Heavy metals can be biosorbed by microbes at binding sites present in cellular structure without the
involvement of energy. Among the various reactive compounds associated with bacterial cell walls, the
extracellular polymeric substances are of particular importance and are well known to have significant
effects on acid-base properties and metal adsorption [55]. Studies on the metal binding behavior of
extracellular polymeric substances (EPS) revealed a great ability to complex heavy metals through
various mechanisms, which include proton exchange and micro-precipitation of metals [56,57]. Recent
studies have characterized and quantified the proton and adsorbed metals on bacterial cells and EPS free
cells in order to determine the relative importance of EPS molecules in metal removal [58].
Bioremediation research and practice are still hampered in the current scenario due to an incomplete
understanding of genetics and genome level characteristics of the organisms used in metal adsorption,
the metabolic pathway and their kinetics. This results in an inability to model and predict the process
behavior and develop a natural bioremediation process in the field [29,30,32,59,60].