Dynamic changes in microbial communities during the bioremediation of herbicide (chlorimuron-ethyl and atrazine) contaminated soils by combined degrading bacteria

Jian Wang,Huiwen Zhang,Xiujuan Wang,Zhencheng Su,Huanhuan Wang,Xinyu Li,Xu Li,Pankaj Kumar Arora

doi:10.1371/journal.pone.0194753

Abstract

Chlorimuron-ethyl and atrazine are two herbicides with long half-lives in soil; their long-term and excessive application has led to a series of environmental problems. In this study, the strains Chenggangzhangella methanolivorans CHL1 and Arthrobacter sp. ART1 were combined and used for the remediation of chlorimuron-ethyl, atrazine and combined contaminated soils in a microcosm experiment. Changes in chlorimuron-ethyl and atrazine concentrations in soils were monitored, and variations in the soil microbial community were studied by phospholipid fatty acid (PLFA) analysis. The two inoculated degrading strains accelerated the degradation of chlorimuron-ethyl and atrazine in soil, especially in the combined contaminated soil. Addition of the two herbicides and their combination generally decreased the concentrations of total PLFAs, total bacterial PLFAs, Gram-negative and Gram-positive bacterial PLFAs and Shannon-Wiener indices, and changed microbial community composition, whilst stimulating fungal PLFA concentrations. In addition, the combined herbicide treatment had more impact on microbial biomass than the single herbicide treatments. Inoculation treatments significantly relieved the effects of herbicides on soil microbial biomass, diversity and community structure. This study demonstrated that strains CHL1 and ATR1 have the potential to remediate chlorimuron-ethyl, atrazine and combined contaminated soils, and provided valuable information for remediation of chlorimuron-ethyl, atrazine and combined contaminated soils in situ.

Highlights

Herbicides have been widely used all over the world for controlling weeds and have made a great contribution to modern agriculture
Both chlorimuron-ethyl and atrazine concentrations in herbicide contaminated treatments gradually decreased with incubation time
The two herbicides alone and in combination generally decreased the concentrations of total phospholipid fatty acid (PLFA) and the main microbial groups, decreased the Shannon-Wiener indices, and stimulated fungal PLFA concentrations

Summary

Introduction

Herbicides have been widely used all over the world for controlling weeds and have made a great contribution to modern agriculture. The long-term and excessive application of chlorimuron-ethyl and atrazine could result in high concentrations of soil residues. In the north of China, combined soil pollution with chlorimuron-ethyl and atrazine residues often occurs because of the rotation of maize and soybean. Soil chlorimuron-ethyl and atrazine residual pollution could significantly shift the soil microbial community structure and function, and affected the growth of sensitive succeeding crops even at low concentrations [4, 5]. Long-term exposure to atrazine causes breast and ovarian cancer. It may cause circulatory disturbance in poisoned animals. The remediation of chlorimuron-ethyl and atrazine contaminated soil is increasingly necessary and urgent

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Discussion

Conclusion