Carbonate precipitation by the thermophilic archaeon Archaeoglobus fulgidus: a model of carbon flow for an ancient microorganism

Abstract. Microbial carbonate precipitation experiments were conducted using the archaeon bacteria Archaeoglobus fulgidus to determine chemical and isotopic fractionation of organic and inorganic carbon into mineral phases. Carbonate precipitation was induced in two different experiments using A. fulgidus to determine the relative abundance of organically derived carbon incorporated into carbonate minerals as well as to define any distinct phases or patterns that could be attributed to the precipitation process. One experiment used a medium containing ¹³C-depleted organic carbon and ¹³C-enriched inorganic carbon, and the other used a ¹⁴C-labeled organic carbon source. Results indicated that 0.9–24.8% organic carbon was incorporated into carbonates precipitated by A. fulgidus and that this process was mediated primarily by pH and CO₂ emission from cells. Data showed that the carbon in the CO₂ produced from this microorganism is incorporated into carbonates and that the rate at which precipitation occurs and the dynamics of the carbonate precipitation process are strongly mediated by the specific steps involved in the biochemical process for lactate oxidation by A. fulgidus.