Isotopic fractionation autotrophic

A schematic overview of the relevant processes is shown in Figure 1. Plants and other autotrophs fix CO2. Animals and other heterotrophs utilize organic compounds. If the assimilated carbon is a small molecule (like CO2, CH4, or acetate), significant isotopic fractionation is likely to accompany the fixation or assimilation of C. Such fractionations establish the isotopic relationship between an organism and its carbon source. Those associated with photosynthesis encode information about chemical and physical conditions in the environment of fixation. Logically, therefore, they are treated here in the chapter dealing with the biogeochemistry of marine basins (Freeman, this volume). 

Strauss G, Fuchs G (1993) Enzymes of a novel autotrophic CO2 fixation pathway in the phototrophic bacterium Chloroflexus aurantiacus, the 3-hydroxypropionate cycle. Eur J Biochem 275 633-643 Summons RE, Jahnke LL, Roksandic Z (1994) Carbon isotopic fractionation in lipids from methanotrophic bacteria Relevance for interpretation of the geochemical record of biiomarkers. Geochim Cosmochim Acta 13 2853-2863... 

Table 2. Enzymatic isotope effects and overall fractionations associated with fixation of inorganic carbon during autotrophic growth.

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