Scholarly Works, Biological Sciences

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Hydrologic and geochemical drivers of aluminum, barium, and copper in two drinking water reservoirs in Southwestern Virginia, USA
Bauer, Carly E.; Wood, Cecelia E.; Lofton, Mary E.; Breef-Pilz, Adrienne; Carey, Cayelan C.; Schreiber, Madeline E. (IWA Publishing, 2025-11-24)
The water quality of drinking water reservoirs is critical for human and ecosystem health. In this study, we examined the drivers of three metals, aluminum (Al), barium (Ba), and copper (Cu), across two drinking water reservoirs in southwestern Virginia, USA, over 4 years. One reservoir has a hypolimnetic oxygenation system; the other does not. We used time series modeling and multivariate analysis of water column chemistry, suspended sediment, inflow, and precipitation data to assess the relative roles of hydrologic and geochemical drivers of metal behaviors in the two reservoirs. Results suggest that Al concentrations were primarily influenced by high-flow events, consistent with the mobilization of clays from physical weathering. In contrast, Ba showed stronger sensitivity to geochemical drivers, specifically redox conditions. Drivers of Cu behavior were obscured by low Cu concentrations. For all metals, patterns varied among years. Our findings highlight the importance of long-term monitoring and integrated approaches to evaluate the drivers of metal dynamics in reservoir ecosystems and inform strategies for maintaining safe drinking water supplies.
Parasite escape mechanisms drive morphological diversification in avian lice
Kolencik, Stanislav; Stanley, Edward L.; Punnath, Aswaj; Grant, Avery R.; Dona, Jorge; Johnson, Kevin P.; Allen, Julie M. (Royal Society, 2024-03-27)
Organisms that have repeatedly evolved similar morphologies owing to the same selective pressures provide excellent cases in which to examine specific morphological changes and their relevance to the ecology and evolution of taxa. Hosts of permanent parasites act as an independent evolutionary experiment, as parasites on these hosts are thought to be undergoing similar selective pressures. Parasitic feather lice have repeatedly diversified into convergent ecomorphs in different microhabitats on their avian hosts. We quantified specific morphological characters to determine (i) which traits are associated with each ecomorph, (ii) the quantitative differences between these ecomorphs, and (iii) if there is evidence of displacement among co-occurring lice as might be expected under louse-louse competition on the host. We used nano-computed tomography scan data of 89 specimens, belonging to four repeatedly evolved ecomorphs, to examine their mandibular muscle volume, limb length and three-dimensional head shape data. Here, we find evidence that lice repeatedly evolve similar morphologies as a mechanism to escape host defences, but also diverge into different ecomorphs related to the way they escape these defences. Lice that co-occur with other genera on a host exhibit greater morphological divergence, indicating a potential role of competition in evolutionary divergence.
Neurogenomic landscape associated with status-dependent cooperative behaviour
Bolton, Peri; Ryder, T. Brandt; Dakin, Roslyn; Houtz, Jennifer; Moore, Ignacio T.; Balakrishnan, Christopher; Horton, Brent (Wiley, 2025-08-01)
The neurogenomic mechanisms mediating male-male reproductive cooperative behaviours remain unknown. We leveraged extensive transcriptomic and behavioural data on a neotropical bird species (Pipra filicauda) that performs cooperative courtship displays to understand these mechanisms. In this species, the cooperative display is modulated by testosterone, which promotes cooperation in non-territorial birds, but suppresses cooperation in territory holders. We sought to understand the neurogenomic underpinnings of three related traits: social status, cooperative display behaviour and testosterone phenotype. To do this, we profiled gene expression in 10 brain nuclei spanning the social decision-making network (SDMN), and two key endocrine tissues that regulate social behaviour. We associated gene expression with each bird's behavioural and endocrine profile derived from 3 years of repeated measures taken from free-living birds in the Ecuadorian Amazon. We found distinct landscapes of constitutive gene expression were associated with social status, testosterone phenotype and cooperation, reflecting the modular organization and engagement of neuroendocrine tissues. Sex-steroid and neuropeptide signalling appeared to be important in mediating status-specific relationships between testosterone and cooperation, suggesting shared regulatory mechanisms with male aggressive and sexual behaviours. We also identified differentially regulated genes involved in cellular activity and synaptic potentiation, suggesting multiple mechanisms underpin these genomic states. Finally, we identified SDMN-wide gene expression differences between territorial and floater males that could form the basis of 'status-specific' neurophysiological phenotypes, potentially mediated by testosterone and growth hormone. Overall, our findings provide new, systems-level insights into the mechanisms of cooperative behaviour and suggest that differences in neurogenomic state are the basis for individual differences in social behaviour.
Propagation of monocyte exhaustion memory and underlying mechanisms
Wang, Jing; Caldwell, Blake A.; Wu, Yajun; Razani, Babak; Li, Liwu (2025-12-05)
Monocyte exhaustion is a dysfunctional state characterized by prolonged pathogenic inflammation and immune suppression, commonly observed in chronic infections and sepsis. However, the mechanisms underlying the generation and propagation of exhausted monocytes remain poorly understood. In this study, we investigate the impacts of exhausted monocytes on neighboring naïve monocytes, endothelial cells, and T cell function. Using an in vitro co-culture system, we demonstrate that exhausted monocytes induced by prolonged LPS stimulation propagate the exhaustion phenotype to neighboring naïve monocytes. Meanwhile these exhausted monocytes can promote endothelial apoptosis, upregulate adhesion molecules ICAM-1 and VCAM-1, and enhance monocyte transmigration, contributing to endothelial dysfunction. Pharmacological inhibition of CD38, a key marker of monocyte exhaustion, significantly mitigates these effects, highlighting its critical role in monocyte-driven endothelial alterations. Furthermore, we show that exhausted monocytes suppress T cell proliferation and activation, a process reversed by CD38 inhibition. We also identify mTOR signaling as a key regulator of monocyte exhaustion and its propagation, with mTOR inhibition partially restoring monocyte functionality by downregulating exhaustion markers and STAT1/STAT3/S6K signaling. Collectively, our findings highlight the CD38-mTOR axis as a central driver of monocyte exhaustion and its pathological consequences, offering potential therapeutic targets for reversing immune dysfunction in inflammatory diseases. Graphical Abstract The inhibition of CD38 can alleviate monocyte exhaustion through suppressing the sustained mTORC1-STAT1 activation. Upon LPS stimulation, TLR4 signaling is activated through the TRAM-TRIF adaptor complex, leading to the phosphorylation of Src. This activation promotes mTORC1 signaling, characterized by the recruitment of Raptor and the activation of S6K. mTORC1 activation subsequently drives STAT1/3 signaling, which further induces CD38 expression and forms a sustained positive feedback loop. Elevated CD38 levels contribute to monocyte exhaustion by depleting NAD⁺, a key metabolic cofactor. NAD⁺ depletion negatively impacts mTORC2 signaling, leading to impaired Akt phosphorylation, resulting in diminished expression of PGC1α/β, CREB and CD86, both of which are associated with exhausted monocyte immune suppression. The CD38 inhibitor 78c disrupts this exhaustion pathway, offering a potential therapeutic strategy to mitigate monocyte dysfunction during monocyte exhaustion.
Subsidy-stress responses of ecosystem functions along experimental freshwater salinity gradients
DeVilbiss, Stephen E.; Badgley, Brian D.; Hotchkiss, Erin R.; Steele, Meredith K. (Springer, 2024-05-01)
Human activity is increasing salt concentrations in freshwaters worldwide, but effects of freshwater salinity gradients on biogeochemical cycling are less understood than in saline, brackish, or marine environments. Using controlled microcosm experiments, we characterized (1) short-term (one to five days) biogeochemical responses and (2) water column metabolism along a freshwater salinity gradient of multiple salt types. After one day, microcosms were oxic (4.48-7.40 mg O2 L-1) but became hypoxic (1.20-3.31 mg L-1) by day five. After one day in oxic conditions, microbial respiration in magnesium-, sodium-, and sea salt-based salinity treatments showed a subsidy-stress response, with respiration increasing by over 100% as salinity increased from 30 to 350-800 mu S cm-1. Conversely, respiration consistently increased along a calcium-based salinity gradient, peaking at 1500 mu S cm-1. By day five, an inverse subsidy-stress response was observed with elevated respiration at upper or lower ends of the gradient except for the magnesium treatment, which had the lowest respiration at the highest salinity. Calcium- and magnesium-based salinity treatments also caused considerable changes in phosphorus concentrations and C:P and N:P. In a separate experiment, microbial respiration and water column primary production also displayed subsidy-stress responses, but imbalances in effect sizes caused consistently declining net community production with increasing salinity. Collectively, our results establish that short-term exposure to different salt ion concentrations can enhance freshwater biogeochemical cycling at relatively low concentrations and alter resource stoichiometry. Furthermore, the nature of effects of freshwater salinization may also change with oxygen availability.
McMurdo Dry Valley lake edge 'moats': the ecological intersection between terrestrial and aquatic polar desert habitats
Stone, Michael S.; Devlin, Shawn P.; Hawes, Ian; Welch, Kathleen A.; Gooseff, Michael N.; Takacs-Vesbach, Cristina; Morgan-Kiss, Rachael; Adams, Byron J.; Barrett, John E.; Priscu, John C.; Doran, Peter T. (Cambridge University Press, 2024-04-19)
Aquatic ecosystems - lakes, ponds and streams - are hotspots of biodiversity in the cold and arid environment of Continental Antarctica. Environmental change is expected to increasingly alter Antarctic aquatic ecosystems and modify the physical characteristics and interactions within the habitats that they support. Here, we describe physical and biological features of the peripheral 'moat' of a closed-basin Antarctic lake. These moats mediate connectivity amongst streams, lake and soils. We highlight the cyclical moat transition from a frozen winter state to an active open-water summer system, through refreeze as winter returns. Summer melting begins at the lakebed, initially creating an ice-constrained lens of liquid water in November, which swiftly progresses upwards, creating open water in December. Conversely, freezing progresses slowly from the water surface downwards, with water at 1 m bottom depth remaining liquid until May. Moats support productive, diverse benthic communities that are taxonomically distinct from those under the adjacent permanent lake ice. We show how ion ratios suggest that summer exchange occurs amongst moats, streams, soils and sub-ice lake water, perhaps facilitated by within-moat density-driven convection. Moats occupy a small but dynamic area of lake habitat, are disproportionately affected by recent lake-level rises and may thus be particularly vulnerable to hydrological change.
Interacting impacts of hydrological changes and air temperature warming on lake temperatures highlight the potential for adaptive management
Olsson, Freya; Mackay, Eleanor B.; Spears, Bryan M.; Barker, Philip; Jones, Ian D. (Springer, 2025-03-01)
Globally, climate warming is increasing air temperatures and changing river flows, but few studies have explicitly considered the consequences for lake temperatures of these dual effects, or the potential to manage lake inflows to mitigate climate warming impacts. Using a one-dimensional model, we tested the sensitivity of lake temperatures to the separate and interacting effects of changes in air temperature and inflow on a small, short-residence time (annual average approximate to 20 days), temperate lake. Reducing inflow by 70% increased summer lake surface temperatures 1.0-1.2 degrees C and water column stability by 11-19%, equivalent to the effect of 1.2 degrees C air temperature warming. Conversely, similar increases in inflow could result in lake summer cooling, sufficient to mitigate 0.75 degrees C air temperature rise, increasing to more than 1.1 degrees C if inflow temperature does not rise. We discuss how altering lake inflow volume and temperature could be added to the suite of adaptation measures for lakes.
Untargeted Metabolomics Reveals Fruit Secondary Metabolites Alter Bat Nutrient Absorption
Gelambi, Mariana; Whitehead, Susan R. (Springer, 2024-08-01)
The ecological interaction between fleshy fruits and frugivores is influenced by diverse mixtures of secondary metabolites that naturally occur in the fruit pulp. Although some fruit secondary metabolites have a primary role in defending the pulp against antagonistic frugivores, these metabolites also potentially affect mutualistic interactions. The physiological impact of these secondary metabolites on mutualistic frugivores remains largely unexplored. Using a mutualistic fruit bat (Carollia perspicillata), we showed that ingesting four secondary metabolites commonly found in plant tissues affects bat foraging behavior and induces changes in the fecal metabolome. Our behavioral trials showed that the metabolites tested typically deter bats. Our metabolomic surveys suggest that secondary metabolites alter, either by increasing or decreasing, the absorption of essential macronutrients. These behavioral and physiological effects vary based on the specific identity and concentration of the metabolite tested. Our results also suggest that a portion of the secondary metabolites consumed is excreted by the bat intact or slightly modified. By identifying key shifts in the fecal metabolome of a mutualistic frugivore caused by secondary metabolite consumption, this study improves our understanding of the effects of fruit chemistry on frugivore physiology.
Injury-induced connexin 43 expression regulates endothelial wound healing
Sedovy, Meghan W.; Renton, Mark C.; Roberts, Kailynn; Leng, Xinyan; Dennison, Clare L.; Toler, Caroline O.; Leaf, Melissa R.; Lampe, Paul D.; Best, Angela K.; Isakson, Brant E.; Johnstone, Scott R. (American Physiological Society, 2025-10-28)
Endothelial cell (EC) injury is a major contributing factor to vascular surgical failure. As such, understanding the mechanisms of endothelial healing is essential to the development of vascular therapeutics and procedures. Gap junctions formed by connexin 43 (Cx43) are implicated in regulating skin wound healing, but their role in endothelial healing is unknown. Secondary analysis of RNA-seq data from in vivo injured mouse aortas (GEO: GSE115618) identified significant Cx43 upregulation in EC postinjury. We developed a novel in vivo model of EC injury using mouse carotid artery ligation to test the role of Cx43. We identified that EC immediately adjacent to the wound edge upregulate Cx43 protein expression, predominantly at cell-cell junctions. We show significantly delayed EC healing in a mouse model of inducible EC-specific Cx43 deletion [EC-Cx43 knockout (KO)] at 24 h post ligation. Single-cell RNA-seq analysis of 10,829 cells from 18 h injured EC-wild type (WT) and EC-Cx43 KO carotids revealed a Cx43-associated reduction in enrichment of EC pathways associated with migration, proliferation, and ERK/MAPK signaling pathways. Finally, the importance of Cx43 phosphorylation on EC healing was tested in mice with single-point alanine mutations (phospho-null) in known phosphorylation sites that alter Cx43 channel assembly and opening. Mice containing alanine mutations at ERK phosphorylated Cx43 serines (Cx43S²⁵⁵/²⁶²/²⁷⁹/²⁸²A) have reduced healing rates similar to EC-Cx43 KO mice. These data suggest that EC injury-induced Cx43 upregulation and subsequent Cx43 gap junction-mediated cell-to-cell communication are required for normal EC migration during wound healing after vascular injury.
Drivers of population dynamics of at-risk populations change with pathogen arrival
Grimaudo, Alexander T.; Hoyt, Joseph R.; King, R. Andrew; Toomey, Rickard S.; Simpson, Chris; Holliday, Cory; Silvis, Alexander; Doyle, Rick T.; Kath, Joseph A.; Armstrong, Mike P.; Brack Jr, Virgil; Reynolds, Richard J.; Williamson, Ryan H.; Turner, Gregory G.; Kuczynska, Vona; Meyer, Jordan J.; Jansky, Kyle; Herzog, Carl J.; Hopkins, Skylar R.; Langwig, Kate E. (Elsevier, 2024-08-01)
Successful wildlife conservation in an era of global change requires understanding determinants of species population growth. However, when populations are faced with novel stressors, factors associated with healthy populations can change, necessitating shifting conservation strategies. For example, emerging infectious diseases can cause conditions previously beneficial to host populations to increase disease impacts. Here, we paired a population dataset of 265 colonies of the federally endangered Indiana bat (Myotis sodalis) with 50.7 logger-years of environmental data to explore factors that affected colony response to white-nose syndrome (WNS), an emerging fungal disease. We found variation in colony responses to WNS, ranging from extirpation to stabilization. The severity of WNS impacts was associated with hibernaculum temperature, as colonies of cold hibernacula declined more severely than those in relatively warm hibernacula, an association that arose following pathogen emergence. Interestingly, this association was opposite that of a sympatric bat species, the little brown bat (Myotis lucifugus), illustrating that environmental dependence of disease can vary by species in a multi-host community. Simulating future colony dynamics suggests that most extirpations have already occurred, as the pathogen has been present for several years in most colonies, and that relatively small colonies are more susceptible to extirpation. Overall, this study illustrates that emerging infectious diseases can change the factors associated with host population growth, including through novel environmental associations that vary by host species. Consideration of these shifting associations and differences between impacted species will be essential to the conservation of host communities challenged by emerging infectious disease.
Variability in Ice Cover Does Not Affect Annual Metabolism Estimates in a Small Eutrophic Reservoir
Howard, Dexter W.; Brentrup, Jennifer A.; Richardson, David C.; Lewis, Abigail S. L.; Olsson, Freya; Carey, Cayelan C. (American Geophysical Union, 2024-07-01)
Temperate reservoirs and lakes worldwide are experiencing decreases in ice cover, which will likely alter the net balance of gross primary production (GPP) and respiration (R) in these ecosystems. However, most metabolism studies to date have focused on summer dynamics, thereby excluding winter dynamics from annual metabolism budgets. To address this gap, we analyzed 6 years of year-round high-frequency dissolved oxygen data to estimate daily rates of net ecosystem production (NEP), GPP, and R in a eutrophic, dimictic reservoir that has intermittent ice cover. Over 6 years, the reservoir exhibited slight heterotrophy during both summer and winter. We found winter and summer metabolism rates to be similar: summer NEP had a median rate of -0.06 mg O2 L-1 day-1 (range: -15.86 to 3.20 mg O2 L-1 day-1), while median winter NEP was -0.02 mg O2 L-1 day-1 (range: -8.19 to 0.53 mg O2 L-1 day-1). Despite large differences in the duration of ice cover among years, there were minimal differences in NEP among winters. Overall, the inclusion of winter data had a limited effect on annual metabolism estimates in a eutrophic reservoir, likely due to short winter periods in this reservoir (ice durations 0-35 days), relative to higher-latitude lakes. Our work reveals a smaller difference between winter and summer NEP than in lakes with continuous ice cover. Ultimately, our work underscores the importance of studying full-year metabolism dynamics in a range of aquatic ecosystems to help anticipate the effects of declining ice cover across lakes worldwide. Lakes and reservoirs around the world are experiencing decreases in ice cover duration, with many waterbodies starting to experience non-continuous ice cover throughout the winter. These changes in ice duration have the potential to influence carbon cycling, but to date few long-term studies have included winter data. We analyzed 6 years of minute-resolution oxygen data from a small reservoir that experiences non-continuous ice cover to estimate whether the surface water was a source or sink of carbon at daily, seasonal, and annual scales. We found that the reservoir was often a source of carbon to the atmosphere, regardless of whether data from winter were included. Our results differed from previous studies conducted in higher-latitude lakes that experience continuous ice cover throughout the winter, potentially due to the already-short duration of ice cover in this reservoir. As the duration of ice cover continues to decrease across lakes and reservoirs worldwide, our work highlights the need for studying how changing winter conditions-especially non-continuous ice cover-affects year-round carbon cycling. Winter data have rarely been included in lake metabolism studies, limiting our understanding of how ice affects metabolism estimates Annual metabolism estimates were similar across 6 years with widely varying ice cover Water chemistry explained variability in daily gross primary production, but not respiration or net ecosystem production, over 6 years
Microplastic burden in native (Cambarus appalachiensis) and non-native (Faxonius cristavarius) crayfish along semi-rural and urban streams in southwest Virginia, USA
Gray, Austin D.; Mayer, Kathleen; Gore, Beija; Gaesser, Megan; Ferguson, Nathan (Academic Press – Elsevier, 2024-10-01)
Our comparative assessment is the first study to investigate microplastic body burden in native (Cambarus appalachiensis) and non-native (Faxonius cristavarius) crayfish along a semi-rural and urban stream across different seasons. Crayfish, sediment, and surface water were collected, processed, and characterized using mu Raman spectroscopy to compare microplastic polymer types and shapes across compartments. Average surface water concentrations were significantly higher in our urban stream compared to our semi-rural stream (17.3 +/- 2.4 particles/L and 9.9 +/- 1.3 particles/L, respectively; P = 0.015). Average sediment concentrations were similar between urban and semi-rural streams (140 +/- 14.5 particles/kg and 139 +/- 22.5 particles/kg, respectively; P = 0.957). Our findings showed a significant interactive effect of season, site, and nativity (i.e., species) regarding microplastic body burden in crayfish (P = 0.004). The smaller, non-native crayfish amassed more microplastic particles than the native crayfish (0.4-2.0 particles/g versus 0.4-0.8 particles/g, respectively). Fibers and fragments were the most common polymer shapes across compartments, with white and black being the dominant particle colors. Our study identified 13 plastic polymer types in crayfish and three in surface water and sediment; polypropylene was the most common polymer across compartments. This study provides evidence that crayfish body burden of microplastics can differ across species, seasons, and locations, highlighting the need for future studies to consider that sublethal impacts associated with microplastic body burden may vary by region and species.
Effects of climate change on seed germination may contribute to habitat homogenization in freshwater forested wetlands
Carr, Kori; Ozowara, Xavier; Sloey, Taylor M. (Springer, 2024-10-01)
Climate changes in temperate regions are expected to result in warmer, shorter winters in temperate latitudes. These changes may have consequences for germination of plant species that require a period of physiological dormancy. The effect of cold duration on seed germination has been investigated in a number of plant taxa, but has not been well studied in wetland and bottomland forest tree species, an ecosystem that is threatened by habitat homogenization. Our work sought to test the role of changing winter temperatures on seed germination in specialist (Nyssa aquatica and Taxodium distichum) and generalist (Acer rubrum and Liquidambar styraciflua) tree species within forested wetlands throughout the eastern U.S. The experiment was conducted in an environmental chamber in Norfolk, VA, USA. Seeds of T. distichum, N. aquatica, A. rubrum, and L. styraciflua were exposed to each of seven pre-germination cold exposure durations (0, 15, 30, 45, 60, 75, and 90 days) and observed for germination for 30 days. Cold stratification duration positively impacted total percent germination in N. aquatica (p < 0.0001) as well as A. rubrum (p = 0.0008) and T. distichum (p = 0.05). Liquidambar styraciflua seeds exhibited more rapid rates of germination with increasing cold exposure duration and greater percent germination compared to the others regardless of cold stratification duration. Our results provide insight into how community dynamics and biodiversity of wetland and bottomland trees may shift with a changing climate. Further, this work emphasizes the importance of understanding the role of plant functional traits in early life stages in community dynamics and has implications for management practices.
Individual-based modelling of adaptive physiological traits of cyanobacteria: Responses to light history
Ranjbar, Mohammad Hassan; Hamilton, David P.; Pace, Michael L.; Etemad-Shahidi, Amir; Carey, Cayelan C.; Helfer, Fernanda (Elsevier, 2024-09-01)
Adaptive physiological traits of cyanobacteria allow plasticity of responses to environmental change at multiple time scales. Most conventional phytoplankton models only simulate responses to current conditions without incorporating antecedent environmental history and adaptive physiological traits, thereby potentially missing mechanisms that influence dynamics. We developed an individual-based model (IBM) that incorporates information on light exposure history and cell physiology coupled with a hydrodynamic model that simulates mixing and transport. The combined model successfully simulated cyanobacterial growth and respiration in a whole-lake nutrient enrichment experiment in a temperate lake (Peter Lake, Michigan, USA). The model also incorporates non-photochemical quenching (NPQ) to improve simulations of cyanobacteria biomass based on validation against cyanobacteria cell counts and chlorophyll concentration. The IBM demonstrated that physical processes (stratification and mixing) significantly affect the dynamics of NPQ in cyanobacteria. Cyanobacteria had high fluorescence quenching and long photo-physiological relaxation periods during stratification, and low quenching and rapid relaxation in response to low light exposure history as the mixing layer deepened. This work demonstrates that coupling adaptive physiological trait with physical mixing into models can improve our understanding and enhance predictions of bloom occurrences in response to environmental changes.
Impacts of invasion on a freshwater cleaning symbiosis
Bell, Spencer S.; McElmurray, Philip; Creed, Robert P.; Brown, Bryan L. (Springer, 2024-08-01)
Organismal invasions have repeatedly been cited as a driving force behind the loss of biodiversity. Unlike many other impacts of invasion, the effect of invasion on native symbiont communities has received less attention. The introduction of invasive hosts presents a potential opportunity to native symbionts; invasive hosts could benefit native symbionts through providing a novel host environment that improves symbiont fitness relative to their fitness on native hosts. Alternatively, invasive hosts could noncompetent hosts for native symbionts, resulting in negative impacts on native symbiont abundance and diversity. Crayfish in the northern hemisphere host diverse assemblages of obligate annelid symbionts (P: Anellida, O: Branchiobdellida). Two invasive crayfish hosts in the genus Faxonius have been introduced and are interacting with the native crayfish hosts and their symbionts in three watersheds in western Virginia, USA. Previous studies suggest that the invasive host F. cristavarius is a less competent host for symbionts compared to native hosts in the genus Cambarus. We carried out an extensive survey in these watersheds to determine impacts of varying degrees of invasion on branchiobdellidan abundance and diversity. We also conducted a complementary host replacement experiment to investigate how increases in the relative abundance of invasive hosts contributes to observed patterns of symbiont abundance and diversity in the field. In our survey, as the proportion of invasive hosts at a site increased, branchiobdellidan abundance and diversity declined significantly. In the experiment, the worms dispersed onto both native and invasive hosts. As the percentage of noncompetent F. cristavarius hosts increased, the survival of branchiobdellidans declined. Both symbiont survival and opportunities for successful dispersal are reduced as this noncompetent invasive host progressively displaces native hosts, which imperils the integrity of native host-symbiont systems. Given that many native hosts accrue significant fitness benefits from their relationships with native symbionts, including hosts in our study system, losses of beneficial symbionts may produce a positive feedback loop that decreases invasion resistance of native species, exacerbates the effects of invasions, and presents a major conservation issue in invaded systems.
Membrane Composition Modulates Vp54 Binding: A Combined Experimental and Computational Study
Guo, Wenhan; Dong, Rui; Okedigba, Ayoyinka O.; Sanchez, Jason E.; Agarkova, Irina V.; Abisamra, Elea-Maria; Jelinsky, Andrew; Riekhof, Wayne; Noor, Laila; Dunigan, David D.; Van Etten, James L.; Capelluto, Daniel G. S.; Xiao, Chuan; Li, Lin (MDPI, 2025-10-03)
The recruitment of peripheral membrane proteins is tightly regulated by membrane lipid composition and local electrostatic microenvironments. Our experimental observations revealed that Vp54, a viral matrix protein, exhibited preferential binding to lipid bilayers enriched in anionic lipids such as phosphatidylglycerol (PG) and phosphatidylserine (PS), compared to neutral phosphatidylcholine/phosphatidylethanolamine liposomes, and this occurred in a curvature-dependent manner. To elucidate the molecular basis of this selective interaction, we performed a series of computational analyses including helical wheel projection, electrostatic potential calculations, electric field lines simulations, and electrostatic force analysis. Our results showed that the membrane-proximal region of Vp54 adopted an amphipathic α-helical structure with a positively charged interface. In membranes containing PG or PS, electrostatic potentials at the interface were significantly more negative, enhancing attraction with Vp54. Field line and force analyses further confirmed that both the presence and spatial clustering of anionic lipids intensify membrane–Vp54 electrostatic interactions. These computational findings align with experimental binding data, jointly demonstrating that membrane lipid composition and organization critically modulate Vp54 recruitment. Together, our findings highlight the importance of electrostatic complementarity and membrane heterogeneity in peripheral protein targeting and provide a framework applicable to broader classes of membrane-binding proteins.
Integrating Data Science Into Undergraduate Science and Engineering Courses: Lessons Learned by Instructors in a Multiuniversity Research-Practice Partnership
Naseri, Md. Yunus; Snyder, Caitlin; Perez-Rivera, Katherine X.; Bhandari, Sambridhi; Workneh, Habtamu Alemu; Aryal, Niroj; Biswas, Gautam; Henrick, Erin C.; Hotchkiss, Erin R.; Jha, Manoj K.; Jiang, Steven; Kern, Emily C.; Lohani, Vinod K.; Marston, Landon T.; Vanags, Christopher P.; Xia, Kang (IEEE, 2025-02-01)
Contribution: This article discusses a research-practice partnership (RPP) where instructors from six undergraduate courses in three universities developed data science modules tailored to the needs of their respective disciplines, academic levels, and pedagogies. Background: STEM disciplines at universities are incorporating data science topics to meet employer demands for data science-savvy graduates. Integrating these topics into regular course materials can benefit students and instructors. However, instructors encounter challenges in integrating data science instruction into their course schedules. Research Questions: How did instructors from multiple engineering and science disciplines working in an RPP integrate data science into their undergraduate courses? Methodology: A multiple case study approach, with each course as a unit of analysis, was used to identify data science topics and integration approaches. Findings: Instructors designed their modules to meet specific course needs, utilizing them as primary or supplementary learning tools based on their course structure and pedagogy. They selected a subset of discipline-agnostic data science topics, such as generating and interpreting visualizations and conducting basic statistical analyses. Although instructors faced challenges due to varying data science skills of their students, they valued the control they had in integrating data science content into their courses. They were uncertain about whether the modules could be adopted for use by other instructors, specifically by those outside of their discipline, but they all believed the approach for developing and integrating data science could be adapted to student needs in different situations.
Newton's cradle: Cell cycle regulation by two mutually inhibitory oscillators
Dragoi, Calin-Mihai; Tyson, John J.; Novak, Bela (Elsevier, 2024-11-01)
The cell division cycle is a fundamental physiological process displaying a great degree of plasticity during the course of multicellular development. This plasticity is evident in the transition from rapid and stringently-timed divisions of the early embryo to subsequent size-controlled mitotic cycles. Later in development, cells may pause and restart proliferation in response to myriads of internal or external signals, or permanently exit the cell cycle following terminal differentiation or senescence. Beyond this, cells can undergo modified cell division variants, such as endoreplication, which increases their ploidy, or meiosis, which reduces their ploidy. This wealth of behaviours has led to numerous conceptual analogies intended as frameworks for understanding the proliferative program. Here, we aim to unify these mechanisms under one dynamical paradigm. To this end, we take a control theoretical approach to frame the cell cycle as a pair of arrestable and mutually-inhibiting, doubly amplified, negative feedback oscillators controlling chromosome replication and segregation events, respectively. Under appropriate conditions, this framework can reproduce fixed-period oscillations, checkpoint arrests of variable duration, and endocycles. Subsequently, we use phase plane and bifurcation analysis to explain the dynamical basis of these properties. Then, using a physiologically realistic, biochemical model, we show that the very same regulatory structure underpins the diverse functions of the cell cycle control network. We conclude that Newton's cradle may be a suitable mechanical analogy of how the cell cycle is regulated.
Julian Hirniak, an early proponent of periodic chemical reactions
Manz, Niklas; Holovatch, Yurij; Tyson, John J. (Springer, 2024-10-01)
In this article we present and discuss the work and scientific legacy of Julian Hirniak, the Ukrainian chemist and physicist who published two articles in 1908 and 1911 about periodic chemical reactions. Over the last 110+ years, his theoretical work has often been cited favorably in connection with Alfred Lotka's theoretical model of an oscillating reaction system. Other authors have pointed out thermodynamic problems in Hirniak's reaction scheme. Based on English translations of his 1908 Ukrainian and 1911 German articles, we show that Hirniak's claim (that a cycle of inter-conversions of three chemical isomers in a closed reaction vessel can show damped periodic behavior) violates the Principle of Detailed Balance (i.e., the Second Law of Thermodynamics), and that Hirniak was aware of this Principle. We also discuss his results in relation to Lotka's first model of damped oscillations in an open system of chemical reactions involving an auto-catalytic reaction operating far from equilibrium. Taking hints from both Hirniak and Lotka, we show that the mundane case of a kinase enzyme catalyzing the phosphorylation of a sugar can satisfy Hirniak's conditions for damped oscillations to its steady state flux (i.e., the Michaelis-Menten rate law), but that the oscillations are so highly damped as to be unobservable. Finally, we examine historical and factual misunderstandings related to Julian Hirniak and his publications.
CO2 and CH4 Concentrations in Headwater Wetlands Influenced by Morphology and Changing Hydro-Biogeochemical Conditions
Lloreda, Carla Lopez; Maze, James; Wardinski, Katherine; Corline, Nicholas; Mclaughlin, Daniel; Jones, C. Nathan; Scott, Durelle; Palmer, Margaret; Hotchkiss, Erin R. (Springer, 2024-11-01)
Headwater wetlands are important sites for carbon storage and emissions. While local- and landscape-scale factors are known to influence wetland carbon biogeochemistry, the spatial and temporal heterogeneity of these factors limits our predictive understanding of wetland carbon dynamics. To address this issue, we examined relationships between carbon dioxide (CO2) and methane (CH4) concentrations with wetland hydrogeomorphology, water level, and biogeochemical conditions. We sampled water chemistry and dissolved gases (CO2 and CH4) and monitored continuous water level at 20 wetlands and co-located upland wells in the Delmarva Peninsula, Maryland, every 1-3 months for 2 years. We also obtained wetland hydrogeomorphologic metrics at maximum inundation (area, perimeter, and volume). Wetlands in our study were supersaturated with CO2 (mean = 315 mu M) and CH4 (mean = 15 mu M), highlighting their potential role as carbon sources to the atmosphere. Spatial and temporal variability in CO2 and CH4 concentrations was high, particularly for CH4, and both gases were more spatially variable than temporally. We found that groundwater is a potential source of CO2 in wetlands and CO2 decreases with increased water level. In contrast, CH4 concentrations appear to be related to substrate and nutrient availability and to drying patterns over a longer temporal scale. At the landscape scale, wetlands with higher perimeter:area ratios and wetlands with higher height above the nearest drainage had higher CO2 and CH4 concentrations. Understanding the variability of CO2 and CH4 in wetlands, and how these might change with changing environmental conditions and across different wetland types, is critical to understanding the current and future role of wetlands in the global carbon cycle.

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