Geobiological Approaches to Understanding Pulmonary Infections in situ: Determining Isotopic Incorporation Rates for Growth Rate Measurements of Cystic Fibrosis Pathogens
Authors:Yang Hu, Sebastian Kopf
Mentor:Dianne Newman, Professor of the Divisions of Biology and Geological and Planetary Sciences, California Institute of Technology
Recent efforts in the Newman lab have focused on the application of geomicrobiological approaches to the in situ study of the microbial community in CF patients’ lungs. Part of this effort is the development of a stable isotope labeling technique to measure the incorporation of 2H (deuterium) from H2O into fatty acid side chains of membrane lipids as a proxy for microbial growth. In order to quantify growth rates from deuterium incorporation for a given microorganism, the rate of hydrogen incorporation from water into lipids (the water incorporation factor) must be determined. Using a synthetic cystic fibrosis growth medium and gas chromatography and isotope ratio mass spectrometry, I determined the lipid profiles and water incorporation factors of three major pathogens found in pulmonary infections of cystic fibrosis patients. These results were compared with previously obtained data from Escherichia coli, revealing a noticeable difference between the two constant factors.