Biological Means of Arsenic Minimization with Special Reference to Siderophore

Abstract

Arsenic (As), a p-block element, is a metalloid common on earth crust in various forms such as arsenopyrite and scorodite. It is known to be present in four oxidation states that are −3, 0, +3 and +5 of which pentavalent and trivalent forms are most toxic. Arsenic in its various forms proves hazardous to environment and all living beings including microbes, animals and plants. In animals, it affects almost all vital organs including liver, kidneys, heart and lungs. As is a known carcinogen too. In plants, As triggers production of reactive oxygen species hence deteriorate development and metabolism of plants. To mitigate these hazardous effects organisms have developed As detoxification mechanisms such as arsenic transforming enzymes, phytochelatins, etc. An emerging discovery in context of arsenic mitigation is utilization of siderophores. Siderophores are secondary metabolites of microorganisms, some plants as well as mammalian cells. These are low molecular weight peptides synthesized via ribosome independent process using non-ribosomal peptide synthetase enzymes. Major function of siderophore was believed to be chelation of iron to make it accessible for siderophore producers. However, studies proved that it can too binds with other heavy metals and metalloids and form thermodynamically stable complex. The complex formation between siderophores and different metals and metalloids including As depends on various physiochemical parameters. This chapter highlights different aspects of arsenic detoxification in organisms with special reference to siderophore utilization in arsenic mitigation.