The Diversity of Microbial Extremophiles

FARÍAS, MARÍA EUGENIA; MARIA C. RASUK; ALBARRACIN VIRGINIA H.; FERRER GABRIELA M.

Molecular Diversity of Environmental Prokaryotes

Taylor and Francis Group

Año: 2016; p. 87 - 126

Extreme environments are defined as those habitats in which human life is not possible. Thus, from a human point of view, those forms of life thriving in those conditions will be called as?extremophiles.? Environments that harbor this kind of life are widespread around the globe, including hot springs, hydrothermal vents, deep ocean, deserts, high-altitude environments, brines and soda lakes, nuclear reactors, ice sheets, and toxic wastes (Stetter 1999; Miroshnichenko and Bonch-Osmolovskaya 2006; Raymond et al. 2008; Dib et al. 2009; Albarracín et al. 2011,2012; Albarracín and Farías 2012).Including representatives of all three domains of life, that is, Bacteria, Archaea, and Eukaryote,extremophiles are denoted by a descriptive term, usually a word with Greek or Latin roots followedby the combining form phile Greek term for ?loving.? Their names are given depending on thephysicochemical factor they withstand, such as thermophiles, psychrophiles (organisms growingbest at high or low temperatures), acidophiles, alkaliphiles (organisms optimally adapted to acidicor basic pH values), barophiles (organisms that grow best under pressure), xerophiles (resistant todesiccation), or halophiles (organisms that require high salt concentrations for growth). In addition,a much larger diversity of organisms can tolerate extreme conditions and grow, but not necessarilyoptimally in extreme habitats; these organisms are defined as extremotrophs or extreme tolerant(Stojanović et al. 2008; Madigan et al. 2014).The discovery of extremophiles has drastically changed our understanding toward the diversity oflife itself and the conditions under which it can be sustained. Thus, extremophiles are of interest forboth basic and applied science. Indeed, these ?superbugs? hold many interesting biological secrets, suchas the biochemical limits on the stability of macromolecules and the genetic instructions for constructingstable macromolecules to one or another extreme. They are very important in the study of originsof life; many extremophiles, in particular the hyperthermophiles, lie close to the ?universal ancestor?of all existent life on Earth. This exciting realization has fueled much research on these organisms tounderstand the nature of primitive life forms, how the first cells ?made a living? in Earth?s early days,and how early organisms set the stage for the evolution of modern life forms (Madigan 2000). Also,astrobiologists are particularly interested in studying extremophiles, as many organisms of this typeare capable of surviving in environments similar to those from other planets; Mars may have regions inits deep subsurface that could harbor extremophiles. Likewise, the subsurface water ocean of Jupiter?smoon Europa may harbor a similar ?extreme? life (Westall et al. 2002; Edwards et al. 2005).Extremophiles are also the focus of biotechnological processes. Due to their amazing array ofenzymes and other chemical compounds, they have provided products to be used under extremeconditions in applications as diverse as laundry detergent additives and the genetic identification ofcriminals (Ito et al. 1998).The aim of this work is to offer a short, but comprehensive report on the biology and biodiversityof extremophilic microbes thriving in particular environments around the globe together with adescription on their importance for basic research and common biotechnological applications.