ABSTRACT
This chapter provides an overview of the kind of extremophilic microorganisms found on our planet and of the environments they inhabit. The physico-chemical boundaries for life on Earth are very broad. Microbial life at high temperature may also abound deep within the crust of the Earth. Permanently cold environments are abundant on planet Earth. The search for life elsewhere in the universe and the environmental changes on Earth as a result of global warming have greatly stimulated research on the microbiology of cold ecosystems. Extremophiles are found in all three domains of life: Archaea, Bacteria, and Eukarya. The archaeal domain is particularly rich in organisms adapted to life at the extremes: high salt, high temperature, hot and acidic, hypersaline and alkaline, and more. There are also thermophilic Archaea that use sulfate as the electron acceptor for anaerobic respiration. Species of the genus Archaeoglobus have been isolated from the walls of smokers’ chimneys and from sediments or marine hydrothermal systems.
