One appropriate strategy for refining heavy metals could be based on bioprecipitation by ureolytic bacteria. The study was conducted to isolate urease-producing bacteria from the contaminated soils and evaluate the potential of selected isolates in biomineralization of heavy metals.To this end, four isolates which had the greatest urease production, calcite precipitation, and endurance to the heavy metals were obtained from contaminated areas during the screening steps. These isolates along with Sporosarcina pasteurii were used to bioprecipitate zinc (Zn), lead (Pb), and cadmium (Cd) from solutions with concentrations of 100, 300, and 500 mM of these metals' ions. Amount of heavy metal precipitates formed by these bacteria were compared.Among these isolates, Stenotrophomonas rhizophila (A323) and Variovorax boronicumulans (C113) produced the highest carbonate minerals of heavy metals. S. rhizophila removed 96.25%, 71.3 %, and 63.91% of Pb, Cd, and Zn, respectively, after 72 h of incubation. Also, V. boronicumulans removed 95.93% of Pb, 73.45% of Cd, and 73.81% of Zn after having the same amount of time for incubation. S. pasteurii eliminated 98.71% of Pb, 97.15% of Cd, and 94.83% of Zn. The presence of lead, zinc, cadmium, and carbon as well as oxygen in precipitates formed from biomineralization of heavy metals was confirmed by energy dispersive spectroscopy (EDS). The S. pasteurii produced higher amounts of metal carbonates. Nevertheless, the use of selected bacteria in bioremediation of contaminated sites may be more effective due to the stability of these bacteria in high concentrations of Pb, Zn, and Cd.

Accumulation of stress ethylene in plants due to osmotic stress is a major challenge for the achievement of optimum sweet corn crop yield with limited availability of irrigation water. A significant increase in earth’s temperature is also making the conditions more crucial regarding the availability of ample quantity of irrigation water for crops production. Plant growth promoting rhizobacteria (PGPR) can play an imperative role in this regard. Inoculation of rhizobacteria can provide resistance and adaptability to crops against osmotic stress. In addition, these rhizobacteria also have potential to solve future food security issues. That's why the current study was planned to examine the efficacious functioning of Pseudomonas fluorescens strains on yields and physiological characteristics of sweet corn (Zea mays L. var saccharata) under different levels of irrigation. Three irrigation levels i.e., 100% (I100 no stress), 80% (I80), and 60% (I60) were used during sweet corn cultivation. However, there were four rhizobacteria strains i.e., P. fluorescens P1, P. fluorescens P3, P. fluorescens P8, P. fluorescens P14 which were used in the experiment. The results showed that severe water stress (60% of plant water requirement) decreased chlorophyll a, chlorophyll b, and total chlorophyll contents, Fv/Fm ratio and nutrients uptake. A significant increase in F0, Fm, proline, total soluble sugars, catalase (CAT) and peroxidase (POX) activity led to less ear yield and canned seed yield. Combination of four strains significantly increased the yield traits of sweet corn i.e., ear and (44%) and canned seed yield (27%) over control. The highest promoting effect was observed in the combination of four strains treatment and followed by P1 strain in reducing the harmful effects of drought stress and improving sweet corn productivity. However, P14 gave minimum improvement in growth and yield indices under limited availability of water. In conclusion, combination of four strains inoculation is an efficacious approach for the achievement of better yield of sweet corn under osmotic stress.

The low availability of micronutrients such as zinc (Zn) and iron (Fe) and macronutrients (phosphorus (P), in particular) in calcareous soils adversely affects plants such as sorghum (Sorghum bicolor) that are highly sensitive to deficiencies of these elements. This study investigated the potential effects of different Fe chelates and plant growth-promoting rhizobacteria (PGPR) on nutrition and growth of sorghum plants growing in a low-fertility calcareous soil. A glasshouse experiment was carried out in a completely randomized design with four PGPR treatments (Pseudomonas putida P159, Pseudomonas fluorescens T17-24, Bacillus subtilis P96, and an uninoculated control), and three Fe treatments (10 mg Fe kg −1 soil as Fe-EDDHA or Fe-EDTA, and no Fe application). Application of both Fe chelates (Fe-EDDHA and Fe-EDTA) increased plant dry weight, shoot content, and concentration of Zn and Cu (copper) compared with the control treatment; however, Fe-EDTAwas found to be more effective than Fe-EDDHA. Fe-EDTA significantly increased the concentration of Cu, Zn, and Mn (manganese) up to 74.7%, 40.3%, and 30.6% in the rhizosphere, respectively. The use of PGPR significantly increased plant growth as well as the content of Mn, Zn, Cu, and K (potassium) compared with the uninoculated plants. Overall, the Fe-EDTA chelate was more effective in increasing nutrient uptake and growth of sorghum plants than Fe-EDDHA because of its low chemical stability at high pH. Combined application of Fe-EDTA and PGPR strains provided the greatest growth and nutritional benefits to sorghum plants growing in the alkaline nutrient-deficient calcareous soil.

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In order to improve effectiveness of phosphate rock as phosphorus fertilizer, elemental sulfur and# Thiobacillus have evaluated as amendments. First, Thiobacillus were isolated from different#soil samples. Then, a greenhouse pot experiment was conducted using a completely randomized factorial#design with three factors#included: elemental sulfur at four levels of 0, 1000, 2000#and 5000 mg kgP -1 P , phosphate rock at three levels of 0, 1000 and 2000 mg kgP -1 P , four#Thiobacillus inoculums (TR 1 R, TR 2 R, TR 3 R, TR 4 R) and without inoculation (TR 0 R) in three replications.#Results showed that, all the four Thiobacillus inoculums increased significantly#extractable soil-P. Combined application of# phosphate rock and sulfur7 T 7 T in equal7 T 7 T 4 5 T proportion (14 5 T :4 5 T 14 5 T ) along with inoculum Thiobacillus had significant effect in improving phosphorus availability in soil. Combined application of sulfur (at rates of 1000 and 2000 mg kgP -1 P ) and Thiobacillus significantly increased phosphorus uptake by plants as compared to the control.