Ratios of carbon isotopes in microbial lipids as indicator of substrate usage

A study on the discrimination of the stable carbon isotopes by different microorganisms were made to determine whether ratios of carbon isotopes in microbial lipids can be used as indicators of substrate usage. Eleven strains of well known bacterial and fungal species with four different isotopically define carbon sources were grown and their isotope ratios of fatty acids of different lipid fractions were identified. Results show that the isotope ratio does not depend on the growth stage.