Reduction of heavy metals bioaccumulation in sorghum and its rhizosphere by heavy metals-tolerant bacterial consortium

A consortium of three heavy metals tolerant-plant growth promoting bacteria (HMT-PGPB) (Bacillus cereus MG257494.1, Alcaligenes faecalis MG966440.1 and Alcaligenes faecalis MG257493.1) was tested for its beneficial effects on microbial activities in sorghum' rhizosphere (Sorghum vulgare L.). Moreover their ability to reduce heavy metals bioaccumulation in soil and plant during two successive experiments achieved in vitro and greenhouse. Firstly, the activities of HMT-PGPB consortium were estimated in vitro under mixture of four heavy metals (copper, cadmium, lead, zinc) at two concentrations (1000 and 1500 mgL(-1)), to confirm its heavy metal tolerance and plant growth promoting ability, then applied as a biofertilizer for sorghum cultivated in soil contaminated with heavy metals. In vitro results, no antagonism among the tested stains was observed and the HMT-PGPB consortium produced all estimated compounds. Greenhouse results proved that the inoculation of sorghum with HMT-PGPB consortium enhanced the microbial activities like increasing dehydrogenase activity (DHA), reduction of heavy metal bioaccumulation in roots and plants and regulate heavy metals bioaccumulation factor (BAF) in rhizosphere and plant. Moreover, the inoculation of sorghum with HMT-PGPB consortium increased the microbial activities and reduced the accumulation of heavy metals in soil, besides decrease BAF values in rhizosphere and plant. The importance of this study, is that enable us to cultivate the contaminated soils with heavy metals and not neglect large areas of such soils with reducing the environmental pollution, through the inoculation of plants by bacterial consortia, that can remove the polluting elements and at the same time stimulate plant growth.