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Tori Hoehler has a background in chemistry and oceanography. He now studies the interaction of microbial communities with their environment, with an emphasis on the habitability of environments beyond Earth and the detectability of any life that may reside there. He is the founding co-director of ARC's Center for Life Detection, a Fellow of the California Academy of Sciences and a Kavli Frontiers of Science Fellow, and recipient of the NASA Exceptional Scientific Achievement medal. +
Whether we are thinking about the Origin of Life, about the Molecular mechanisms of Viral Pathogenesis, or about RNA-based therapeutics, three kinds of questions underly our work: 1) What can nucleic acids do? 2) How do their sequences and structures relate to their ability to do it? and 3) Can we engineer new biologies by expressing artificial RNAs in cells? Most of the RNA and ssDNA molecules we work with are isolated using the technology of in vitro directed molecular evolution (SELEX, Systematic Evolution of Ligands by EXponential enrichment). The SELEX technology recovers rare functional molecules - for almost any function - from exceedingly complex mixtures, allowing us to explore the chemical and biological limits of what RNA and DNA can do. (Click here for a tutorial on SELEX.) +
Zach studies two of the major transitions in the history of life as a scientist in the Lunar and Planetary Laboratory at UA: the origins of replicating molecules and the origins of the eukaryotic cell. <span>His research into the origins of life is focused on geologic settings that could have promoted the synthesis of complex organic compounds on the early Earth, specifically conditions capable of driving prebiotic oligomer synthesis reactions. Zach and his collaborators at ELSI have uncovered a 'switching network' of compound synthesis driven by the radiolysis of water that selectively produces the key precursors required for abiotic ribonucleotide synthesis:</span> <span>1) Nucleobase precursor and polymer-promoting solvent formamide (Adam et al., 2018)</span> <span>2) Sugar precursors glycolaldehyde, glyceraldehyde and 2-aminooxazole (Yi et al., 2018)</span> <span>3) Polyphosphate precursor monoammonium phosphate (Adam and Lago, in prep.)</span> <span>4) Nucleotide assembly compounds, condensing agents and leaving agents such as cyanamide and cyanogen (Yi et al., 2018; Fahrenbach et al., in prep.; Adam et al., in prep.)</span> Zach also discovered two new sources of microfossils in the 1.4 billion year old Belt Supergroup of Montana. The assemblages include unique specimens of Tappania plana, one of the earliest examples of complex eukaryotes and the first such fossils reported from Laurentia. The quality of preservation, diversity of the assemblages and the accessibility of the units opens new avenues into exploring the morphology and ecology of some of Earth s oldest eukaryotes. Zach continues to study these and other fossils, looking for taxon-specific carbon isotope values and ultrastructural clues as to the affinity or metabolism of these organisms. +