The use of molecular phylogenetic approaches in
microbial ecology has revolutionized our view of microbial
diversity at high temperatures and led to the proposal of
a new kingdom within the Archaea, namely, the "Korarchaeota."
We report here the occurrence of another member
of this archaeal group and a deeply rooted bacterial sequence
from a thermal spring in Yellowstone National Park
(USA). The DNA of a mixed community growing at 83°C,
pH 7.6, was extracted and the small subunit ribosomal RNA
gene (16S rDNA) sequences were obtained using the polymerase
chain reaction. The products were cloned and five
different phylogenetic types ("phylotypes") were identified:
four archaeal phylotypes, designated pBA1, pBA2, pBA3,
and pBA5, and only one bacterial phylotype, designated
pBB. pBA5 is very closely related to the korarchaeotal
phylotype, pJP27, from Obsidian Pool in Yellowstone National
Park. The pBB phylotype is a lineage within the
Aquificales and, based on 16S rRNA sequence, is different
enough from the members of the Aquificales to constitute a
different genus. In situ hybridization with bacterial-specific
and Aquificales-specific fluorescent oligonucleotide probes
indicated the bacterial population dominated the community
and most likely contributed significantly to biogeochemical
cycling within the community.
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