Physiological and Metabolic Basis of Microbial Adaptations Under Extreme Environments

Abstract

Microorganisms are known to inhabit domains which lie outside the perceived boundaries of life. These organisms, known as extremophiles, not only adapt to severe environmental conditions, but also often require such extreme conditions for growth and survival. These include the thermophiles (high temperature loving microorganisms), psychrophiles (low temperature loving microorganisms), acidophiles (acid loving microorganisms), alkaliphiles (alkali loving microorganisms), halophiles (salt loving microorganisms) and barophiles or piezophiles (high pressure loving microorganisms). To enable their viability in regions which are ‘empty’ in a biological sense, these organisms possess unique physiological and metabolic specialties, allowing necessary adjustments. Microbial response to physico-chemical environmental parameters like ambient temperature, pH and salinity of the medium, atmospheric pressure etc. are manifested through physiological and biochemical modifications of the cell organelles, proteins, nucleic acids, and the resultant cellular changes. Besides the intrinsic physiological stability, an overall shift in metabolic pathways, with predominance of secondary and intermediate pathways that detour the central metabolism, also provides the extremophiles with functional stability under diverse conditions. These properties have attracted research on their molecular machinery which has unveiled novel biomolecules with immense biotechnological potential. This chapter offers an insight into the ‘extremophilic’ nature of microorganisms and comprehends the adaptive strategies that these fascinating microorganisms manifest in order to be able to survive under extreme limits of environmental factors.