SRP007118 cDNA_SS_NG_AZ Comparative community gene expression analysis of Aquificales-dominant geothermal springs Members of Sulfurihydrogenibium are often observed as visible filamentous biomass in circumneutral terrestrial hot springs, and play roles in sulfur-cycling, hydrogen oxidation and iron mineralization. To gain insight into ecophysiology of Sulfurihydrogenibium populations in situ, we conducted meta-transcriptomic analysis of three distinct thermal springs (Calcite Springs and Mammoth Springs in Yellowstone National Park, USA, and Furnas Springs, Azores, Portugal) by pyrosequencing of cDNA libraries (~20, 4, and 4Mb, respectively).