction

Metalaxyl [methyl N-(2,6-dimethyl-phenyl)-N-(methoxyacethyl)-alaninate] is an important systemic acylanilide fungicide widely used against downy mildew caused by Oomycetes [1]. Metalaxyl is a racemic mixture of [S(+) and R(−)] enantiomers usually at 1:1 ratio, while Metalaxyl-M typically contains 97.5% of the R-enantiomer and 2.5% of the S-enantiomer [2]. Its fungicidal activity is mainly due to the R-enantiomer [3]. Metalaxyl is soluble in water (8.4 g·L−1 ) and characterised by long half-life values in soil [4]. Due to low soil adsorption and high mobility, metalaxyl has the potential to contaminate groundwaters, which represents a serious environmental threat [5,6]. Metalaxyl has been found in groundwater at concentrations up to 0.49 mg·L−1 , which exceeds the 0.1 mg·L−1

Objectives

Methods

Results