Bacterial chemolithotrophy is one of the most ancient metabolisms and is
generally defined as the ability of some microorganisms to utilize a wide range of
inorganic substrates as an energy or electron source. While lithotrophy can itself be
considered as extremophily, as only some microorganisms (the rock-eaters) have the
ability to utilize diverse inorganic chemicals as the sole source of energy, the
phylogenetically diverse groups of lithotrophs can thrive in a wide range of extreme
habitats. Apart from their excellent eco-physiological adaptability, they also possess
versatile enzymatic machinery for maintaining their lithotrophic attributes under such
extreme environments. In this chapter, we have highlighted the diversity of iron,
hydrogen and sulfur lithotrophic extremophilic bacteria in various extreme habitats,
and their role in maintaining the primary productivity, ecosystem stability and mineral
cycling / mineralogical transformations. Moreover, genetic determinants and different
enzymatic systems which are reported to be involved in such lithotrophic metabolism
also have been discussed. We hope this article will shed some new light on the field of
extremophile lithotrophy, which will eventually improve our understanding of the
extended new boundaries of life.
Keywords: Diversity of lithotrophs, Extremophilic bacteria, Hydrogen-oxidation, Iron-oxidation, Lithotrophy, Lithotrophy mechanism, Sulfur-oxidation.
