Impact of Salinity and Copper Stress on the Growth and Physiology of Cyanobacteria: A Comparative Study

Author: Shivaranjan C.S. and G. Abraham

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Abstract

In this present study, we delved into the intricate world of Anabaena doliolum, a nitrogen-fixing cyanobacterium, to investigate how it copes with the combined stressors of salinity and copper exposure. Our study revealed that both salinity and copper stress lead to a significant reduction in growth and key cellular components, including protein, chlorophyll, and phycocyanin. The stress induced by salinity and copper was further evidenced by a decrease in the average filament length and heterocyst frequency of A. doliolum. Salinity treatment was found to enhance the activity of the nitrogen assimilation enzyme, nitrate reductase, while glutamine synthetase and nitrogenase exhibited significant inhibition in their activities. Conversely, copper treatment led to a decrease in the activity of all three nitrogen assimilation enzymes. The deleterious effects on growth, cellular components, and nitrogen assimilation enzymes were exacerbated when A. doliolum was exposed to both salt and copper simultaneously. Both individual and combined exposure to salt and copper was observed to stimulate the activity of antioxidant enzymes, including superoxide dismutase, ascorbate peroxidase, and catalase, as well as the accumulation of proline in the cyanobacterium. The study encountered several challenges, including the necessity to evaluate the synergistic effects of salinity and copper on A. doliolum, as well as the complex interplay of multiple physiological variables under stress conditions. These findings have advanced our understanding of how nitrogen-fixing cyanobacteria respond to the concurrent influence of multiple stressors, with potential implications for the ecological and environmental management of rice fields and similar ecosystems.

Keywords

Cyanobacterium, Salinity stress, Copper stress, N assimilation enzymes, Antioxidant enzymes

Conclusion

Cyanobacteria are significant bioinoculants in agriculture because of their specific ability to transform atmospheric nitrogen into ammonia using solar energy. Extreme temperatures, anaerobiosis, salt, drought, pesticides, and heavy metals are just a few of the environmental challenges that these microbes have evolved to survive. Abiotic stresses such as salinity and heavy metal pollution in rice fields, however, make it difficult to exploit them. In this work, the nitrogen-fixing cyanobacterium Anabaena doliolum is exposed to salt and copper, and their combined effects are investigated. The findings show that both stresses reduced growth as well as biological components including protein, chlorophyll, and phycocyanin. Furthermore, the A. doliolum average filament length and heterocyst frequency decreased as a result of the stress caused by salt and copper. Although salt treatment increased the activity of the enzyme responsible for assimilating nitrogen, nitrate reductase, the other two enzymes, glutamine synthetase and nitrogenase, demonstrated a decrease in activity. All three of the main nitrogen assimilation enzymes' activities were shown to be reduced by the copper treatment. The detoxification of free radicals depends heavily on antioxidant enzymes. Superoxide dismutase, ascorbate peroxidase, and catalase activities were increased when the cyanobacterium A. doliolum was individually and simultaneously exposed to salt and copper. Proline buildup by the cyanobacterium has had similar outcomes.

References

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How to cite this article

Shivaranjan C.S. and G. Abraham (2023). Impact of Salinity and Copper Stress on the Growth and Physiology of Cyanobacteria: A Comparative Study. Biological Forum – An International Journal, 15(9): 104-113.