High Throughput Sediment DNA Sequencing Reveals Azo Dye Degrading Bacteria Inhabit Nearshore Sediments.

Mei Zhuang,Wenhua Liu,Ping Li,Edmond Sanganyado,Jianming Zhu,Liang Xu

doi:10.3390/microorganisms8020233

Mei Zhuang, Wenhua Liu + Show 4 more

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https://doi.org/10.3390/microorganisms8020233

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Abstract

Estuaries and coastal environments are often regarded as a critical resource for the bioremediation of organic pollutants such as azo dyes due to their high abundance and diversity of extremophiles. Bioremediation through the activities of azoreductase, laccase, and other associated enzymes plays a critical role in the removal of azo dyes in built and natural environments. However, little is known about the biodegradation genes and azo dye degradation genes residing in sediments from coastal and estuarine environments. In this study, high-throughput sequencing (16S rRNA) of sediment DNA was used to explore the distribution of azo-dye degrading bacteria and their functional genes in estuaries and coastal environments. Unlike laccase genes, azoreductase (azoR), and naphthalene degrading genes were ubiquitous in the coastal and estuarine environments. The relative abundances of most functional genes were higher in the summer compared to winter at locations proximal to the mouths of the Hanjiang River and its distributaries. These results suggested inland river discharges influenced the occurrence and abundance of azo dye degrading genes in the nearshore environments. Furthermore, the azoR genes had a significant negative relationship with total organic carbon, Hg, and Cr (p < 0.05). This study provides critical insights into the biodegradation potential of indigenous microbial communities in nearshore environments and the influence of environmental factors on microbial structure, composition, and function which is essential for the development of technologies for bioremediation in azo dye contaminated sites.

Highlights

The presence of azo dyes in marine environments may pose significant ecological risk since they are highly recalcitrant and toxic [1]
The potential of in situ bioremediation can be determined by establishing the distribution microorganisms and biodegradation functional genes in the contaminated site
Marine environments are often treated as a crucial source of extremophiles that can be isolated, cultured, and developed for biotreatment of textile effluent and azo dye impacted soils

Summary

Introduction

The presence of azo dyes in marine environments may pose significant ecological risk since they are highly recalcitrant and toxic [1]. Several studies detected azo dyes and their potentially toxic aromatic amines in industrial effluent and rivers at concentrations ranging from 0.05 to 316 μg L−1 [3]. Current research has focused on the development of strategies for removing azo dyes from industrial effluent [4,5] and contaminated environments [6]. Azo dyes and their metabolites are highly toxic, carcinogenic, and mutagenic [1]. Exposing Silurana tropicalis (Western clawed frog) larvae to water and sediment containing Disperse Yellow 7 at environmentally relevant concentrations of up to 22 μg L−1 and 209 μg g−1, respectively resulted in a reduction in tadpole survival and an increase in malformations [7]. There is need for a comprehensive understanding of the fate of azo dyes in aquatic environments

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