Evaluation of heavy metals tolerant bacterial strains as antioxidant agents and plant growth promoters

Abstract

Abstract This study aimed to evaluate three heavy metal tolerant bacterial strains (HMTB) namely Alcaligenes faecalis MG257493.1, Bacillus cereus MG257494.1 and Alcaligenes faecalis MG966440.1 as antioxidant agents and plant growth promotors under laboratory conditions. Their abilities to inhibit 2,2-DiPhenyl-2-Picrylhydrazyl hydrate (DPPH) as non-enzymatic antioxidant activity and produce plant growth promoters (indole acetic acid (IAA), gibberellins (GA3), salicylic acid (SA), proline (Pro.), sidrophores, exopolysaccharide (EPS) and biosurfactant) were estimated in presence of four heavy metals Zinc (Zn2+) cadmium (Cd2+), copper (Cu2+) and lead (Pb2+) at 1000 and 1500 mg/l. Results showed that the antioxidant activities of three strains were increased with the increasing of heavy metals concentration. All tested strains were able to produce all estimated plant growth promoters in the presence or absence of heavy metals and the highest amounts of all compounds were recorded in media free of heavy metals and decreased with the increasing of heavy metals concentration. Also, results proved that the three evaluated strains were considered as heavy metal tolerant-plant growth promoting bacteria (HMT-PGPB) and have beneficial characteristics for remediating the contaminated mine tailing soil.