Inoculation of Sinorhizobium saheli YH1 Leads to Reduced Metal Uptake for Leucaena leucocephala Grown in Mine Tailings and Metal-Polluted Soils

Abstract

Metalliferous mine tailings have a negative impact on the soil environment near mining areas and render cultivable lands infertile. Phytoremediation involving the synergism of legume and rhizobia provides a useful technique in tackling this issue with cost-effective, environmentally friendly, and easy-to-use features under adverse soil conditions. Leucaena leucocephala has been found to build symbiotic relationships with native rhizobia in the iron-vanadium-titanium oxide (V-Ti magnetite) mine tailing soil. Rhizobia YH1, isolated from the root nodules of L. leucocephala, was classified as Sinorhizobium saheli according to similarity and phylogenetic analyses of 16S rRNA, housekeeping and nitrogen fixation genes. Besides nitrogen fixation, S. saheli YH1 also showed capabilities to produce indole-acetic acid (IAA) (166.77 ± 2.03 mg l−1) and solubilize phosphate (104.41 ± 7.48 mg l−1). Pot culture experiments showed that strain YH1 increased the biomass, plant height and root length of L. leucocephala by 67.2, 39.5 and 27.2% respectively. There was also an average increase in plant N (10.0%), P (112.2%) and K (25.0%) contents compared to inoculation-free control. The inoculation of YH1 not only reduced the uptake of all metals by L. leucocephala in the mine tailings, but also resulted in decreased uptake of Cd by up to 79.9% and Mn by up to 67.6% for plants grown in soils contaminated with Cd/Mn. It was concluded that S. saheli YH1 possessed multiple beneficial effects on L. leucocephala grown in metalliferous soils. Our findings highlight the role of S. saheli YH1 in improving plant health of L. leucocephala by reducing metal uptake by plants grown in heavy metal-polluted soils. We also suggest the idea of using L. leucocephala-S. saheli association for phytoremediation and revegetation of V-Ti mine tailings and soils polluted with Cd or Mn.

Assessment of PGP traits of Bacillus cereus NDRMN001 and its influence on Cajanus cajan (L.) Millsp. phytoremediation potential on metal-polluted soil under controlled conditions

“…Moreover, the seedling, which is susceptible to infection, lower yield, etc., could reduce these metal contents’ large volume ( Hussain et al., 2019 ). Besides that, metal pollutants can contaminate the food chain and pass through the uptake of the foods obtained from metal-contaminated sites ( Kang et al., 2018 ). Any crops will extract a few percent of metals in their tissues or people that consume parts of plants (leaf, fruits, etc.)…”

“…Each enzyme-related metabolic activity is directly related to the pH conditions of the bacterial surroundings ( Hmaeid et al., 2019 ). The pH requirement of bacteria might vary from acidic to alkaline, based on the origin ( Kang et al., 2018 ). Similarly, the B. cereus NDRMN001 was isolated from slightly acidic environmental conditions like pH 6.…”

“…It was previously identified that it had metal tolerance and degradation potential and could be applied on metal-polluted soils as a bioremediation agent and soil fertility-enhancing PGP bacterium ( Narayanan et al., 2020c ). Therefore, this multi-potential B. cereus NDRMN001 could support and improve the phytoremediation potential of the plant by reducing the metal toxicity and providing the PGP components under metal stress conditions ( Kang et al., 2018 ). The chlorophylls (including a and b ) and carotenoids are pivotal photosynthetic pigments in plants used to convert solar energy to chemical energy through the photosynthesis process ( Raza et al., 2020 ).…”

“…Soil is an important factor in many ecological processes, and majority of the creatures that live on Earth rely on it for the successful completion of their lives ( Kang et al., 2018 ). Unfortunately, industrial revolution and modern agricultural practices have caused widespread soil pollution over the last few decades ( Khan et al., 2017 ).…”

Nickel mine soil is a potential source for soybean plant growth promoting and heavy metal tolerant rhizobia

“…Based on the BOX-A1R PCR fingerprints, eight representative rhizobial isolates were selected for the test of plant growth promotion ability using Leonard jars. Leonard jar and nitrogen-free nutrient solution were prepared as previously described ( Kang et al, 2018 ; Yu et al, 2017 ). Soybean seeds were surface-sterilized and germinated as described above.…”