. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 364 E. F. DELONG ET AL. Law6 Law1 Archaea Cenarchaeum SBAR5 Sulfolobus Desulfurococcus Pyrodictium Thermofilum Thermoproteus Pyrobaculum Halobacterium -Methanosarclna rMethanobrevibacter _Archaeoglobus ' Thermoplasma Bacteria Thermotoga Thermus. Eucarya Escherichia Variomorpha Euglena Trvpanosoma Homo sapiens Zeamays Oxytricha nova Figure 1. Tree of life inferred from 16S rRNA gene sequences showing the phylogenelic position of Cenarchaeum symbiosiim. In addition to C. symbiosum. low-temperature, uncultivated crenarchaeotes
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 364 E. F. DELONG ET AL. Law6 Law1 Archaea Cenarchaeum SBAR5 Sulfolobus Desulfurococcus Pyrodictium Thermofilum Thermoproteus Pyrobaculum Halobacterium -Methanosarclna rMethanobrevibacter _Archaeoglobus ' Thermoplasma Bacteria Thermotoga Thermus. Eucarya Escherichia Variomorpha Euglena Trvpanosoma Homo sapiens Zeamays Oxytricha nova Figure 1. Tree of life inferred from 16S rRNA gene sequences showing the phylogenelic position of Cenarchaeum symbiosiim. In addition to C. symbiosum. low-temperature, uncultivated crenarchaeotes are represented by the lineages SBAR5, 4B7. Law6. Law]. pSL12 is a cloned 16S rRNA gene fragment re- covered from a Yellowstone hot spring microorganism, and is specifically related to the iionthermophilic Crenarchaeota (4). Crenarchaeotes apparently originated in hot environments, as suggested by recent molecular ecological surveys of Archaea in hot springs (4). Ribosomal RNA clones obtained from Yellowstone hot springs (, pSL12, Fig. 1; (1. 4)) are specifically affiliated with, but basal in phylogenetic trees to, the nonthermophilic crenarchaeotes (SBAR5. 4B7, Lawl, Law6, Fig. 1; (3)). These data suggest that one or more specific lineages of hyperthermophilic crenarchaeotes adaptively radiated into colder habitats, giving rise to con- temporary nonthennophilic Crenarchaeota. Despite the in- tensive efforts of several investigators, nonthermophilic cre- narchaeotes have resisted isolation and cultivation. The physiological, biochemical, and genetic properties of this abundant, ubiquitous, and potentially biogeochemically significant group remain unknown. We recently discovered and began preliminary work on a tractable system aimed at whole genome sequencing of an uncultivated psychrophilic crenarchaeote. Specifically, high densities of a single species of psychrophilic, symbiotic crenarchaeon, Cenarchaeum symbiosum, were discovered within the tissues of its host, the marin
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
