Heavy metal toxicity and possible functional aspects of microbial diversity in heavy metal-contaminated sites

Abstract

Heavy metals have emerged out as imperious category of pollutants, showing inimical effects on both human physiology and the dynamism of terrestrial and aquatic life forms and ecosystems. Depending on their oxidation states, heavy metals can be highly reactive and, therefore, toxic to the simplest to most complex organisms. Different human-based industries including metallurgical, chrome tanning, textiles, electronic, electroplating, metal culminating, fertilizer manufacture, mining, and steel and automobile industries are persuasive sources of toxic heavy metals including cadmium (Cd), gold (Au), silver (Ag), copper (Cu), lead (Pb), chromium (Cr), mercury (Hg), uranium (U), selenium (Se), zinc (Zn), arsenic (As), and nickel (Ni). All life forms including fungi, bacteria, yeasts, plants, and animals may be affected due to toxic levels of heavy metals; however, the diversity and magnitude of toxicities may vary for different organisms. Co-occurrence of different heavy metals in an ecological community may be prime mover of significant nocuous effects of the biomass/activity and diversity of soil microbiota than those instigated by single metals at high concentrations. Remediation of heavy metal-contaminated soils is getting substantial momentum and is a perplexing task as metals cannot be degraded and the jeopardies they stance are intensified by their moxie in the environment. Microorganisms are the first entity that endures direct and indirect impacts of hazardous heavy metals. Biochemical and molecular rejoinder of soil microbial population to heavy metal-polluted environment establish a germane model for ecological studies to appraise the influence and dynamics of environmental characteristics. Several microbes have habituated and harbor potential tolerance to detoxify heavy metal-contaminated environments at cellular level different strategies through bioaccumulation, biosorption, biotransformation, etc. for ameliorating heavy metal-contaminated sites. Therefore, universally, several researchers are trapping novel microorganisms for the isolation of competent heavy metal-tolerant bacteria.