Plant growth promotion mechanisms of bacteria isolated from a long-term reclaimed smelter waste deposit
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Date
2025-09-29
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Publisher
Springer Nature
Abstract
The use of beneficial bacterial strains is proposed as a nature based practice to support sustainable crop production. Strains exposed to extreme environmental stress may have developed robust stress resistance and the capacity to enhance plant growth under unfavorable conditions. Our study provides the new aspect in characterising bacteria from polluted soil. The novelty of our study was isolation of bacteria from a long-term contaminated site and their testing for plant growth promoting mechanisms. The aim of this research was to characterize bacterial strains, collected from the root zone of grasses growing in a heavily polluted smelter wasteland reclaimed 25 years ago using sewage sludge and by-product lime. Their capability to enhance plant resistance to stresses has not been widely assessed. The activity of the strains was assessed based on mechanisms associated with nutrient uptake: phosphate solubilization, ability to fix atmospheric nitrogen (N), ability to synthesize indole-3-acetic acid (IAA)-like compounds, and mechanisms linked to plant stress tolerance: ACC deaminase production, polysaccharides and biofilm development. Metabolic profiling of the strains was performed. Most strains tested in this study exhibited a range of plant growth promotion mechanisms. All strains solubilized phosphates with medium to high intensity, 14 of 15 isolates produced IAA up to 60 μg/mL, all fixed N from 15.85 to 50.00 mg/ml after 72 h. Thirteen strains survived freeze-drying. Our study enabled clustering bacterial strains with capability to perform certain groups of processes. Strains intensively fixing N in general were also able to intensively produce IAA but rather were not efficient producers of extracellular polymeric substances (EPS). IAA production was negatively correlated with 1-aminocyclopropane-1-carboxylic acid deaminase (ACC) deaminase activity and average carbon utilization intensity. All three strains selected for the pot study (Burkholderia sp., Pseudomonas caspiana, and Phyllobacterium sp.) confirmed the effectiveness in promoting wheat growth both at optimal and low soil moisture. The study shows that 25-years reclaimed smelter wastelands are reservoirs of PGPR strains potentially useful for developing biofertilizers enhancing plant growth and resistance to environmental or climatic stresses in agriculture.
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Keywords
bacteria strains, phosphorus solubilizing bacteria, plant growth promotion, PGPR, plant stress tolerance, smelter wasteland