Chapter 19 - Role of biological macromolecules of microbes in metal bioremediation

Abstract

Microbes share a long history with heavy metals. The microbial ancestors deduced the use of metals for catalyzing energy generation and the formation of cellular components. As a result, metals were incorporated into various cellular macromolecules and became integral to the functioning of such macromolecules. Microbes utilized some metals relevant to their physiology while developed mechanisms to defend against toxic metals. Anthropogenic activities in the last few decades have released heavy metals into the environment in bioavailable forms. Microbes are known to respond immediately to the environmental changes thereby employing a host of processes like efflux, immobilization, translocation, transformation, biosorption, and bioaccumulation to alleviate metal toxicity. Biological macromolecules in microbes like carbohydrates, proteins, and nucleic acids contribute immensely toward metal bioremediation. This chapter discusses the imperative roles exhibited by microbial macromolecules in the transformation/reduction of metal toxicity in the environment. Extracellular polymeric substances comprising of polysaccharides that represent carbohydrates, various proteins like metallothioneins, metal-binding peptides, metal effluxing PIB ATPases, several enzymes important for alleviating metal-induced oxidative stress or precipitating metals have been highlighted here in the context of metal detoxification or remediation. Metal detection is the first step toward any remediation process. In recent times, there has been a great emphasis on developing functional nucleic acids-based sensors for the detection of heavy metal ions. In this regard, aptamers, DNAzymes, metal ion-specific DNAs, G-quadruplexes, and riboswitches have been detailed in this chapter. Overall, the information augments our understanding of the essential interactions of microbial macromolecules with the metals which are useful for metal remediation applications.