Abstract
Malachite green (MG) is an organic contaminant and the effluents with MG negatively influence the health and balance of the coastal and marine ecosystem. The diverse and abundant microbial communities inhabiting in mangroves participate actively in various ecological processes. Metagenomic sequencing from mangrove sediments was applied to excavate the resources MG-degradation genes (MDGs) and to assess the potential of their corresponding enzymes. A data set of 10 GB was assembled into 33,756 contigs and 44,743 ORFs were predicted. In the data set, 666 bacterial genera and 13 pollutant degradation pathways were found. Proteobacteria and Actinobacteria were the most dominate phyla in taxonomic assignment. A total of 44 putative MDGs were revealed and possibly derived from 30 bacterial genera, most of which belonged to the phyla of Proteobacteria and Bacteroidetes. The MDGs belonged to three gene families, including peroxidase genes (up to 93.54% of total MDGs), laccase (3.40%), and p450 (3.06%). Of the three gene families, three representatives (Mgv-rLACC, Mgv-rPOD, and Mgv-rCYP) which had lower similarities to the closest sequences in GenBank were prokaryotic expressed and their enzymes were characterized. Three recombinant proteins showed different MG-degrading activities. Mgv-rPOD had the strongest activity which decolorized 97.3% of MG (300 mg/L) within 40 min. In addition, Mgv-rPOD showed a more complete process of MG degradation compared with other two recombinant proteins according to the intermediates detected by LC-MS. Furthermore, the high MG-degrading activity was maintained at low temperature (20°C), wider pH range, and the existence of metal ions and chelating agent. Mgv-rLACC and Mgv-rCYP also removed 63.7% and 54.1% of MG (20 mg/L) within 24 h, respectively. The results could provide a broad insight into discovering abundant genetic resources and an effective strategy to access the eco-friendly way for preventing coastal pollution.
Highlights
The application of synthetic dyes is extensive in the fields of textile, pharmaceutical, cosmetics, paper making, solar cells, and acrylic industries (Chang and Lin, 2001)
10 GB of data were generated and the raw reads containing “N” or adaptors were removed from the dataset and the clean reads were retaining for further analysis
10 GB of data was generated and 9.4 GB was remained as clean data
Summary
The application of synthetic dyes is extensive in the fields of textile, pharmaceutical, cosmetics, paper making, solar cells, and acrylic industries (Chang and Lin, 2001). Due to various risks on environment and human health, strategies for the removal of dyes have attracted increasing attention from health professionals and environmentalists Malachite green (MG), in particular, is one typical of synthetic dyes and is widely used in dyeing of silk, leather, and paper, which has been shown to harm humans and animals because of toxicity, mutagenicity, and carcinogenicity (Srivastava et al, 2004; Gopinathan et al, 2015). MG can be metabolized into leucomalachite green (LMG) (Yong et al, 2015) and remains in fish muscles, fat, and organs with a half-life of about 10 days and even longer (Chen and Miao, 2010). Bioremediation strategy may constitute an alternative approach to conventional physicochemical methods, benefiting from the potential of indigenous microorganisms to metabolize anthropogenic compounds (Grosser et al, 1991; Tayabali et al, 2017)
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