I am employed by NASA as a research microbiologist and have worked in the Exobiology/Astrobiology programs as a principal investigator for over 20 years. My work focuses on microbial lipid biochemistry of ecologically significant microorganisms. I am interested in the evolution of early microbial ecosystems particularly in relation to the emergence of the cyanobacteria and oxygenic photosynthesis. Studies in my laboratory identify specific lipid biomarkers and determine the effect of carbon isotopic discrimination associated with biosynthesis in support of environmental microbial community analysis and interpretation of EarthÕs ancient organic geochemical record. My work attempts to understand the influence of environmental change on the lipid composition of microorganisms, and potential deposition and preservation in sedimentary and mineralizing environments.
Current projects and interests involve: 1) biomarker analysis of marine cyanobacteria and associated microbial communities; 2) the influence of UV on cyanobacterial diversity and adaptation with emphasis on potential changes to membrane lipid composition and biomarker contribution to organic sediments; and 3) the influence of photorespiration on the carbon isotopic composition of cyanobacterial lipids and potential effects associated with carbon isotope partition within microbial communities.
Recent publications of interest:
- Summons, R.E., Bradley, A.S., Jahnke, L.L. & J.R. Waldbauer (2006) Steroids, triterpenoids and molecular oxygen. Philosophical Transactions of the Royal Society 361:951-968.
- Jahnke, L.L., Embaye, T., Hope, J., Turk, K. A., van Zuilen, M., Des Marais, D. J., Farmer, J. D., and Summons, R. E. 2004. Lipid Biomarker and Carbon Isotopic Signatures for Stromatolite-Forming, Microbial Mat Communities and Phormidium cultures from Yellowstone National Park. Geobiology 2:31-47.
- Londry, K. L., Jahnke, L.L. and Des Marais, D. J. 2004. Stable carbon isotope ratios of lipid biomarkers of sulfate-reducing bacteria. Applied and Environmental Microbiology 70:745-751.
- Jahnke, L.L., Eder, W., Huber, R., Hope, J. M., Hinrichs, K.-U., Hayes, J. M., Des Marais, D. J., Cady, S. L., and Summons, R. E. 2001. Signature lipids and stable carbon isotope analyses of Octopus Spring hyperthermophilic communities compared with those of Aquificales representatives. Applied and Environmental Microbiology 67:5179-5189.
- Beaumont, V.I., Jahnke, L.L. and Des Marais, D.J. 2000. Nitrogen isotopic fractionation in the synthesis of photosynthetic pigments in Rhodobacter capsulatus and Anabaena cylindrica Organic Geochemistry 31:1075-1085.
- Summons, R. E., Jahnke, L.L., Hope, J.M. and Logan G.A. 1999. 2-Methylhopanoids as biomarkers for cyanobacterial oxygenic photosynthesis. Nature 400:554-557.
- Jahnke, L.L., Summons, R.E., Hope, J.M., Des Marais, D.J. 1999. Carbon isotopic fractionation in lipids from methanotrophic bacteria II. The effects of physiology and environmental parameters on the biosynthesis and isotopic signatures of biomarkers. Geochim. Cosmochim Acta 63:79-93.