Thermobaculum terrenum ATCC BAA-798

Thermobaculum terrenum (strain ATCC BAA-798 / YNP1) is an obligate aerobic, non-spore-forming, hyperthermophilic Gram-positive bacterium isolated from an extreme thermal soil (pH of 3.9 and temperatures ranging from 65 to 92 degrees Celsius) in Yellowstone National Park, Wyoming, USA. It forms pink-colored colonies. This organism is able to grow heterotrophically on various carbon compounds and at temperatures of up to 92 degrees Celsius. Growth occurs in a pH range of 6-8, the optimum being pH 7. It uses only oxygen as an electron acceptor, and its growth is not affected by light. T. terrenum contains a novel fatty acid profile, has cell wall muramic acid content similar to that of Bacillus, and fails to display a lipopolysaccharide profile in SDS-polyacrylamide gels (indicative of a Gram-negative cell wall structure). Ultrastructure examinations with transmission electron microscopy shows a thick cell wall (approximately 34 nm wide) external to a cytoplasmic membrane. 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. Perhaps the most intriguing characteristic of T.terrenum that sets it apart from Chloroflexi and its relatives is the cell wall structure, which appears to resemble that of a typical Gram-positive bacterium. The Chloroflexi all share the common trait of lacking an outer membrane; however, all members also have a very thin cell wall and stain Gram-negative. Therefore, T. terrenum likely represents an extreme example within a continuum of cell wall structures observed in the Chloroflexi-Thermomicrobia cluster. (EBI Integr8)