Meeting Abstract

P2.156  Tuesday, Jan. 5  Not all Lipids are Created Equal: Differential Carbon 13 Discrimination During Lipid Biosynthesis WESSELS, F. J.*; HAHN, D. A.; University of Florida; University of Florida fwessels@ufl.edu

Stable isotopes are an important research tool in physiological ecology, where they are commonly used for diet recreation or as metabolic tracers. When an organism consumes stable isotopes that are naturally present in their diet, the isotopes can be enriched or depleted as the consumer assimilates dietary components. This difference in isotopic composition between the consumer’s tissues and diet is known as discrimination. Quantifying the contribution of multiple dietary sources to a consumer’s tissues is often accomplished by using one of a variety of mixing models, which typically requires discrimination to be estimated in the model. However, the discrimination of ¹³C has either been ignored or assumed to be relatively small in many systems. These assumptions do not hold under all circumstances, leading some authors to suggest that ¹³C discrimination is dependent on the dietary concentration of ¹³C (Caut et al. 2008). In this experiment we tested whether ¹³C discrimination depends on the dietary concentration of ¹³C in the bacterium Bacillus subtilis. We found that there is a large effect of dietary ¹³C concentration on discrimination, and have attributed this concentration-dependent discrimination to the de novo biosynthesis of lipids. We discuss our findings in the context of the potential implications for stable isotope analyses.