Dr. David Deamer
Department of Biomolecular Engineering – University of California, Santa Cruz
“A new model for the origin of cellular life: Coupled phases and combinatorial selection in hydrothermal pools”
The earliest emergence of cellular life was preceded by the self-assembly of protocells, which are defined as systems of functional polymers encapsulated in membranous compartments. Although the environment that fostered primitive cellular life is still largely unconstrained, we can be reasonably confident that liquid water was required, together with a source of organic compounds and energy to drive polymerization reactions. There must also have been a process by which the compounds were sufficiently concentrated to undergo physical and chemical interactions. We are exploring self-assembly processes and polymerization reactions in prebiotic analogue environments and in laboratory simulations. The analogue environments include volcanic regions in Kamchatka, Hawaii, Iceland and northern California that have hydrothermal fields characterized by geysers, hot springs and small pools undergoing cycles of hydration and dehydration. In my talk, I will discuss why we think these are relatively plausible sites when compared to proposed marine hydrothermal vents. We used nanopore analysis and other techniques to demonstrate that the fluctuating conditions of hydrothermal fields promote the synthesis of RNA-like polymers from ordered arrays of mononucleotides in multilamellar lipid structures. Chemical activation of the mononucleotides is not required. Instead, synthesis of phosphodiester bonds is driven by the chemical potential of fluctuating anhydrous and hydrated conditions, with heat providing activation energy during dehydration. In the final hydration step, the RNA is encapsulated within lipid vesicles. We propose that lipid-assisted polymerization serves as a model of an early stage of evolution toward a version of primitive cellular life that uses RNA as a catalyst and a way to store and transmit genetic information.
Dr. David Deamer
Dave Deamer grew up in Westerville, Ohio where he spent happy summer months collecting butterflies and exploring caves. He traveled south to Duke University to complete an undergraduate degree in Chemistry in 1961, then back to Ohio for a Ph. D. in physiologicalchemistry at the Ohio State University Medical School in 1965. After 2 years post-doctoral research at UC-Berkeley, he joined the biology faculty at UC Davis in 1967 where he worked on liposomes and proton transport. After a sabbatical in 1975 with Alec Bangham in England, he came up with a question that he is still working to answer: What were the first membranes, and how did they contribute to the origin of life?
In 1989, while still at UC-Davis, Deamer came up with the idea that it might be possible to sequence DNA by using voltage to draw a single strand through a nanoscopic pore embedded in a membrane. As each base passed through the pore, it would produce a base-specific modulation of ionic current that reveals the sequence of bases. He joined forces with Dan Branton at Harvard to pursue this idea, and in 1996 they published a paper in PNAS that has been cited over 2000 times. Oxford Nanopore Technology licensed the IP and in 2014 released the MinION nanopore sequencer to early users. Deamer now uses nanopore devices to analyze polymers resembling nucleic acids that are produced in simulations of hydrothermal conditions on the prebiotic Earth.
1. Black RA, Blosser MC, Stottrup BL, Tavakley R, Deamer DW, Keller SL. 2013. Nucleobases bind to and stabilize aggregates of a prebiotic amphiphile, providing a viable mechanism for the emergence of protocells. Proc Natl Acad Sci U S A. 110:13272-6.
2. Toppozini L, Dies H, Deamer DW, Rheinstädter MC. 2013. Adenosine monophosphate forms ordered arrays in multilamellar lipid matrices: insights into assembly of nucleic acid for primitive life. PLoS One. 8:e62810.
3. Georgio CD, Deamer DW. 2014. Lipids as universal biomarkers of extraterrestrial life. Astrobiology 14: 541 – 49.
4. DeGuzman V, Vercoutere W, Shenasa H, Deamer D. 2014. Generation of oligonucleotides under hydrothermal conditions by non-enzymatic polymerization. J Mol Evol. 78:251-62.
5. Da Silva L, Maurel MC, Deamer D. 2015. Salt-promoted synthesis of RNA-like molecules in simulated hydrothermal conditions. J Mol Evol. 80:86-97.
6. Damer B, Deamer D. 2015. Coupled phases and combinatorial selection in fluctuating hydrothermal pools: a scenario to