Development of Methods to Measure Carbon Isotope Ratios of Bacterial Biomarkers in the Environment

Abstract

The δ¹³C value of bacterial carbon is an important parameter in microbial ecology for studying the carbon flow within a microbial community and for the identification of ecological important strains involved in the mineralization of certain carbon pools in the environment. In our study, biomarkers were isolated from bacteria from a microbial consortium derived from two chemostats and δ¹³C values were measured. Similar isotope ratios between biomarkers such as fatty acids and outer membrane protein, biomass and substrate were observed. The δ¹³C analyses of outer membrane protein F of Pseudomonas and biomarker fatty acids were combined to follow bacterial assimilation of ¹³C labelled 4-chlorocatechol. This new approach was also used in the environment where soil samples were cultivated with different ¹³C traced substrates.

The isotopic analyses of bacterial biomarkers indicated that carbons of histidine were widely incorporated into bacterial biomarkers, in contrast to 4-chlorocatechol which was less often used as a substrate. Results indicate that by isolating bacterial biomarkers and measuring their δ¹³C values, activities of microbial communities in a complex environmental sample can be determined. This new method has the potential to elucidate individual carbon sources for individual bacterial taxa in microbial ecology.

Key Words:

• Aspartic acid
• biomarker
• carbon 13
• chemostat
• 4-chlorocatechol
• 4-chlorosalicylate
• fatty acids
• gas chromatography
• isotope analysis
• mass spectrometry