Bioremediation of metal contaminated sites by naturally growing lichens found in hilly areas of Himachal Pradesh

Lichen has a remarkable property of absorbing inorganic cations from the natural substrates on which they grow in amounts which are in excess of any expected requirements. We examined 20 sexicolous lichens which are known to fix metal ions found in Hilly areas of Himachal Pradesh of India for their metal fixation property. The mechanism by which Lichens take up cations is of considerable interest. Touminen (1967) proposed that alkali and alkaline metal ion uptake involved a simple ion-exchange process, which can occur inside the thallus cells of lichen by Intracellular ion-exchange mechanism of the proteins metallothioneins. Out of 20 protein samples 16 samples were found to have bound metal ions in considerable amount. These results enabled us to conclude about a similar mechanism of metal fixation in nearly all lichenic species possessing this property.