Plant Growth Promotion and Selenium Accumulation in Zea Mays in Seleniferous Soils by Selenium Tolerant Bacteria

Selenium (Se) is an essential nutrient for both humans and livestock, but its toxicity becomes particularly evident in soils with naturally high Se concentrations. Conversely, Se deficiency in regions with low soil Se levels can lead to severe health issues. This study focused on the isolation of bacteria from seleniferous agricultural soils (Se content: 6.86 ± 0.12 mg/kg), screening their tolerance to Se, and evaluating their potential for promoting plant growth. Three bacterial isolates, Se3, Se38, and Se5 were selected as Se-tolerant and assessed for their effectiveness in enhancing maize growth and regulating Se uptake in seleniferous soils. These isolates exhibited high tolerance levels, withstanding up to 200 mM selenate and 150 mM selenite. These bacteria were identified as Proteus terrae (Se3), Corynebacterium glutamicum (Se38), and Halopseudomonas formosensis (Se5) based on their 16S rRNA sequence analysis. All three bacterial isolates exhibited plant growth-promoting traits, including indole acetic acid (IAA) production, phosphate solubilization, and siderophore production. Inoculation with Se3, Se38, and Se5 significantly enhanced maize growth by 26.8%, 19.6%, and 21.9%, respectively, compared to the control in seleniferous soil. Additionally, plants inoculated with these strains displayed higher root and shoot biomass than non-inoculated controls. Notably, Se3 inoculation resulted in the greatest reduction in Se uptake in maize tissues compared to Se38 and Se5. This  study demonstrated that selenium-tolerant bacterial isolates, Proteus terrae, Halopseudomonas formosensis, and Corynebacterium glutamicum offer a dual benefit in seleniferous soils by enhancing plant growth and mitigating selenium toxicity. These bacteria exhibit high Se tolerance, promote maize growth, and significantly reduce Se uptake in plant tissues, making them valuable biofertilizers. Moreover, their ability to bioaccumulate or biosorb selenium and convert it into elemental selenium (Se⁰) presents an environmentally friendly solution for bioremediation of Se-contaminated soils. Ultimately, leveraging these Se-tolerant, plant growth-promoting bacteria could transform Se-affected areas into viable agricultural lands.