Biodegradation of malachite green by an endophytic bacterium Klebsiella aerogenes S27 involving a novel oxidoreductase
Endophytic microorganisms can metabolize organic contaminants and assist in plant growth, thus facilitating the phytoremediation of polluted environments. An endophytic bacterium capable of decoloring malachite green (MG) was isolated from the leaves of the wetland plant Suaeda salsa and was identified as Klebsiella aerogenes S27. Complete decolorization of MG (100 mg/l) was achieved in 8 h at 30 °C and pH 7.0. Ultraviolet-visible spectroscopy and Fourier-transform infrared spectroscopy analyses indicated the degradation of MG by the isolate. The enzymic assays of the strain showed the triphenylmethane reductase (TMR) activity. A gene encoding putative TMR-like protein (named as KaTMR) was cloned and heterologously expressed in Escherichia coli. KaTMR showed only 42.6–43.3% identities in amino acids compared with well-studied TMRs, and it phylogenetically formed a new branch in the family of TMRs. The degraded metabolites by recombinant KaTMR were detected by liquid chromatography-mass spectrometry, showing differences from the products of reported TMRs. The biotransformation pathway of MG was proposed. Phytotoxicity studies revealed the less-toxic nature of the degraded metabolites compared to the dye. This study presented the first report of an endophyte on the degradation and detoxification of triphenylmethane dye via a novel oxidoreductase, thus facilitating the study of the plant-endophyte symbiosis in the bioremediation processes.
KeywordsMalachite green Endophytic bacteria Biodegradation Oxidoreductase Detoxification
This study was funded by National Natural Science Foundation of China (Grant No. 31640002), the Natural Science Foundation of Shandong Province (Grant No. ZR2015JL013), the China Postdoctoral Science Foundation (Grant No. 2016 M600551), and the International Postdoctoral Exchange Fellowship, China (Grant No. 20170058).
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Conflict of interest
The authors declare that they have no competing interests.
Research involving human participants and/or animals
This article does not contain any studies with human participants or animals performed by any of the authors.
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