Postdoctoral Fellow - UW Friday Harbor Labs
rkodner at u.washington.edu
Education
Harvard University PhD, Biology, 2007
Department of Organismic and Evolutionary Biology
Thesis Advisor: Dr. Andrew Knoll
University of Wisconsin-Madison Bachelors of Science, 2000
Majors: Paleobiology with honors and History
Academic Advisor: Dr. Linda E. Graham
Overview of Research Interests
My current research is focusing on modern marine phytoplankton and using targeted metagenomics to study community production of lipid biomarkers in the environment. I will investigate sources and sinks of organic carbon from marine phytoplankton communities by studying genes for biomarker biosynthesis in the water column and characterizing lipids in the same samples. In addition, I will investigate flux of the same biomarkers to sediments using a sediment trap and sediment cores (in collaboration with Julian Sachs, UW School of Oceanography). I am focusing on phytoplankton in Puget Sound and my field area is the San Juan Islands (WA) where I am a Friday Harbor Labs Postdoctoral Fellow (http://depts.washington.edu/fhl/). This work will contribute to the growing effort to understand the biological feedback in the global carbon cycle.
Research Background
I am a geobiologist and have experience working with molecular biology, organic geochemistry and fossils. The coevolution of the biosphere and the geosphere form the foundation of my research interests and have motivated the interdisciplinary approach that I have used since I was an undergraduate. My work focuses on recognizing and interpreting evidence of life in the geologic record and using it to understand the past, present and future role that organisms play in the global carbon cycle. I use modern organisms as a platform for exploring the past recorded in microfossils and organic geochemical signatures.
My research has employed a number of techniques in combination, including comparative biochemistry, phylogenetics, genomics, micropaleonotolgy, SEM/TEM and microchemistry. My current work focuses on lipid biomarkers. Biomarkers are molecules preserved independently in the environment, thereby providing a record of organisms that may not be otherwise recognizable. These molecules can be used to describe ancient organisms and ecosystems independent of a traditional fossil record when analyzed from rocks, and can be used to track biomass in water and sediment in modern environments and the recent past. Yet biomarkers only work when restricted to a defined group of organisms. My work attempts to characterize the taxonomic specificity of common biomarkers.
Dissertation Research
I worked on a number of projects during my PhD work at Harvard University in Andy Knoll's lab (http://www.fas.harvard.edu/%7Eknollgrp/index.htm), and with Roger Summons (MIT, Department of Earth, Atmospheric, and Planetary Sciences) and Ann Pearson (Department of Earth and Planetary Sciences, Harvard University).
One of the pioneering areas of my research is using genomic data to identify genes for biomarker biosynthesis, in order to investigate taxonomic specificity and evolution of these molecules. I defined the biosynthetic potential of an organism to produce sterol biomarkers using genes from a complete genome sequence. I use this approach in a study with choanoflagellates, marine microorganisms with a sequenced genome and that hold an important phylogenetic position with respect to the origin of metazoans. The origin of metazoans is putatively marked in the geologic record by a sterol-derived biomarker, believe to be specific to demosponges. I investigated the potential of choanoflagellates to make this biomarker using genomic information. The genomic approached allowed a new way to determine the potential of biomarker production and to investigate the evolution of the biosynthetic pathway of a biomarker using phylogenomics (Kodner, et. al, PNAS, July 22, 2008).
I created a database of sterol lipids, the progenitor of one of the most common classes of lipid biomarkers, from algal groups in the kingdom Plantae. These lipids (characterized with GC-MS) were again placed within a phylogenetic framework to describe the distribution and evolutionary history of these molecules within a diverse monophyletic lineage. This analysis aids in interpreting the Paleozoic sterane record, and is currently used as evidence that green algae were dominant primary producers in ancient oceans (Kodner, et al., in press, Geobiology, August 2008).
I characterized a biopolymer thought to be a green algal biomarker (algaenan) from a diverse group of algae using pyrolysis GC-MS and put it in a phylogenetic context. This work helped to establish that algaenan, found in great abundance in the geologic record, actually has a very limited distribution among modern green algae and is not likely to be the source of the common geopolymer (Kodner, et al. in prep).
I study a unique marine green algal phytoplankton from the genus Halosphaera, which is a phycomate prasinophyte. The phycoma, a green algal reproductive structure presented as the best modern analog for the most ancient eukaryotic organic microfossils. The phycoma has long been thought to have substantial preservation potential and superficially resembles many ancient spheroidal microfossils. By this association, much of the organic walled microfossil record has been described as remains of phytoplankton. This project involved locating and field sampling this elusive structure, which remains unculturable. My SEM, TEM, and chemical analyses show limited support for the relation of spheroidal microfossils and phycoma, and support some new fossil ultrastructure data that suggest a greater diversity of organisms produce spheroidal microfossils than previously thought (Cohen, Kodner, and Knoll, in prep). This work has also called into question long standing ideas about microfossil preservation. In addition, I am describing the species I work on in Washington as a new species Halosphaera.
Publications
Kodner, R. B., Summons, R.E., Pearson, A., King, N., and Knoll A. H. 2008. Sterols in a
unicellular relative to the metazoans. PNAS, 105 (29) 9897-9920
Kodner, R. B., Summons, R.E. Pearson, A., and Knoll, A. H. 2008. A quantitative investigation ofsterols in the red and green algae from a phylogenetic perspective: Relevance for the
interpretation of geologic steranes, Geobiology, August
Graham, L. E., R. B. Kodner, M. M. Fisher, J. M. Graham, L. W. Wilcox, J. M. Hackney, J. Obst, P. C. Bilkey, D. T. Hanson, M. E. Cook. 2003. Early land plant adaptations to stress: a focus on phenolics. In The Evolution of Plant Physiology, A. R. Hemsley and I. Poole [eds.], Academic Press, London. pp. 155–170.
Redecker D, R. Kodner, L.E. Graham. 2002. Palaeoglomus grayi from the Ordovician. Mycotaxon 84: 33-37
Kodner R. B. and L.E. Graham. 2001. High-temperature, acid-hydrolyzed remains of Polytrichum (Musci, Polytrichaceae) resemble enigmatic Silurian-Devonian tubular microfossils. American Journal of Botany 88 (3): 462-466
Redecker D, R. Kodner, L.E. Graham. 2000. Glomalean fungi from the Ordovician.
Science 289: 1920-1921