Stable carbon isotope fractionations of the hyperthermophilic crenarchaeonMetallosphaera sedula

The stable carbon isotopic compositions of the inorganic carbon source, bul k cell material, and isoprenoid lipids of the hyperthermophilic crenarchaeo n Metallospaera sedula, which uses a 3-hydroxypropionate-like pathway for a utotrophic carbon fixation, have been measured. Bulk cell material was appr oximately 3 parts per thousand enriched in C-13 relative to the dissolved i norganic carbon, and 2 parts per thousand depleted in C-13 relative to isop renoid membrane lipids. The isotope data suggested that M. sedula uses main ly bicarbonate rather than CO2 as inorganic carbon source, which is in acco rdance with a 3-hydroxypropionate-like carbon fixation pathway. To the best of our knowledge this is the first report of C-13 fractionation effects of such a hyperthermophilic crenarchaeon. (C) 2001 Federation of European Mic robiological Societies. Published by Elsevier Science B.V. All rights reser ved.