Carbon Isotope Fractionation by Autotrophic Bacteria with Three Different C0₂ Fixation Pathways

Abstract

D edicated to Professor A chim Trebst on the occasion o f his 60th birthdayCarbon Isotope Fractionation. Autotrophy. A cetyl-C oA Pathway, Reductive Citric Acid Cycle, Calvin Cycle Carbon isotope fractionation during autotrophic growth o f different bacteria which possess different autotrophic C 0 2 fixation pathways has been studied. 13C /l2C -R atios in the cell carbon of the follow ing bacteria were determined ( C 0 2 fixation pathway suggested or proven in paren theses): A lkaligenes eutrophus (reductive pentose phosphate cycle), D esulfobacterium autotrophicum and A cetobacterium w oodii (reductive acetyl-C oA pathway), D esulfobacter hydrogenophilus and T herm oproteus neutrophilus (reductive citric acid cycle). The A ö l3C values, which indicate the p e r m ille deviation o f the 13C content o f cell carbon from that o f the C O : used as the sole carbon source, range from -10%c (reductive citric acid cycle) over -26%c (reductive pentose phosphate cycle) to -36%c (reductive acetyl-C oA pathway). A cetate formed via the acetyl-C oA pathway by the acetogenic Acetobacterium w oodii showed a A 6 I3C = -40%c. These data are discussed in view of the different C 0 2 fixation reactions used by the bacteria and especially with regard to the isotopic com position of sedim entary carbon through time.

Lipid Biomarkers and Carbon Isotope Signatures of a Microbial ( Beggiatoa ) Mat Associated with Gas Hydrates in the Gulf of Mexico

“…Because a fractionation of ϳϪ10.7‰ exists between dissolved CO 2 and dissolved inorganic carbon (dominated by bicarbonate) at the in situ temperature (ϳ10°C) (35), the actual isotope compositions of the respired CO 2 can be as low as Ϫ38.2‰. Second, if Beggiatoa used this light CO 2 for chemoautotrophic growth, the biomass should have had a ␦ 13 C value close to or below Ϫ60‰, given the typical fractionations of 20 to 26‰ between biomass and CO 2 for autotrophs using the Calvin cycle (30,48,51,59). Our measured ␦ 13 C value of biomass (Ϫ28.6‰) was significantly higher.…”

Soil organic matter dynamics: a biological perspective derived from the use of compound‐specific isotopes studies

“…Most interestingly, this is also observed in the dark, which excludes photosynthetically active organisms like algae, so that heterotrophic CO 2 fixation is suggested (Miltner et al 2005a). Several metabolic pathways of microorganisms are known for this heterotrophic carbon uptake (Preuss et al 1989;Berg et al 2007) and might be, in consequence, a missing process for carbon uptake. For soils on sedimentary substrates, carbon stored in rocks, i.e., kerogen and bitumen (Engel and Macko 1993), and (Kramer and Gleixner 2006) carbon found in coal and char is used for growth by soil microorganisms (Petsch et al 2001;Steinbeiss et al 2009;Seifert et al 2011).…”

Chemoautotrophy in the redox transition zone of the Cariaco Basin: A significant midwater source of organic carbon production

“…Consequently, their ␦ 13 C could be Ϫ26‰ or lower in the Cariaco, where the DIC is Ϫ1‰ to Ϫ2‰ (Fry et al 1991). Preuß et al (1989) have reported even greater 13 C fractionation for non-sulfur-oxidizing autotrophic bacteria (⌬␦ 13 C of Ϫ26.1‰ to Ϫ39.7‰, depending on the DIC fixation pathway). Although isotopic signatures of anaerobic, chemolithotrophic bacteria are unknown, it seems likely that chemoautotrophic production in the RTZ will be isotopically light and that the isotopic signature of bacterivorous organisms will be even more depleted in 13 C and 15 N (Ruby et al 1987).…”