Beneficial role of Burkholderia cepacia in heavy metal bioremediation in metal-polluted soils and enhance the tomato plant growth

Plant rhizospheric microbes have good potential for tolerating the stress environment. In such, heavy metal tolerating soil bacteria were isolated from the tomato plant rhizosphere. The isolated bacterial strain was molecularly (16S rRNA) identified as Burkholderia cepacia. The B. cepacia showed many kinds of characteristics such as, phosphate solubilization at the range of 337.4 mu g ml-1 in broth medium; metal resistance effect up to 4 mM; solubilization of Cd and Pb at 3319 and 1170.6 mu g l-1; and also produced plant growth regulators such as HCN, siderophores, and IAA. Furthermore, the B. cepacia exhibited antifungal activity against the phytopathogenic fungi, Rhizoctonia solani (7.8 mm) and Fusarium oxysporum (6.5 mm) by significantly inhibiting fungal development. The Germination experiments indicate that when compared to control, B. cepacia-treated seeds showed the maximum level of germination within 4 days (MGT - 3.02). The bacterial strain B. cepacia with different concentrations of cadmium (Cd) and lead (Pb) metaltreated seeds increases the germination rate compared to un-inoculated metal treatments (46 % Cd, 48 % Pb). In the pot experiment, the soil application of bacterial inoculation significantly increases plant height (146.2 cm), and biomass (278 g FW). B. cepacia also induces enzyme activities such as peroxidase (PO), polyphenol oxidase (PPO), beta-1,3-glucanase, and phenols in plants with various concentrations of Cd and Pb. The present study suggests that B. cepacia partially decreased the Cd and Pb toxicity in soils and controlled phytopathogens on tomato plants by integrating numerous pathways that improved the plant response.