Microbes as a boon for the bane of heavy metals

Abstract

Modern globalisation has escalated anthropocentric sources for heavy metal contamination in diverse natural habitats. Pernicious nature of heavy metals poses a major threat to all life forms in the environment. Heavy metals are not degradable like the organic pollutants but could be transformed to be persistent in a less toxic form. Microbes are the cheap tool as they evolve rapidly to combat heavy metal stress by developing various survival strategies, for instance sequestration or active transportation of metal. Their short generation time, large surface area and ease of genetic manipulation makes them ideal candidates to use for the bioremediation process. Many heavy metal resistant microbes such as species of Bacillus, Pseudomonas, Acidothiobacillus, Saccharomyces, Geobacter and Rhizophus have been used for remediation of heavy metal contaminated sites. The effectiveness of bioremediation technique depends upon various factors, including biotic as well as abiotic, which mainly determine bio-availability of metal for remediation. The different metal microbe interactions such as sorption, accumulation, mineralization, transformation and solubilization are responsible for tapering heavy metal concentration at various loci or sites. The review emphasizes on the different interactions of the microbes with heavy metals, their survival strategies and the applications of the resistant strains in remediation.