Original Paper

Archives of Microbiology

, Volume 181, Issue 4, pp 269-277

First online:

Thermobaculum terrenum gen. nov., sp. nov.: a non-phototrophic gram-positive thermophile representing an environmental clone group related to the Chloroflexi (green non-sulfur bacteria) and Thermomicrobia

  • Lina M. BoteroAffiliated withThermal Biology Institute, Montana State University
  • , Kathy B. BrownAffiliated withThermal Biology Institute, Montana State UniversitySierra High School
  • , Sue BrumefieldAffiliated withThermal Biology Institute, Montana State University
  • , Mark BurrAffiliated withThermal Biology Institute, Montana State University
  • , Richard W. CastenholzAffiliated withCenter for Ecology and Evolutionary Biology, University of OregonNASA Aimes Research Center, NASA Astrobiology Institute
  • , Mark YoungAffiliated withThermal Biology Institute, Montana State University
  • , Timothy R. McDermottAffiliated withThermal Biology Institute, Montana State University Email author 

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access


A novel bacterium was cultivated from an extreme thermal soil in Yellowstone National Park, Wyoming, USA, that at the time of sampling had a pH of 3.9 and a temperature range of 65–92 °C. This organism was found to be an obligate aerobic, non-spore-forming rod, and formed pink-colored colonies. Phylogenetic analysis of the 16S rRNA gene sequence placed this organism in a clade composed entirely of environmental clones most closely related to the phyla Chloroflexi and Thermomicrobia. This bacterium stained gram-positive, contained a novel fatty-acid profile, had cell wall muramic acid content similar to that of Bacillus subtilis (significantly greater than Escherichia coli), and failed to display a lipopolysaccharide profile in SDS-polyacrylamide gels that would be indicative of a gram-negative cell wall structure. Ultrastructure examinations with transmission electron microscopy showed a thick cell wall (approximately 34 nm wide) external to a cytoplasmic membrane. The organism was not motile under the culture conditions used, and electron microscopic examination showed no evidence of flagella. Genomic G+C content was 56.4 mol%, and growth was optimal at 67 °C and at a pH of 7.0. This organism was able to grow heterotrophically on various carbon compounds, would use only oxygen as an electron acceptor, and its growth was not affected by light. A new species of a novel genus is proposed, with YNP1T (T=type strain) being Thermobaculum terrenum gen. nov., sp. nov. (16S rDNA gene GenBank accession AF391972). This bacterium has been deposited in the American Type Culture Collection (ATCC BAA-798) and the University of Oregon Culture Collection of Microorganisms from Extreme Environments (CCMEE 7001).


Thermophile Green non-sulfur Chloroflexi Gram-positive Yellowstone National Park Thermal soil