Biodegradation mechanism of 1H-1,2,4-triazole by a newly isolated strain Shinella sp. NJUST26.

Haobo Wu,Lianjun Wang,Jiansheng Li,Jinyou Shen,Xiuyun Sun,Ruiqin Wu,Weiqing Han

doi:10.1038/srep29675

Abstract

The highly recalcitrant 1H-1,2,4-triazole (TZ) is widely used in the synthesis of agricultural pesticide and considered to be an environmental pollutant. In this study, a novel strain NJUST26 capable of utilizing TZ as the sole carbon and nitrogen source, was isolated from TZ-contaminated soil, and identified as Shinella sp. The biodegradation assays suggested that optimal temperature and pH for TZ degradation by NJUST26 were 30 °C and 6–7, respectively. With the increase of initial TZ concentration from 100 to 320 mg L−1, the maximum volumetric degradation rate increased from 29.06 to 82.96 mg L−1 d−1, indicating high tolerance of NJUST26 towards TZ. TZ biodegradation could be accelerated through the addition of glucose, sucrose and yeast extract at relatively low dosage. The main metabolites, including 1,2-dihydro-3H-1,2,4-triazol-3-one (DHTO), semicarbazide and urea were identified. Based on these results, biodegradation pathway of TZ by NJUST26 was proposed, i.e., TZ was firstly oxidized to DHTO, and then the cleavage of DHTO ring occurred to generate N-hydrazonomethyl-formamide, which could be further degraded to biodegradable semicarbazide and urea.

Highlights

Physico-chemical methods such as adsorption[8], sorption[9], photocatalyzed mineralization[10] and electrochemical oxidation[11] have been developed for the degradation or transformation of TZ and its derivatives
A novel strain, which could utilize TZ as the sole carbon and nitrogen source was isolated from TZ-contaminated soil
In order to further identify NJUST26, the 16S rDNA sequence was determined. 16S rDNA fragment comprised of 1353 nucleotides was sequenced and submitted to the National Center for Biotechnology Information (NCBI) for BLAST analysis

Summary

Introduction

Physico-chemical methods such as adsorption[8], sorption[9], photocatalyzed mineralization[10] and electrochemical oxidation[11] have been developed for the degradation or transformation of TZ and its derivatives. For the treatment of recalcitrant contaminants such as TZ, bioaugmentation of the conventional biological systems with specific microbes could be an effective method to achieve high removal efficiency[12]. The isolation of species capable of degrading TZ is rather crucial for formulating an effective stratege for the bioremediation of TZ contaminants. Some species, such as Bacillus[12], Enterobacter and Serratia[13], Kitasatospora and Streptomyces[14], Pseudomonas[15], Trichoderma[16] and Shinella[17], have been reported to degrade the derivatives of TZ, such as triazophos, tebuconazole, ipconazole, propiconazole and www.nature.com/scientificreports/. This study will provide a new biological alternative for the bioremediation of sites contaminated by triazole, through the application of the TZ-degrading strain

Methods

Results

Discussion

Conclusion