Overexpression of Cu/Zn Superoxide Dismutase (Cu/Zn SOD) in Synechococcus&nbsp; elongatus PCC 7942 for Enhanced Azo Dye Removal through Hydrogen Peroxide Accumulation

ShylajaNaciyar Mohandass; Mangalalakshmi Ragavan; Dineshbabu Gnanasekaran; Uma Lakshmanan; Prabaharan Dharmar; Sushanta Kumar Saha

doi:10.3390/biology10121313

Overexpression of Cu/Zn Superoxide Dismutase (Cu/Zn SOD) in Synechococcus  elongatus PCC 7942 for Enhanced Azo Dye Removal through Hydrogen Peroxide Accumulation

Biology (Basel). 2021 Dec 10;10(12):1313. doi: 10.3390/biology10121313.

Authors

ShylajaNaciyar Mohandass¹, Mangalalakshmi Ragavan¹, Dineshbabu Gnanasekaran¹, Uma Lakshmanan¹, Prabaharan Dharmar¹, Sushanta Kumar Saha²

Affiliations

¹ Department of Marine Biotechnology, National Facility for Marine Cyanobacteria (Sponsored by DBT, Govt. of India), School of Marine Sciences, Bharathidasan University, Tiruchirappalli 620024, Tamil Nadu, India.
² Shannon Applied Biotechnology Centre, Technological University of Shannon, Moylish Park, V94 E8YF Limerick, Ireland.

Abstract

Discharge of recalcitrant azo dyes to the environment poses a serious threat to environmental health. However certain microorganisms in nature have developed their survival strategies by degrading these toxic dyes. Cyanobacteria are one such prokaryotic, photosynthetic group of microorganisms that degrade various xenobiotic compounds, due to their capability to produce various reactive oxygen species (ROS), and particularly the hydrogen peroxide (H₂O₂) when released in their milieu. The accumulation of H₂O₂ is the result of the dismutation of superoxide radicals by the enzyme superoxide dismutase (SOD). In this study, we have genetically modified the cyanobacterium Synechococcus elongatus PCC 7942 by integrating Cu/Zn SOD gene (sodC) from Synechococcus sp. PCC 9311 to its neutral site through homologous recombination. The overexpression of sodC in the derivative strain was driven using a strong constitutive promoter of the psbA gene. The derivative strain resulted in constitutive production of sodC, which was induced further during dye-treated growth. The genetically engineered Synechococcus elongatus PCC 7942 (MS-sodC⁺) over-accumulated H₂O₂ during azo dye treatment with a higher dye removal rate than the wild-type strain (WS-sodC^-). Therefore, enhanced H₂O₂ accumulation through SODs overexpression in cyanobacteria may serve as a valuable bioremediation tool.

Keywords: Synechococcus elongatus PCC 7942; copper/zinc superoxide dismutase (Cu/Zn SOD); cyanobacteria; hydrogen peroxide (H2O2); superoxide dismutase (SOD).