Survival Strategies and Stress Adaptations in Halophilic Archaebacteria
Anita Saini, Anil Kumar, Gulab Singh, Shiv Kumar Giri
Abstract
Throughout evolution, living organisms, including microorganisms, have developed survival strategies to live in harsh environmental conditions. The unfavorable environmental conditions may include changes in temperature, pH, oxygen, salt levels, exposure to harmful radiations and chemicals, etc. The effect of these factors has become more pronounced in the past few decades due to rapid climatic changes on the earth. The fluctuations in weather and extreme conditions have a significant impact on cellular physiology. The organisms have evolved mechanisms to protect their DNA, proteins and other cellular components essential for their survival and growth. The adaptability of microbes to changing environments accounts for their ecological preferences among different ecosystems. Among different organisms, halophilic archaebacteria from the Euryarchaeal clade, inhabiting highly saline ecological niches, are major representatives of extremophiles in nature that are very interesting from the biotechnological perspective. These microbes are exposed to different types of stresses, including fluctuations in salinity, temperature, high ionic stress, alkaline pH, exposure to radiations, metals, toxins, etc in their natural habitats and have evolved to thrive in a hostile environment. The mechanisms for their survival and adaptations in response to many stressors are largely unknown. Several strategies, however, are well understood. This chapter gives an overview of protective mechanisms in haloarchaea that account for their adaptability to natural habitats. The discussion is not limited to the compositional, architectural, and physiological aspects only. The role of genes, their expression and regulation elucidated based on genomic, proteomic and computational analysis has also been included.