Potentials of multi metal loid resistant bacteria in bioremediation and plant growth promotion

Abstract

Soil and water contamination with toxic metal(loid)s (TMs) increased globally in the newlinepresent era due to rapid industrialization, improper waste disposal, application of chemical newlinefertilizer and pesticides, mining and anthropogenic activities. Most of them are toxic even newlineat low concentrations, persistent in the environment, and cannot be degraded easily through newlinebiological, physical and chemical means to an innocuous by-product. Consequently, TMs newlineare difficult to remove from the environment, which poses threats to all life forms including newlinehumans. On the other hand, some TMs are known to play vital roles in metabolic processes newlineof microorganisms either directly or indirectly. Since microorganisms present in the field newlinecontaminated with TMs are continuously exposed to metal(loid)s stress condition, they can newlineover time develop adaptation and resistance mechanisms to those TMs. For plants, TMs newlinesuch as Cu, Zn and Ni are essential micronutrients, but are toxic to plants at high newlineconcentrations. Plants are sometimes exposed to non-essential TMs, including Hg, Cd, Pb newlineand As. Toxic effects are often associated with a delay in germination, disruption of newlinemitosis, inhibition of the enzymatic activity, retardation of root growth, induction of newlinechlorosis and reduction in the intensity of photosynthesis and respiration. Metal(loid)s newlinestress in plants may be alleviated through some plant-bacterial interactions. Bacteria that newlineexhibit resistance properties against metal(loid)s have the inherent ability to grow in high newlineconcentrations of those metal(loid)s in contaminated environment. newline