ABSTRACT
Halophilic microorganism, operationally defined here as those microorganisms that grow optimally at salt concentrations exceeding those of seawater (35 g/L total salts) and are able to grow at concentrations above 100 g/L, are found in all three domains of life: Archaea, Bacteria, and Eucarya. In each domain, we even find organisms that can grow in saturated brines (total salt concentrations 300-350 g/L). The physiological diversity among the halophiles is as great as their phylogenetic diversity: There are halophiles with nearly every type of metabolism known from freshwater organisms. In addition, many halophiles are adapted not only to the presence of high salt but also to other environmental extremes such as high and low temperatures and/or high pH (Oren, 2002a; Oren, 2013; Ventosa et al., 1998).
