Life Sciences Commons^™

Sensitivity Analysis Of An Agent-Based Simulation Model Using Reconstructability Analysis, Andey M. Nunes, Martin Zwick, Wayne Wakeland

Systems Science Faculty Publications and Presentations

Reconstructability analysis, a methodology based on information theory and graph theory, was used to perform a sensitivity analysis of an agent-based model. The NetLogo BehaviorSpace tool was employed to do a full 2^k factorial parameter sweep on Uri Wilensky’s Wealth Distribution NetLogo model, to which a Gini-coefficient convergence condition was added. The analysis identified the most influential predictors (parameters and their interactions) of the Gini coefficient wealth inequality outcome. Implications of this type of analysis for building and testing agent-based simulation models are discussed.

Control Of Blood Volume Following Hypovolemic Challenge In Vertebrates: Transcapillary Versus Lymphatic Mechanisms., Stanley S. Hillman, Robert C. Drewes, Michael S. Hedrick

Biology Faculty Publications and Presentations

Anurans have an exceptional capacity for maintaining vascular volume compared with other groups of vertebrates. They can mobilize interstitial fluids via lymphatic return at rates that are ten-fold higher than mammals. This extraordinary capacity is the result of coordination of specialized skeletal muscles and pulmonary ventilation that vary volume and pressure of subcutaneous lymph sacs, thus moving lymph to dorsally located lymph hearts that return lymph to the vascular space. Variation in the capacity to mobilize lymph within anurans varies with the degree of terrestriality, development of skeletal muscles, lung volume and lung compliance, and lymph heart pressure development. This …

Pathology Findings And Correlation With Body Condition Index In Stranded Killer Whales (Orcinus Orca) In The Northeastern Pacific And Hawaii From 2004 To 2013, Stephen A. Raverty, Judy St. Leger, Dawn P. Noren, Kathy Burek Huntington, David S. Rotstein, Francis M.D. Gulland,, Deborah A. Duffield, Multiple Additional Authors

Biology Faculty Publications and Presentations

Understanding health and mortality in killer whales (Orcinus orca) is crucial for management and conservation actions. We reviewed pathology reports from 53 animals that stranded in the eastern Pacific Ocean and Hawaii between 2004 and 2013 and used data from 35 animals that stranded from 2001 to 2017 to assess association with morphometrics, blubber thickness, body condition and cause of death. Of the 53 cases, cause of death was determined for 22 (42%) and nine additional animals demonstrated findings of significant importance for population health. Causes of calf mortalities included infectious disease, nutritional, and congenital malformations. Mortalities in sub-adults were …

Projected Impact Of Mid-21st Century Climate Change On Wildfire Hazard In A Major Urban Watershed Outside Portland, Oregon Usa, Andy Mcevoy, Max Nielsen-Pincus, Andres Holz, Arielle J. Catalano, Kelly E. Gleason

Environmental Science and Management Faculty Publications and Presentations

Characterizing wildfire regimes where wildfires are uncommon is challenged by a lack of empirical information. Moreover, climate change is projected to lead to increasingly frequent wildfires and additional annual area burned in forests historically characterized by long fire return intervals. Western Oregon and Washington, USA (westside) have experienced few large wildfires (fires greater than 100 hectares) the past century and are characterized to infrequent large fires with return intervals greater than 500 years. We evaluated impacts of climate change on wildfire hazard in a major urban watershed outside Portland, OR, USA. We simulated wildfire occurrence and fire regime characteristics under …

Editor's Choice: Aldo Leopold Conservation Award, Luis A. Ruedas

Biology Faculty Publications and Presentations

Every year since 2003, the American Society of Mammalogists confers during its annual meeting the Aldo Leopold Conservation Award on a highly deserving individual. A consequence of the award for the awardee is the responsibility to write a feature article in the pages of this journal. Aldo Leopold, the namesake of the award, is considered by an overwhelming majority of biologists to be the father of contemporary conservation biology. Born in Burlington, Iowa, Leopold graduated with a Master’s degree from the Yale Forest School, which had been endowed in 1902 by the Pinchot family and was one of the first …

Novel Small Rnas Expressed By Bartonella Bacilliformis Under Multiple Conditions Reveal Potential Mechanisms For Persistence In The Sand Fly Vector And Human Host, Shaun Wachter, Linda D. Hicks, Rahul Raghavan, Michael F. Minnick

Biology Faculty Publications and Presentations

Bartonella bacilliformis, the etiological agent of Carrión’s disease, is a Gram-negative, facultative intracellular alphaproteobacterium. Carrión’s disease is an emerging but neglected tropical illness endemic to Peru, Colombia, and Ecuador. B. bacilliformis is spread between humans through the bite of female phlebotomine sand flies. As a result, the pathogen encounters significant and repeated environmental shifts during its life cycle, including changes in pH and temperature. In most bacteria, small non-coding RNAs (sRNAs) serve as effectors that may post-transcriptionally regulate the stress response to such changes. However, sRNAs have not been characterized in B. bacilliformis, to date. We …

Direct Binding Of Tfeα Opens Dna Binding Cleft Of Rna Polymeras, Sung-Hoon Jun, Jaekyung Hyun, Hoyoung Kim, Michael S. Bartlett, Hyun-Soo Cho, Katsuhiko S. Murakami

Biology Faculty Publications and Presentations

Opening of the DNA binding cleft of cellular RNA polymerase (RNAP) is necessary for transcription initiation but the underlying molecular mechanism is not known. Here, we report on the cryo-electron microscopy structures of the RNAP, RNAP-TFEα binary, and RNAPTFEα-promoter DNA ternary complexes from archaea, Thermococcus kodakarensis (Tko). The structures reveal that TFEα bridges the RNAP clamp and stalk domains to open the DNA binding cleft. Positioning of promoter DNA into the cleft closes it while maintaining the TFEα interactions with the RNAP mobile modules. The structures and photo-crosslinking results also suggest that the conserved aromatic residue in the extended winged-helix …

Landscape Genetics Of Plants: Challenges And Opportunities, Mitchell Cruzan, Elizabeth C. Hendrickson

Biology Faculty Publications and Presentations

Dispersal is one of the most important but least understood processes in plant ecology and evolutionary biology. Dispersal of seeds maintains and establishes populations, and pollen and seed dispersal are responsible for gene flow within and among populations. Traditional views of dispersal and gene flow assume models that are governed solely by geographic distance and do not account for variation in dispersal vector behavior in response to heterogenous landscapes. Landscape genetics integrates population genetics with Geographic Information Systems (GIS) to evaluate the effects of landscape features on gene flow patterns (effective dispersal). Surprisingly, relatively few landscape genetic studies have been …

Gaba Metabolism Is Crucial For Long-Term Survival Of Anoxia In Annual Killifish Embryos, Daniel E. Zajic, Jason Podrabsky

Biology Faculty Publications and Presentations

In most vertebrates, a lack of oxygen quickly leads to irreparable damages to vital organs, such as the brain and heart. However, there are some vertebrates that have evolved mechanisms to survive periods of no oxygen (anoxia). The annual killifish (Austrofundulus limnaeus) survives in ephemeral ponds in the coastal deserts of Venezuela and their embryos have the remarkable ability to tolerate anoxia for months. When exposed to anoxia, embryos of A. limnaeus respond by producing significant amounts of γ-aminobutyric acid (GABA). This study aims to understand the role of GABA in supporting the metabolic response to anoxia. To explore this, …

A Rapid Caspase-11 Response Induced By Ifng Priming Is Independent Of Guanylate Binding Proteins, Sky W. Brubaker, Susan M. Brewer, Liliana M. Massis, Brooke A. Napier, Denise M. Monack

Biology Faculty Publications and Presentations

In mammalian cells, inflammatory caspases detect Gram-negative bacterial invasion by binding lipopolysaccharides (LPS). Murine caspase-11 binds cytosolic LPS, stimulates pyroptotic cell death, and drives sepsis pathogenesis. Extracellular priming factors enhance caspase-11-dependent pyroptosis. Herein we compare priming agents and demonstrate that IFNγ priming elicits the most rapid and amplified macrophage response to cytosolic LPS. Previous studies indicate that IFN-induced expression of caspase-11 and guanylate binding proteins (GBPs) are causal events explaining the effects of priming on cytosolic LPS sensing. We demonstrate that these events cannot fully account for the increased response triggered by IFNγ treatment. Indeed, IFNγ priming …

Best Practices For Successfully Writing And Publishing A Genome Announcement In Microbiology Resource Announcements, Julie C. Dunning Hotopp, David A. Baltrus, Vincent M. Bruno, John J. Dennehy, Steven R. Gill, Julia A. Maresca, Jelle Matthijnssens, Irene L. J. Newton, Catherine Putonti, David A. Rasko, Antonis Rokas, Simon Roux, Jason E. Stajich, Kenneth M. Stedman, Frank J. Stewart, J. Cameron Thrash

Biology Faculty Publications and Presentations

Microbiology Resource Announcements (MRA) provides peer-reviewed announcements of scientific resources for the microbial research community. We describe the best practices for writing an announcement that ensures that these publications are truly useful resources. Adhering to these best practices can lead to successful publication without the need for extensive revisions.

From Theory To Practice: Gathering Evidence For The Validity Of Data Collected With The Interdisciplinary Science Rubric (Idsr)., Brie Tripp, Erin E. Shortlidge

Biology Faculty Publications and Presentations

In a world of burgeoning societal issues, future scientists must be equipped to work inter-disciplinarily to address real-world problems. To train undergraduate students toward this end, practitioners must also have quality assessment tools to measure students' ability to think within an interdisciplinary system. There is, however, a dearth of instruments that accurately measure this competency. Using a theoretically and empirically based model, we developed an instrument, the Interdisciplinary Science Rubric (IDSR), to measure undergraduate students' interdisciplinary science thinking. An essay assignment was administered to 102 students across five courses at three different institutions. Students' work was scored with the newly …

No Water, No Problem: Stage-Specific Metabolic Responses To Dehydration Stress In Annual Killifish Embryos, Daniel E. Zajic, Jonathon P. Nicholson, Jason Podrabsky

Biology Faculty Publications and Presentations

Annual killifish survive in temporary ponds by producing drought-tolerant embryos that can enter metabolic dormancy (diapause). Survival of dehydration stress is achieved through severe reduction of evaporative water loss. We assessed dehydration stress tolerance in diapausing and developing embryos. We measured oxygen consumption rates under aquatic and aerial conditions to test the hypothesis that there is a trade-off between water retention and oxygen permeability. Diapausing embryos survive dehydrating conditions for over 1.5 years, and post-diapause stages can survive over 100 days. Diapausing embryos respond to dehydration stress by increasing oxygen consumption rates while post-diapause embryos exhibit the same or reduced …

Metabolomics Analysis Of Annual Killifish (Austrofundulus Limnaeus) Embryos During Aerial Dehydration Stress, Daniel Zajic, Jason Podrabsky

Biology Faculty Publications and Presentations

The annual killifish, Austrofundulus limnaeus, survives in ephemeral ponds in the coastal deserts of Venezuela. Persistence through the dry season is dependent on drought-resistant eggs embedded in the pond sediments during the rainy season. The ability of these embryos to enter drastic metabolic dormancy (diapause) during normal development enables A. limnaeus to survive conditions lethal to most other aquatic vertebrates; critical to the survival of the species is the ability of embryos to survive months and perhaps years without access to liquid water. Little is known about the molecular mechanisms that aid in survival of the dry season. This study …

Urban Air Quality Modeling: Evaluating Impacts Of Ecoroofs On Urban Air Quality In Portland, Oregon, Danlyn L. Brennan, Selina Teng

altREU Projects

In this work, the authors present a mathematical model simulating the impact of ecoroof vegetation on air quality in an urban microclimate. An ecoroof is a layer of vegetation established on rooftops to reduce stormwater runoff, mitigate heat, and enhance air quality. Certain plant species in ecoroofs may however have a detrimental effect on air quality, due to their emission of biogenic volatile organic compounds (BVOCs), which include potentially reactive species such as isoprene. These chemical species can interact with urban air pollution, particularly NOx produced by car traffic, to create other harmful pollutants such as ozone and particulate matter …

Connexin-46/50 In A Dynamic Lipid Environment Resolved By Cryoem At 1.9 Å, Jonathan A. Flores, Bassam G. Haddad, Kimberly A. Dolan, Janette Bernadette Myers, Craig C. Yoshioka, Jeremy Yoshioka, Daniel M. Zuckerman, Steve L. Reichow

Chemistry Faculty Publications and Presentations

Gap junctions establish direct pathways for cells to transfer metabolic and electrical messages. The local lipid environment is known to affect the structure, stability and intercellular channel activity of gap junctions; however, the molecular basis for these effects remains unknown. Here, we incorporate native connexin-46/50 (Cx46/50) intercellular channels into a dual lipid nanodisc system, mimicking a native cell-to-cell junction. Structural characterization by CryoEM reveals a lipid-induced stabilization to the channel, resulting in a 3D reconstruction at 1.9 Å resolution. Together with all-atom molecular dynamics simulations, it is shown that Cx46/50 in turn imparts long-range stabilization to the dynamic local lipid …

Hypergraph Analysis Of Structure Models, Cliff A. Joslyn, Teresa D. Schmidt, Martin Zwick

Systems Science Faculty Publications and Presentations

Theoretical discussion on the analysis of hypergraph networks; application of analysis methods to hypergraph networks derived by applying Reconstructability Analysis to health care data (the PhD dissertation work of Teresa Schmidt).

Host-Dependent Differences In Replication Strategy Of The Sulfolobus Spindle-Shaped Virus Strain Ssv9 (A.K.A., Ssvk1): Infection Profiles In Hosts Of The Family Sulfolobaceae, Ruben M. Ceballos, Coyne Gareth Drummond, Carson Len Stacy, Elizabeth Padillo-Crespo, Kenneth M. Stedman

Biology Faculty Publications and Presentations

The Sulfolobus Spindle-shaped Virus (SSV) system has become a model for studying thermophilic virus biology, including archaeal host-virus interactions and biogeography. Several factors make the SSV system amenable to studying archaeal genetic mechanisms (e.g., CRISPRs) as well as virus-host interactions in high temperature acidic environments. Previously, we reported that SSVs exhibited differential infectivity on allopatric vs. sympatric hosts. We also noticed a wide host range for virus strain SSV9 (a.k.a., SSVK1). For decades, SSVs have been described as “non-lytic” double-stranded DNA viruses that infect species of the genus Sulfolobus and release virions via budding rather than host lysis. In this …

Undergraduate Biology Education Research Gordon Research Conference: A Meeting Report, Erin L. Dolan, Michelle Borrero, Kristine Callis-Duehl, Miranda M. Chen Musgrove, Joelyn De Lima, Isi Ero-Tolliver, Laci M. Gerhart, Emma Goodwin, Lindsey R. Hamilton, Meredith A. Henry, Jose Herrera, Bethany Huot, Stacey Kiser, Melissa E. Ko, Marcy E. Kravec, Mark Lee, Lisa B. Limeri, Melanie E. Peffer, Debra Pires, Juan S. Ramirez Lugo, Starlette M. Sharp, Nicole A. Suarez

Biology Faculty Publications and Presentations

The 2019 Undergraduate Biology Education Research Gordon Research Conference (UBER GRC), titled “Achieving Widespread Improvement in Undergraduate Education,” brought together a diverse group of researchers and practitioners working to identify, promote, and understand widespread adoption of evidence-based teaching, learning, and success strategies in undergraduate biology. Graduate students and postdocs had the additional opportunity to present and discuss research during a Gordon Research Seminar (GRS) that preceded the GRC. This report provides a broad overview of the UBER GRC and GRS and highlights major themes that cut across invited talks, poster presentations, and informal discussions. Such themes include the importance of …

Pre-Emptive Detection Of Mature Pine Drought Stress Using Multispectral Aerial Imagery, Nancy Grulke, Jason Maxfield, Phillip Riggan, Charlie Schrader-Patton

Biology Faculty Publications and Presentations

Drought, ozone (O₃), and nitrogen deposition (N) alter foliar pigments and tree crown structure that may be remotely detectable. Remote sensing tools are needed that pre-emptively identify trees susceptible to environmental stresses could inform forest managers in advance of tree mortality risk. Jeffrey pine, a component of the economically important and widespread western yellow pine in North America was investigated in the southern Sierra Nevada. Transpiration of mature trees differed by 20% between microsites with adequate (mesic (M)) vs. limited (xeric (X)) water availability as described in a previous study. In this study, in-the-crown morphological traits (needle chlorosis, …

Vulnerability Of Small Forest Patches To Fire In The Paraiba Do Sul River Valley, Southeast Brazil: Implications For Restoration Of The Atlantic Forest Biome, Betina J. Guedes, Klecia G. Massi, Cody Evers, Max Nielsen-Pincus

Environmental Science and Management Faculty Publications and Presentations

The Atlantic Forest biome, a biodiversity hotspot historically threatened by deforestation and human disturbance, has recently seen a net gain in native forest cover due to changes in land use, enactment of new laws, and substantial investment in restoration. Like many South American and global ecosystems, the Atlantic Forest biome has also experienced an increase in area burned by wildfire largely due to human ignitions, which threatens these gains. Our objective was to understand the vulnerability of protected areas and small patches of neotropical forest to fire in the Paraíba do Sul River Valley, Brazil, a region within the Atlantic …

Quantitative And Qualitative Approaches To Assess Tree Vigor And Stand Health In Dry Pine Forests, Nancy Grulke, Craig Bienz, Kate Hrinkevich, Jason Maxfield, Kellie Uyeda

Biology Faculty Publications and Presentations

Despite a critical need to evaluate effectiveness of forest treatments in improving stand health, practitioners lack quantitative, repeatable metrics to assess tree vigor and stand health. We evaluated canopy and whole tree attributes of ponderosa pine (Pinus ponderosa Dougl. Ex Laws) related to carbon balance, water balance, and susceptibility to insects and pathogens in dry, pine-dominated forest stands during a multi-year drought, an environmental challenge to stand resilience. Metrics of trees in two unmanaged, and seven treated forested stands, in both uplands and lowlands to develop the quantitative approach. Whole tree and crown attributes including needle length and color, branchlet …

Effects Of Management For Productivity On Adult Survival Of Snowy Plovers, Eleanor P. Gaines, Stephen J. Dinsmore, Michael T. Murphy

Biology Faculty Publications and Presentations

Understanding the factors contributing to variation in demographic parameters and their influences on population growth is fundamental to effective conservation of small populations, but this information is often not available. Among shorebirds, population growth is generally most sensitive to changes in adult survival so understanding the factors affecting this vital rate is important. We used a long‐term mark–resight dataset and Program MARK to examine the effect of management actions, initiated to improve nesting productivity, on adult survival in a threatened population of Snowy Plovers (Charadrius nivosus ) in Oregon, USA. Apparent adult survival averaged 0.71 ± 0.01 (SE), but …

Do Foliar Endophytes Matter In Litter Decomposition?, Emily R. Wolfe, Daniel J. Ballhorn

Biology Faculty Publications and Presentations

Litter decomposition rates are affected by a variety of abiotic and biotic factors, including the presence of fungal endophytes in host plant tissues. This review broadly analyzes the findings of 67 studies on the roles of foliar endophytes in litter decomposition, and their effects on decomposition rates. From 29 studies and 1 review, we compiled a comprehensive table of 710 leaf-associated fungal taxa, including the type of tissue these taxa were associated with and isolated from, whether they were reported as endo- or epiphytic, and whether they had reported saprophytic abilities. Aquatic (i.e., in-stream) decomposition studies of endophyte-affected litter were …

Genotypic Diversity And Host-Specificity Of Frankia Bacteria Associated With Sympatric Populations Of Alnus Rubra And Alnus Rhombifolia In Oregon, Mehmet Ali Balkan, Nathan U. Stewart, Emily S. Kauffman, Emily R. Wolfe, Daniel J. Ballhorn

Biology Faculty Publications and Presentations

Biological nitrogen fixation is one of the most critical processes contributing to ecosystem productivity and stability on a global scale. In temperate climates of the northern hemisphere, plant-root associated bacteria of the genus Frankia are the major nitrogen fixers in forest environments. Trees belonging to the genus Alnus are the most widespread hosts of Frankia in the Pacific Northwest, and a myriad of biotic and abiotic factors can influence the robustness of this symbiosis. Host identity and bacterial strain are important features that can impact Alnus-Frankia association, but little is known about the interplay of intrageneric hosts that co-occur in …

A Basic Ddradseq Two‐Enzyme Protocol Performs Well With Herbarium And Silica‐Dried Tissues Across Four Genera, Ingrid E. Jordon‐Thaden, James B. Beck, Catherine A. Rushworth, Michael D. Windham, Nick Diaz, Jason T. Cantley, Christopher T. Martine, Carl J. Rothfels

Biology Faculty Publications and Presentations

PREMISE: The ability to sequence genome-scale data from herbarium specimens would allow for the economical development of data sets with broad taxonomic and geographic sampling that would otherwise not be possible. Here, we evaluate the utility of a basic double-digest restriction site–associated DNA sequencing (ddRADseq) protocol using DNAs from four genera extracted from both silica-dried and herbarium tissue.

METHODS: DNAs from Draba, Boechera, Solidago, and Ilex were processed with a ddRADseq protocol. The effects of DNA degradation, taxon, and specimen age were assessed. RESULTS: Although taxon, preservation method, and specimen age affected data recovery, large phylogenetically informative data sets were …

Crossing Boundaries: Steps Toward Measuring Undergraduates' Interdisciplinary Science Understanding, Brie Tripp, Sophia A. Voronoff, Erin Shortlidge

Biology Faculty Publications and Presentations

A desired outcome of education reform efforts is for undergraduates to effectively integrate knowledge across disciplines in order to evaluate and address real-world issues. Yet there are few assessments designed to measure if and how students think interdisciplinarily. Here, a sample of science faculty were surveyed to understand how they currently assess students’ interdisciplinary science understanding. Results indicate that individual writing-intensive activities are the most frequently used assessment type (69%). To understand how writing assignments can accurately assess students’ ability to think interdisciplinarily, we used a preexisting rubric, designed to measure social science students’ interdisciplinary understanding, to assess writing assignments …

The Role Of Warm, Dry Summers And Variation In Snowpack On Phytoplankton Dynamics In Mountain Lakes, Isabella A. Olesky, Whitney S. Beck, Roderick W. Lammers, Cara E. Steger, Codie Wilson, Kyle R. Christianson, Kim Vincent, Gunnar Forrest Johnson, Pieter T.J. Johnson, Jill S. Baron

Geology Faculty Publications and Presentations

Climate change is altering biogeochemical, metabolic, and ecological functions in lakes across the globe. Historically, mountain lakes in temperate regions have been unproductive because of brief ice-free seasons, a snowmelt-driven hydrograph, cold temperatures, and steep topography with low vegetation and soil cover. We tested the relative importance of winter and summer weather, watershed characteristics, and water chemistry as drivers of phytoplankton dynamics. Using boosted regression tree models for 28 mountain lakes in Colorado, we examined regional, intraseasonal, and interannual drivers of variability in chlorophyll a as a proxy for lake phytoplankton. Phytoplankton biomass was inversely related to the maximum snow …

Unveiling Crucivirus Diversity By Mining Metagenomic Data, Ignacio De La Higuera, George Kasun, Ellis L. Torrance, Alyssa A. Pratt, Amberlee Maluenda, Jonathan Colombet, Maxime Bisseux, Viviane Ravet, Anisha Dayaram, Daisy Stainton, Simona Kraberger, Peyman Zawar-Reza, Sharyn Goldstien, James V. Briskie, Robyn White, Helen Taylor, Christopher Gomez, David G. Ainley, Jon S. Harding, Rafaela S. Fontenele, Joshua Schreck, Simone Ribeiro, Stephen A. Oswald, Jennifer M. Arnold, François Enault, Arvind Varsani, Kenneth M. Stedman

Biology Faculty Publications and Presentations

The discovery of cruciviruses revealed the most explicit example of a common protein homologue between DNA and RNA viruses to date. Cruciviruses are a novel group of circular Rep-encoding single-stranded DNA (ssDNA) (CRESSDNA) viruses that encode capsid proteins that are most closely related to those encoded by RNA viruses in the family Tombusviridae. The apparent chimeric nature of the two core proteins encoded by crucivirus genomes suggests horizontal gene transfer of capsid genes between DNA and RNA viruses. Here, we identified and characterized 451 new crucivirus genomes and 10 capsid-encoding circular genetic elements through de novo assembly and mining of …

Archaeosine Modification Of Archaeal Trna - A Role In Structural Stabilization, Ben Turner, Brett W. Burkhart, Katrin Weidenbach, Robert Ross, Patrick A. Limbach, Ruth A. Schmitz, Valérie De Crécy-Lagard, Kenneth M. Stedman, Thomas J. Santangelo, Dirk Iwata-Reuyl

Biology Faculty Publications and Presentations

Archaeosine (G+) is a structurally complex modified nucleoside found quasi-universally in the tRNA of Archaea and located at position 15 in the dihydrouridine loop, a site not modified in any tRNA outside of the Archaea. G+ is characterized by an unusual 7-deazaguanosine core structure with a formamidine group at the 7-position. The location of G+ at position 15, coupled with its novel molecular structure, led to a hypothesis that G+ stabilizes tRNA tertiary structure through several distinct mechanisms. To test whether G+ contributes to tRNA stability and define the biological role of G+, we investigated the consequences of introducing targeted …