Challenges and Adaptations of Life in Alkaline Habitats.

A vast array of organisms is known thriving in high pH environments. The biotechnological, medical, and environmental importance of this remarkable group of organisms has attracted a great deal of interest among researchers and industrialists. One of the most intriguing phenomena of alkaliphiles that engrossed researchers' attention is their adaptation to high pH and ability to thrive in the "extreme" condition which is often lethal to other organisms. Studies made in this line revealed that alkaliphiles deployed a range of adaptive strategies to overcome the various challenges of life in high pH environments. This chapter highlights some of the challenges and the most important structural and functional adaptations that alkaliphiles evolved to circumvent the hurdles and flourish in alkaline habitats. The fascinating alkaliphiles' pH homeostasis that effectively maintains a lower cytoplasmic pH than its extracellular environment and the remarkable bioenergetics that produce ATP much faster than non-alkaliphiles systems are reviewed in detail. Moreover, the adaptive mechanisms that alkaliphiles employ to keep the structural and functional integrity of their biomolecules at elevated pH are assessed.It is undeniable that our understanding of alkaliphiles adaptation mechanisms to high pH is expanding with time. However, considering that little is known so far about the adaptation of life in alkaline milieu, it seems that this is just the beginning. Probably, there is a lot more waiting for discovery, and some of these issues are raised in the chapter, which not only summarizes the relevant literature but also forwards new insights regarding high pH adaptation. Moreover, an effort is made to include the largely neglected eukaryotic organisms' adaptation to high pH habitats.