Microbial diversity at 83 degrees C in Calcite Springs, Yellowstone National Park: another environment where the Aquificales and "Korarchaeota" coexist

The use of molecular phylogenetic approaches in microbial ecology has revol utionized our view of microbial diversity at high temperatures and led to t he proposal of a new kingdom within the Archaea, namely, the "Korarchaeota. " We report here the occurrence of another member of this archaeal group an d a deeply rooted bacterial sequence from a thermal spring in Yellowstone N ational Park (USA). The DNA of a mixed community growing at 83 degrees C, p H 7.6, was extracted and the small subunit ribosomal RNA gene (16S rDNA) se quences were obtained using the polymerase chain reaction. The products wer e cloned and five different phylogenetic types ("phylotypes") were identifi ed: four archaeal phylotypes, designated pBA1, pBA2, pBA3, and pBA5, and on ly one bacterial phylotype, designated pBB. pBA5 is very closely related to the korarchaeotal phylotype, pJP27, from Obsidian Pool in Yellowstone Nati onal Park. The FEB phylotype is a lineage within the Aquificales and, based on 16S rRNA sequence, is different enough from the members of the Aquifica les to constitute a different genus. In situ hybridization with bacterial-s pecific and Aquificales-specific fluorescent oligonucleotide probes indicat ed the bacterial population dominated the community and most likely contrib uted significantly to biogeochemical cycling within the community.