This work was supported by a NASA Graduate Student Researcher’s Program fellowship (NGT 2-52233) to C.E.B. This work was also supported by two grants to S.L.C. (NASA-NAG5-9579 and NSF-EAR-9809471). This research was funded in part by a LExEn grant from the NSF and the NASA Astrobiology Institute to N.R.P.
Applied and Environmental Microbiology
Hot springs -- Yellowstone National Park, Thermophilic microorganisms -- Yellowstone National Park, Thermophilic microorganisms -- Morphology
The extent of hyperthermophilic microbial diversity associated with siliceous sinter (geyserite) was characterized in seven near-boiling silica-depositing springs throughout Yellowstone National Park using environmental PCR amplification of small-subunit rRNA genes (SSU rDNA), large-subunit rDNA, and the internal transcribed spacer (ITS). We found that Thermocrinis ruber, a member of the order Aquificales, is ubiquitous, an indication that primary production in these springs is driven by hydrogen oxidation. Several other lineages with no known close relatives were identified that branch among the hyperthermophilic bacteria. Although they all branch deep in the bacterial tree, the precise phylogenetic placement of many of these lineages is unresolved at this time. While some springs contained a fair amount of phylogenetic diversity, others did not. Within the same spring, communities in the subaqueous environment were not appreciably different than those in the splash zone at the edge of the pool, although a greater number of phylotypes was found along the pool?s edge. Also, microbial community composition appeared to have little correlation with the type of sinter morphology. The number of cell morphotypes identified by fluorescence in situ hybridization and scanning electron microscopy was greater than the number of phylotypes in SSU clone libraries. Despite little variation in Thermocrinis ruber SSU sequences, abundant variation was found in the hypervariable ITS region. The distribution of ITS sequence types appeared to be correlated with distinct morphotypes of Thermocrinis ruber in different pools. Therefore, species- or subspecies-level divergences are present but not detectable in highly conserved SSU sequences.
Blank, C.E., Cady, S.L. & Pace, N.R. (2002). Microbial Composition of Near-Boiling Silica-Depositing Thermal Springs Throughout Yellowstone National Park. Applied and Environmental Microbiology, 68(10), pgs 5123-5135