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6206005 
Book/Book Chapter 
Archaea 
Borrego, CM; Casamayor, EO 
2009 
Academic Press 
Oxford 
Encyclopedia of Inland Waters 
167-181 
Archaea are a common component of prokaryotic freshwater plankton, but most have been unknown to limnology until recently. Widespread methanogens and extreme archaeal halophiles and thermophiles were described long ago with their functions, roles, and distribution in inland waters well established. However, knowledge of the distribution and metabolic capabilities of archaea have increased markedly with the application of new methods. Unfortunately, cultivation has remained elusive for these new archaeal groups and no evidence on their metabolism or role within the ecosystem are available. Natural abundances for uncultured archaea are substantial, within a range 1–10% of total prokaryotic plankton and archaeal representation is even higher for certain mesophilic and psychrophilic environments. To overcome current limitations to understanding archaea, the combination of new cultivation strategies, high-resolution molecular technologies, more detailed biogeochemical approaches, traditional microbiological methods, and bioinformatic tools are being used. New metabolic capabilities of these unveiled and widespread archaea are emerging, such as the anaerobic oxidation of methane, fixation of CO2, nitrification, and denitrification. New discoveries are likely and archaea have become one of the most exciting current topics in microbial aquatic research. There is an open race to bring into culture and to understand the ecology of some of the most enigmatic microbes present in freshwater environments. 
Archaea; Chemoautotrophy; Crenarchaeota; Euryarchaeota; Extremophiles; Halophyles; Methanogens; Nitrogen cycle; Salt lakes; Stratified lakes; Oligotrophic lakes; Thermophiles; Uncultured microbes; 16S rRNA gene 
Likens, Gene E.