RT Journal Article SR Electronic(1) A1 Berg, Ivan A. A1 Ramos-Vera, W. Hugo A1 Petri, Anna A1 Huber, Harald A1 Fuchs, GeorgYR 2010 T1 Study of the distribution of autotrophic CO2 fixation cycles in Crenarchaeota JF Microbiology, VO 156 IS 1 SP 256 OP 269 DO https://doi.org/10.1099/mic.0.034298-0 PB Microbiology Society, SN 1465-2080, AB Two new autotrophic carbon fixation cycles have been recently described in Crenarchaeota. The 3-hydroxypropionate/4-hydroxybutyrate cycle using acetyl-coenzyme A (CoA)/propionyl-CoA carboxylase as the carboxylating enzyme has been identified for (micro)aerobic members of the Sulfolobales. The dicarboxylate/4-hydroxybutyrate cycle using oxygen-sensitive pyruvate synthase and phosphoenolpyruvate carboxylase as carboxylating enzymes has been found in members of the anaerobic Desulfurococcales and Thermoproteales. However, Sulfolobales include anaerobic and Desulfurococcales aerobic autotrophic representatives, raising the question of which of the two cycles they use. We studied the mechanisms of autotrophic CO2 fixation in the strictly anaerobic Stygiolobus azoricus (Sulfolobales) and in the facultatively aerobic Pyrolobus fumarii (Desulfurococcales). The activities of all enzymes of the 3-hydroxypropionate/4-hydroxybutyrate cycle were found in the anaerobic S. azoricus. In contrast, the aerobic or denitrifying P. fumarii possesses all enzyme activities of the dicarboxylate/4-hydroxybutyrate cycle. We conclude that autotrophic Crenarchaeota use one of the two cycles, and that their distribution correlates with the 16S rRNA-based phylogeny of this group, rather than with the aerobic or anaerobic lifestyle., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.034298-0