Functional characterization and alleviation of cadmium stress by endophytic bacteria isolated from Cynodon dactylon (L.) Pers․

Cadmium (Cd) contamination threatens worldwide health and environment. The Cd toxicity of soils enters in the food chains that affect plants and human health via bioaccumulation. In the present study, 20 endophytic bacterial strains were isolated from Cynodon dactylon. Out of 20 bacterial isolates exhibited plant growth-promoting attributes (PGP) such as phosphate solubilization (15 isolates), siderophore production (17 isolates), nitrogen fixation (15 isolates), Indole acetic acid (IAA) (16 isolates), ammonia production (17 isolates), extracellular enzyme activities like amylase (19 isolates), lipase (15 isolates), protease (17 isolates), and cellulase (10 isolates). Among 20 bacterial isolates, CDR5 (4.6 µg mL -1 IAA), CDR1 (19.9 µg mL -1 phosphate solubilization), CDS3 (120.7 µg mL -1 Ammonia), and CDR2 (84% siderophore) were showed highest quantitative PGP activity. The screened bacterial isolates exhibited different level of Cd tolerance in synthetic culture media. Among them, Agrobacterium CDR9 removed 33% of Cd within 72 h from a growing medium with an initial metal content of 80 mg L -1 . In vitro study reveals that CDR9 produced extracellular polymeric substances (EPS) that was confirmed by FTIR. FTIR data showed the presence of functional groups, including amine (-NH 2 ) and hydroxyl (-OH), which are active in metal ion binding. The CDR9 bacterium increased seed germination, seedling length and total biomass as compared to control under different Cd stress in Setaria italica and the significant difference in p-value (p<0.05). This study presents bacterium increases early developmental stages in plant suggesting that new insight on Cd tolerance in plant.