Effect of Heavy metals Fe, Cu, and Zn on Soil Free-Living N-Fixing Bacteria

Document Type : Research Paper

Authors

1 Department of Environmental and Natural Resources, Payame Noor University, Tehran, Iran

2 Plant Protection Department, Faculty of Agriculture, University of Tabriz, Tabriz, Iran

Abstract

Nitrogen-fixing bacteria play a crucial role in sustainable agriculture by enhancing soil fertility and reducing the need for chemical fertilizers. However, heavy metal pollution, particularly from iron (Fe), copper (Cu), and zinc (Zn), poses a significant threat to these beneficial microorganisms. This study investigates the effects of three heavy metals - iron (Fe), copper (Cu), and zinc (Zn) - on the populations of two free-living nitrogen-fixing bacterial strains, Azospirillum irakense (AR) and Azotobacter chroococcum (AC), under controlled laboratory conditions. The experimental treatments included sulfate ion (SO4-) solutions of Fe, Cu, and Zn at four concentrations (0.1, 1, 10, and 100 mg/L), alongside a control group. The results revealed that Zn had the most pronounced inhibitory effect, with population reductions of up to 76% for AR and 80% for AC at the highest concentration of 100 mg/L. Cu also exhibited significant inhibitory effects, particularly at higher concentrations, reducing AR and AC populations by 28% and 15%, respectively, at 100mg/L. Lower concentrations of Cu (0.1 and 1mg/L) showed no significant impact on the bacterial populations. In contrast, Fe did not demonstrate any significant inhibitory effects across all tested concentrations. Additionally, we investigated the accumulation of heavy metals within bacterial cells and the production of reactive oxygen species under metal stress. Both experiments revealed significant intracellular metal accumulation and elevated ROS levels at higher metal concentrations, further elucidating the mechanisms of metal toxicity. These findings highlight the potential risks associated with the accumulation of heavy metals, particularly Zn and Cu, in agricultural soils.

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References

Alengebawy, A., Abdelkhalek, S.T., Qureshi, S.R., and Wang, M.Q. 2021. Heavy Metals and Pesticides Toxicity in Agricultural Soil and Plants: Ecological Risks and Human Health Implications. Toxics. 9(3),42.
Coniglio, A., Mora, V., Puente, M., and Cassán, F. 2019. Azospirillum as Biofertilizer for Sustainable Agriculture. Cham: Springer International Publishing. 45-70.
Fasnacht, M., and Polacek, N. 2021. Oxidative stress in bacteria and the central dogma of molecular biology. Frontiers in Molecular Biosciences. 8, 671037.
Gholami, M., and Etemadifar, Z. 2013. Isolation and molecular identification of a new strain of Microbacterium resistens, capable of tolerating the extreme conditions. Journal of Microbial Biology. 2(5),27-42.
Gupta, N., Singh, M., Gupta, P., Mishra, P., and Gupta, V. 2023. Heavy metal bioremediation and toxicity removal from industrial wastewater. Next‐Generation Algae. 1,163-193.
Hindersah, R., Kamaluddin, N.N., Samanta, S., Banerjee, S., and Sarkar, S. 2020. Role and perspective of Azotobacter in crops production. SAINS TANAH - Journal of Soil Science and Agroclimatology. 17(2),170-179.
Johnson, L.A., and Hug, L.A. 2019. Distribution of reactive oxygen species defense mechanisms across domain bacteria. Free Radical Biology and Medicine. 140, 93-102.
Khakvar, R., Sijam, K., Wong, M. Y., Radu, S., Jones, J., and Thong, K.L. 2008. Genomic diversity of Ralstonia solanacearum strains isolated from banana farms in west Malaysia. Plant Pathology Journal. 7(2),162-167.
Khosravi, H., Khoshru, B., Nosratabad, A.F., and Mitra, D., 2024. Exploring the landscape of biofertilizers containing plant growth-promoting rhizobacteria in Iran: Progress and research prospects. Current Research in Microbial Sciences.100268.
Kushwaha, A.N., Rani, R.A., and Kumar, S.A. 2017. Mechanism of soil-metal-microbe interactions and their implication on microbial bioremediation and phytoremediation. Environmental science and engineering. Biodegradation and Bioremediation. 28, 279-305.
Mehri Yari, F., Pirkharrati, H., Farhadi, K., and Soltanalinezhad, N. 2024. Investigation of heavy metals contamination in east Urmia agricultural soil based on contamination indicates. Environmental Resources Research. 12(2),319-332.
Naghshafkan, F., Pirkharrati, H., Farhadi, K., and Soltanalinejad, N. 2023. Evaluation of some heavy metals’ contamination around Urmia Lake and city by soil pollution indicators. Environmental Resources Research. 11(2),271-282.
Nnaji, N.D., Anyanwu, C.U., Miri, T., and Onyeaka, H. 2024. Mechanisms of Heavy Metal Tolerance in Bacteria: A Review. Sustainability. 16(24),11124.
Patil, A., Chakraborty, S., Yadav, Y., Sharma, B., Singh, S., and Arya, M. 2024. Bioremediation strategies and mechanisms of bacteria for resistance against heavy metals: a review. Bioremediation Journal. 1-33.
Ramazani, S.H.R., and Kargar, M. 2023. Germination and seedling growth of two canola (Brassica napus L.) cultivars under heavy metals. Environmental Resources Research. 11(2), 283-290.
Roy, R. 2021. Effect of cadmium and zinc heavy metals on the soil bacteria isolated from coal mine region. Journal of Advanced Scientific Research. 12(04), 68-77.
Sabourmoghaddam, N. 2017. Comparative assessment of heavy metals changes in the ambient air of two different zones of Tabriz city, Iran. Global Nest Journal. 19(1), 69-73.
Sabourmoghaddam, N. 2024a. Investigating the Concentration of Heavy Metals in the Soil and Water of Sardroud Region; an Industrial and Agricultural Area in Suburb of Tabriz City. Journal of Water and Soil Resources Conservation (WSRCJ). 14(2),1-8. (in Persian)
Sabourmoghaddam, N. 2024b. Investigating the effect of soil contamination with heavy metals on the growth and development of wheat seedlings in greenhouse conditions. Journal of Genetic Engineering and Biosafety. 13 (1),42-50. (in Persian)
Sabourmoghaddam, N., and Shakery, M. 2020. Impact assessment of heavy metals pollution in the air on bacterial microflora of elm trees. Carpathian Journal of Earth and Environmental Sciences. 15(1), 87–92.
Sahrawat, K.Á. 2005. Iron toxicity in wetland rice and the role of other nutrients. Journal of Plant Nutrition. 27(8),1471-1504.
Sharma, S., Kumar, A., Nongthombam, J., and Nakum, K. 2021. A Review on the aspects of Azospirillum: Used as a tool in sustainable agriculture. Bulletin of Environment, Pharmacology and Life Sciences. 10(6),20-31.
Tyagi, J., Ahmad, S., and Malik, M. 2022. Nitrogenous fertilizers: impact on environment sustainability, mitigation strategies, and challenges. International Journal of Environmental Science and Technology. 19, 11649–11672.
Van Acker, H., Gielis, J., Acke, M., Cools, F., Cos, P., and Coenye, T. 2016. The role of reactive oxygen species in antibiotic-induced cell death in Burkholderia cepacia complex bacteria. PloS one. 11(7), e0159837.
Wyszkowska, J., Kucharski, J., Borowik, A., and Boros, E. 2008. Response of bacteria to soil contamination with heavy metals. Journal of Elementology. 13(3),443-453.
Environmental Resources Research
Volume 13, Issue 2
October 2025
Pages 251-260

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