Meta-analysis of cultivation-independent sequence data shows that geothermal systems host an abundance of novel organisms, representing a vast unexplored phylogenetic and functional diversity among yet-uncultivated thermophiles. A number of thermophiles have recently been interrogated using metagenomic and/or single-cell genomic approaches, including members of taxonomic groups that inhabit both thermal and non-thermal environments, such as 'Acetothermia' (OP1) and 'Atribacteria' (OP9/JS1), as well as the exclusively thermophilic lineages 'Korarchaeota', 'Calescamantes' (EM19), 'Fervidibacteria' (OctSpA1-106), and 'Aigarchaeota' (HWCG-I). The 'Aigarchaeota', a sister lineage to the Thaumarchaeota, likely includes both hyperthermophiles and moderate thermophiles. They inhabit terrestrial, marine, and subsurface thermal environments and comprise at least nine genus-level lineages, several of which are globally distributed.
Bibliographical noteFunding Information:
This work was supported by NASA Exobiology grant EXO-NNX11AR78G ; U.S. National Science Foundation grant OISE 0968421 ; U.S. Department of Energy (DOE) grant DE-EE-0000716 ; and the U.S. Department of Energy Joint Genome Institute (CSP-182), a DOE Office of Science User Facility, supported under Contract No. DE-AC02-05CH11231. B.P.H. acknowledges generous support from Greg Fullmer through the UNLV Foundation. T.W.A. was supported by the Richard and Beverly Hermsen Fellowship . G.B.G. was supported by the Robert E. McNair Foundation and NSF DBI-1358896. We acknowledge Steve Quake, Paul Blainey, Jad Kanbar, and Iwijn De Vlaminck for collaboration with single-cell genomics and metagenomics and Hailiang Dong and Brandon Briggs for collaboration with metagenomics. William Inskeep and Jake Beam provided an ‘Aigarchaeota’ 16S rRNA gene sequence from Octopus Spring. Duane Moser and Scott Hamilton-Brehm provided 16S rRNA gene sequences from the Nevada National Security Site (NNSS). Scott Miller, Ken Jones, Eric Boyd, Trinity Hamilton, Dan Colman, and Cristina Takacs-Vesbach provided raw 16S rRNA gene pyrotag reads. Fengping Wang, William Brazelton, and Matthew Schrenk provided metagenomic datasets.
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