Bacillus xiamenensis and earthworm Eisenia fetida in bio removal of lead, nickel and cadmium: A combined bioremediation approach

Heavy metals like lead (Pb), nickel (Ni), and cadmium (Cd) have a devastating effect on the environment and are harmful to humans, animals and plants. The present study was aimed at removal of heavy metals using the heavy metal (HM) resistant bacteria in combination with earthworm. The earthworms were released in Pb, Ni and Cd contaminated soil bio augmented with the potent bacterial strain (VITMSJ3) capable of taking up heavy metals. A considerable increase of 65-70% Pb, Ni and Cd by earthworm's bio augmented with VITMSJ3 was achieved without any tissue disruption. This was similarly reflected in increased enzymatic activities and reduced DNA damage in earthworms under stress conditions confirmed with COMET analysis. The presence of bacterial isolate in the earthworm gut was confirmed with scanning electron microscopy (SEM) analysis and the presence of heavy metal was evaluated and confirmed with EDAX. The study thus presents the role of a bacterial strain in the accumulation of Pb, Ni, and Cd while not only ameliorating the harmful effect of heavy metals on earthworm, but also promoting its overall physiological status.