LAUSR

Abstract Untreated industrial waste affects fertility of agricultural soils. Among physical, chemical and biological methods, biological is the most efficient method to control pollution from soils affected with heavy metals. Experiments were conducted to assess role of strain MAI4 for adsorption and transformation and defense mechanism activation against metals as a mechanism of detoxification and their effect in augmenting bean growth. Strain MAI4 was identified as Pseudomonas sp. by 16 sRNA gene analysis. Maximum biosorption of metals by MAI4 was found at pH 6–8, 100–400 µg/ml and 24 h. Bioinoculant could reduce maximum amount of Cr (VI) at pH 6–8, 100–400 µg/ml and 15–35° C. Bioinoculant was able to form more biofilm under metal stress which suggested its detoxification role. Exopolysaccharides and antioxidants by strain MAI4 played a protective role against cell damage as metals could not release environmental deoxyribose nucleic acid (eDNA), superoxide and malondialdehyde (MDA). Protective role of strain MAI4 was also observed under scanning electron microscopy (SEM) and energy dispersive X- ray (EDX) spectroscopy. Strain prevented uptake of metals instead helped plants accumulate more nutrients in metal amended soil analyzed under energy dispersive X- ray (EDX) spectroscopy. Activation of defense mechanism, biosorption, biotransformation together with nutrient accumulation by strain MAI4 was responsible for growth promotion of beans.