npj Microgravity

The transcriptomic interaction between altered gravity and innate immunity remains largely unexplored. In this study, we established a novel dual-stress model combining 3g hypergravity with lipopolysaccharide (LPS) immune challenge in 5 days post-fertilization (dpf) zebrafish (Danio rerio) larvae. RNA sequencing revealed that exposure to hypergravity alone induced no differentially expressed genes (DEGs), indicating a remarkable transcriptional resilience. In contrast, the addition of an immune challenge under hypergravity conditions triggered a substantial transcriptomic response involving 2,706 DEGs. Functional enrichment analyses identified significant alterations in pathways related to immune function, development, and circadian regulation. Targeted qPCR analyses further validated the expression patterns of selected genes. These findings suggest that while zebrafish larvae can effectively tolerate hypergravity alone, the combination of gravitational and immune stressors elicits profound molecular responses. This study provides new insights into the interplay between altered gravity and innate immunity using an animal model, contributing to future strategies aimed at safeguarding astronaut health and supporting space-based aquaculture systems.

Exposure to chronic space radiation is a major health concern for long-duration missions beyond low Earth orbit. While most experimental studies simulate mission-relevant doses using acute irradiation, astronauts will experience persistent low-dose-rate exposure over months. Here, we used engineered three-dimensional (3D) mouse cortical tissue models and two-dimensional (2D) primary cortical cultures to investigate the effects of radiation dose rate on neuroglial function, inflammatory responses, and neuronal network activity. Cultures were exposed to a cumulative 0.5 Gy dose of {gamma}-radiation delivered either acutely (1 h) or chronically (166 h), with or without pretreatment using the radioprotective agent amifostine. In 3D cortical tissue models, we quantified DNA damage, astrocyte and microglia reactivity, neuronal survival, neurite morphology, and secretion of pro-inflammatory cytokines. In parallel, microelectrode array recordings were used to assess electrophysiological function in 2D neuronal networks following {gamma}-radiation or treatment with the radiomimetic drug bleomycin. Acute gamma radiation induced modest astrocyte activation, whereas chronic exposure caused limited neuroimmune alterations. Neither exposure paradigm impaired neuronal network activity, despite measurable DNA damage responses. Together, these findings indicate that neuronal function is preserved following low-dose-rate gamma irradiation while glial populations display selective sensitivity to radiation exposure.

A sustained human presence on Mars requires local production of bulk materials, particularly polymers. Prior approaches to space biomanufacturing rely on human waste streams, Earth-sourced consumables, or complex chemical infrastructure, limiting their ability to scale. Here we demonstrate production of polyhydroxyalkanoate (PHA) bioplastic from simulated 100% martian resources: regolith-derived soluble nutrients, acetate electrochemically fixed from martian atmosphere, and water. We screened 16 candidate organisms for growth in a chemically defined Mars medium and identified Cupriavidus necator H16 and Pseudomonas putida KT2440 as promising chassis organisms. Adaptive laboratory evolution totaling more than 1012 cumulative cell divisions improved both species' tolerance to high concentrations of acetate and leached regolith. The top C. necator evolved isolate, referred to as sPL.001, produced more than three-fold higher PHA titer under simulated Mars conditions compared to its parent strain. These results establish a path to polymer production on Mars where consumable mass is derived entirely from local resources, decoupling bulk material production from Earth supply chains.

Long-duration spaceflight may alter social cognition, yet the underlying biological mechanisms remain unclear. Emotion Recognition Task (ERT) performance remains stable during typical 6-month International Space Station (ISS) missions but declines markedly during the 340-day NASA Twins Study, suggesting duration-dependent vulnerability. Here, we propose the Von Economo Neuron (VEN) Fatigue Hypothesis, which posits that microgravity increases demand on VEN-associated social cognitive networks, eliciting adaptive myelination during shorter missions before compensatory mechanisms fail with prolonged exposure. To evaluate this hypothesis, we integrated evidence from rodent, human cortical organoid, astronaut plasma proteomic, and neuroimaging datasets. ISS-flown rodent frontal cortex demonstrated increased expression of myelination-related genes, while spaceflown cortical organoids exhibited changes consistent with oligodendrocyte remodeling. Astronaut plasma transcriptomics identified reproducible alterations in VEN-associated and myelination-related proteins across independent missions, and resting-state fMRI revealed transient changes in frontal insula connectivity following long-duration spaceflight. Together, these findings provide convergent evidence supporting the VEN Fatigue Hypothesis and identify adaptive myelination and VEN-associated network remodeling as candidate mechanisms underlying duration-dependent changes in social cognition during long-duration spaceflight.

Human deep-space missions face bone-kidney risks that cannot be extrapolated from six-month ISS data. We built a 12-state Ca-bone-urine-stone mechanistic ODE model and jointly calibrated its 11 physiological parameters on eight ISS targets by Bayesian identification (M0 base = 19-D; M1 extension adds a GCR-bone coupling term for parsimony testing only), then propagated the M0 posterior to four environments (ISS, Lunar subsurface, Lunar surface, Mars). Lumbar-lower BMD loss increases with mission duration and partial-gravity unloading (ISS 180 d -4.83% -> Mars 730 d -12.15%; 2^3 factorial: duration 82.9%, gravity 12.5%, GCR main effect ~ 0), whereas stone rate follows the opposite gradient (ISS 16.1 vs Mars 13.1 per 1000 person-years), reflecting weakened partial-gravity bone resorption alongside residual urinary chemistry changes. The dominant pathway thus shifts from bone-centric on the ISS to kidney-centric on Mars, where residual urinary-chemistry changes-not bone resorption-drive stone risk. The direct GCR-bone coupling term is unidentifiable at current ISS doses (DeltaWAIC = +0.0076 +/- 0.126 SE), so M0 is retained as the main inference model. Bisphosphonates provide >=84% BMD protection but leave a urinary-chemistry residual, so bisphosphonate monotherapy would underestimate Mars stone risk; potassium-magnesium-citrate combinations (RRR_RSS 51%) should therefore be added to deep-space countermeasures. A Lunar-surface 365-day mission is the earliest environment on the NASA roadmap to cross a composite RED threshold. That profile differs from the regolith-shielded 180-day case in both cumulative GCR (~69x) and duration (2x), so a shielding-specific effect cannot be isolated here; forcing the GCR coupling terms to zero leaves all four composite tiers unchanged (0/4, Supp S24), and the shielded 180-day profile is YELLOW rather than GREEN. Independent hold-out validation (Culliton 2025 60-day HDT-bedrest RCT, n=8 control arm of n=24 total) supports the M0 posterior predictive distribution on the lumbar-BMD sub-scope.

Background: Commercial spaceflight now carries civilians on short missions, yet their stress-axis physiology is poorly described. Earlier shuttle data suggest that sympathetic responses predominate after short flights and glucocorticoid responses after long ones. The neutrophil-to-lymphocyte ratio (NLR) is a low-cost readout of both. Methods: Preregistered secondary analysis of open clinical laboratory data (NASA Open Science Data Repository OSD-569 and OSD-575) from the four Inspiration4 crew members, each sampled seven times: three draws before launch, one the day after return (R+1) and three during recovery (R+45 to R+194). Log-transformed NLR was modelled with a linear mixed model with a random intercept per crew member and Kenward-Roger inference. Lymphocyte and eosinophil counts and C-reactive protein were secondary outcomes with false discovery rate correction. Results: All 28 draws were analysed. NLR at R+1 did not differ from pre-flight (fold change 1.04; 95% CI 0.81 to 1.34; p = 0.73); two crew members increased (+25% and +46%) and two decreased (-27% and -11%). During recovery NLR was 23% lower than pre-flight (fold change 0.77; 95% CI 0.64 to 0.92; p = 0.005). No secondary outcome changed after correction; lymphocytes were 18% lower at R+1 (95% CI -35% to +4%; q = 0.31). Between-person differences explained 58% of the variance. An ordinary regression ignoring repeated measures missed the recovery effect (p = 0.08). Conclusions: A 3-day orbital flight produced no consistent leukocyte stress signature one day after return. The lower NLR during recovery suggests that pre-flight values, not recovery values, deviate from the resting state, which has implications for how baselines are defined in short-duration spaceflight studies.

Human spaceflight may perturb the gut microbiota, but densely sampled short missions remain poorly characterized. We profiled 27 phase-matched fecal samples from two astronauts during an 18-day International Space Station mission and one ground-based participant following the same daily schedule using Oxford Nanopore full-length 16S sequencing. Participant identity dominated genus-level Bray-Curtis variation (R2 = 0.489, p < 0.001). In astronaut-only community analyses, mission phase explained 23.4% of genus-level (p = 0.035) and 22.3% of species-level (p = 0.021) variation. Astronauts showed greater displacement from personal baselines than B1 (0.331 versus 0.171) and 1.58-fold higher volatility. Astronaut-only taxon models identified 2 of 81 genera and 5 of 139 species; Collinsella increased from quarantine to orbit (coefficient = 2.586, q = 0.037). Thus, the short-duration spaceflight interval was accompanied by individualized, temporally localized community and taxon shifts rather than uniform microbiota restructuring.

Current planetary protection approaches rely heavily on spore-based tests developed for Mars missions and may not adequately assess contamination risks for icy ocean worlds such as Europa. We developed a genome-based framework combining deep shotgun metagenomics and supervised machine learning to predict survival-relevant microbial traits in ESA JUICE launch-site cleanrooms. From 183 genome bins, 25 representative genomes were analyzed for traits including cryotolerance, desiccation tolerance, salt resilience, anaerobic metabolism, autotrophy, and sporulation. Several skin-associated microbes carried multiple relevant traits, and some appeared actively replicating. A broader meta-analysis of 1,868 genomes showed that trait profiles vary strongly within taxa, demonstrating that taxonomy alone is insufficient for risk assessment. This framework complements current planetary protection assays, helps to predict how microbes would survive in a new biotope, and supports functional, risk-informed contamination monitoring for future space missions.

Fungal contamination poses a growing threat to spacecraft integrity, crew health, and planetary protection efforts. We describe a scalable and interpretable pipeline for identifying fungi with adaptation potential to spaceflight-associated stress conditions such as extreme temperatures, radiation levels, etc., and pathogenicity risks. Starting with proteins known to confer stress resistance, we identify orthologs across over fifteen hundred fungal species and evaluate their contamination potential via comparative proteome analysis. Our pipeline integrates proteins with known functional inference, cross-database proteome matching, and identity-based scoring to generate a ranked list of fungal species of concern. We apply this approach to detections from spacecraft assembly facilities, highlighting species with combined stress-tolerance and pathogenic potential. This study establishes a foundation for future AI-based risk assessments that can scale to orders of magnitude more fungal species, thus laying the foundation for systematic identification and assessment of fungal contaminants with potential adaptation and pathogenicity risks in spaceflight environments, thereby supporting contamination control strategies for future space missions. We also present an interactive visual online tool for researchers to trivially check the contamination potential of species in their own samples.

To reduce health risks for human space exploration, it is important to model the effects of deep-space radiation on biological systems. The budding yeast Saccharomyces cerevisiae is a common model organism in space radiobiology, but little is known about how radiation damage to individual cells translates into the population-level effects that experiments measure. The Agent-Based Model for Microbial Populations Exposed to Radiation (AMMPER) is a spatially explicit agent-based model that simulates the effects of ionizing radiation on S. cerevisiae cells and produces population-level results. Its goal is to improve experiment design and data interpretation. AMMPER-1 demonstrated that agent-based simulations can qualitatively reproduce the effects of proton radiation on the growth rate of wild-type and DNA-repair mutant yeast. Here, we present AMMPER-2, which addresses limitations of the first model and expands its capabilities. AMMPER-2 incorporates the dynamics of the redox dye alamarBlue, a data type commonly generated in spaceflight microbiology experiments, and models the fate of reactive oxygen species in more detail. It also adds an improved graphical interface and runs faster. AMMPER-2 remains easy to execute in Python on a standard personal laptop, providing space biologists a tool to explore experimental conditions, generate hypotheses, and interpret data from microbial space radiation experiments.

Undersea and high-altitude operations regularly put operators at risk for decompression sickness (DCS), which is attributed to bubble formation and growth during decompression. DCS mitigation strategies are validated with empirical testing, often conducted in hyperbaric chambers, which provide precise control of the pressure-time profile. A degree of variability for study outcome is anticipated in both decompression sickness (DCS) and venous gas emboli (VGE) endpoints. Experimentation in a chamber offers precision, but is not always practical or operationally relevant, leading researchers to use open water for the dive exposure. Dive profile consistency may vary by diver skill level and environmental conditions, potentially introducing dive profile deviations, which may be a factor of individual variability. There does not exist a quantitative framework for evaluating dive profile consistency and quantifying deviations in open water studies. In this work, we evaluate existing dive profile metrics and propose a workflow to estimate dive profile deviations using the Buhlmann dissolved gas phase model. The dive profile metrics included depth and time-based calculations, as well as surface gradient factor, degree-of-conservatism and the root mean square error of the Buhlmann tissue compartments. We developed a set of simulated dive profiles and obtained a set of 40 open water dives previously collected by certified divers, both of which were used to evaluate performance of the dive profile metrics. Depth and time-based metrics offered sensitivity to varying depths and time durations of the dive profiles, respectively. For the field dives, we found the Buhlmann root mean square error metric performed best at identifying the deviation profile, followed by pressure root time. These evaluations demonstrate the utility and limitations of previously published dive profile metrics and emphasize the importance of accounting for dive profile consistency in open water decompression trials.

Simulated microgravity provides a controlled perturbation for testing how loss of mechanical load affects human tissues. After 24 hours in rotating-wall vessels, neural, cardiac and tonsil organoids developed tissue-specific transcriptional responses that overlapped published spaceflight datasets, accompanied by higher transcriptomic-age estimates in neural and cardiac models, altered cardiac-organoid contraction dynamics and modified tonsil-organoid antiviral gene-expression signatures. These findings establish a multi-organoid framework for studying acute responses to gravitational unloading.

The nearshore marine benthos in McMurdo Sound is one of the best-studied high Antarctic marine ecosystems, yet multiparameter environmental datasets that describe both seasonal and geographic variation in key environmental parameters are lacking. We installed oxygen, temperature, and conductivity loggers at nearshore shallow benthic sites around McMurdo Sound to obtain a high-resolution year-long record of these parameters in 2021 and 2022. Our data showed that benthic organisms experienced a suite of seasonal changes, particularly in temperature and oxygen saturation, that had potential to significantly impact physiology. High summer temperatures were always accompanied by high oxygen saturations, which could provide a metabolic refuge for Antarctic benthic organisms whose oxygen demand increases strongly with temperature. Temperature and oxygen also fluctuated rapidly; on a timeframe of hours to days, these fluctuations sometimes spanned nearly the entire range of seasonal variability. Climate-driven changes to the Southern Ocean are likely to lead to increased seasonal warming, freshening, and potentially deoxygenation, and understanding the extent and rate of change that benthic organisms currently experience will be important to predicting their responses to future conditions.

Life evolved under broad spectrum sunlight (300-2500nm), but in the modern built environment under standard Light Emitting Diode (LED) illumination is restricted to around 400-650nm. Different wavelengths influence metabolism via mitochondria. 670-900nm support mitochondrial function while those in the Soret band (420-450nm) undermine mitochondrial ability. Under LED lighting, metabolism is challenged with reduced mitochondria ability, and hence, reduced demand for blood sugars that are required to produce adenosine triphosphates (ATP). As longer wavelengths enhance mitochondrial performance, they increase demand for blood sugars, reducing serum glucose. Here we change the lighting in windowless offices providing either standard LED desk lamps or those supplemented with 850nm in real-world environments. This was for two hours every morning over three days. We then assessed blood sugars with two independent methods, an oral glucose tolerance test and continuous glucose monitoring. Subjects exposed to standard LEDs had significantly increased blood sugars, while those exposed to lamps with added 850nm had significantly reduced blood sugars. These real-world data highlight the importance of light in controlling metabolism. They raise issues concerning public health in interior environments where we now spend >90% of our lives.

To better understand how animals cope with increasingly variable and challenging environments, there is a need to study how prolonged exposure to elevated glucocorticoid hormones (i.e. one mediator of the stress response) affects their physiology. While glucocorticoid elevation is known to increase oxidative stress and accelerate cellular ageing, there is evidence that king penguins (Aptenodytes patagonicus) can prevent oxidative stress during acute stress exposure, suggesting that species may differ in their sensitivity to glucocorticoids downstream negative effects. As king penguins thrive in a seemingly harsh environment, we hypothesized that they may be able to limit the deleterious effects usually associated with chronic glucocorticoid elevation, either through resistance (i.e. prevention of downstream negative effect) or resilience (i.e. rapid recovery following transient negative effect). To test this hypothesis, we experimentally elevated corticosterone levels in incubating king penguins and quantified treatment effects on a suite of physiological traits at multiple time points across incubation and early chick-rearing, up to ca. 2 months after implantation. Corticosterone-treated individuals showed a prolonged increase in corticosterone and decrease in body condition, confirming our treatment likely mimicked sustained stress exposure. Heterophil-to-lymphocyte ratio was only increased transiently, and there was no clear evidence that treatment influenced oxidative stress or telomere length maintenance. Plasma energy metabolites were mainly affected early after implantation, with rapid recovery over time. Overall, our results suggest that adult king penguins show at least moderate resistance and resilience to chronic corticosterone elevation, especially in preventing cellular integrity loss, though at-sea physiological effects remain to be determined.

Meteorite impact structures on earth represent unique terrestrial analogues of extreme planetary environments where fractured lithologies, hydrothermal alteration, elevated concentrations of radionuclides, and prolonged water-rock interactions create ecological niches for specialized microbial communities. The Palaeoproterozoic Dhala impact structure in north-central India is characterized by uranium-bearing impactites and possesses a very high concentration of Uranium (up to 99.5 ppm) that makes it a unique natural laboratory to investigate microbial adaptation to radioactive and metal-rich geological environments. In addition, the Dhala structure harbors specialized radiotoxic hydrothermal mineral phases such as coffinite and pitchblende, which show a globally distinct and biologically unexplored niche. The present investigation is the first in-depth, whole-genome metagenomic study of soil and water samples of uranium-rich sites from the Dhala structure, exploring the whole microbial community (Bacteria, Archaea, Eukaryotes, and Viruses) up to the species level present in the samples. The cross-domain metagenomics analysis identified a highly unique and resilient microbiome that consists of bacteria, archaea, eukaryotes, and viruses, coevolved under prolonged radiological and multiple metal stress. Functional metagenomic analysis revealed numerous metabolic adaptations responsible for their survival, homeostasis, and biomineralization in situ. The deep sequencing method further enabled the identification of 58 functional genes directly involved in uranium bioremediation. Furthermore, this study revealed important pathways for radionuclide reduction, cellular efflux, and biotransformation. Novel findings of the present study point out the in-depth evolutionary relations of biosphere-geosphere interaction within an ancient hypervelocity impact-generated ecosystem. In a nutshell, the Dhala extremophiles with novel genetic makeup present an untapped and promising reservoir for the development of eco-friendly, next-generation microbial bioremediation strategies to efficiently tackle the global anthropogenic contamination of uranium and the challenges of nuclear waste management. Thus, the present study establishes Dhala structure as an unparalleled site for environmental geomicrobiology, microbial evolution, and astrobiology.

Despite being a topic of early experimental studies, the effects of immersion-emersion cycles and temperature on the heart rate of intertidal Mytilus mussels have not been fully characterized. Using a recently released intertidal chamber paired with our own software package, we conducted a multiday experiment and continuously monitored the heart rate of the blue mussel Mytilus edulis. Under normal conditions, we detected a subtle spike in heart rate upon emersion before the eventual decline, as well as an overshoot upon reimmersion. Additionally, heart rate was sensitive to temperature changes during immersion but less responsive during emersion. These patterns were markedly altered following an unintended prolonged emersion event, which led to the loss of the emersion spike, an extended reimmersion overshoot, and heightened thermal sensitivity on top of an overall elevation in heart rate. However, the heart rate gradually returned to the pre-event baseline over the following days, demonstrating the significant resilience of the mussels. Our study highlights the potential of high-resolution physiological data in assessing the effects of environmental stressors on coastal ecosystems.

Long-duration spaceflight is known to disrupt several aspects of immune function yet its impact on the antiviral antibody repertoire remains unclear. We analyzed longitudinal plasma samples from 11 astronauts participating in a 6-month long spaceflight, including preflight, inflight, and postflight timepoints. Using a high-throughput serological method based on phage display of linear peptides from thousands of viruses we assessed the stability of antiviral antibodies over time. Across two phage libraries expressing different pathogen panels, we detected antibodies against Alphainfluenzavirus, Betainfluenzavirus, Enterovirus, and Orthopneumovirus consistently with the highest abundancy in all astronauts over all timepoints. Antibody levels against these infectious agents remained remarkably stable within individuals during and after spaceflight. In contrast, substantial heterogeneity was observed among astronauts, reflecting individualized immune histories and baseline antibody profiles. These results were confirmed by a different immunoassay using whole protein from the most targeted viruses. Together, these findings demonstrate that the antiviral antibody repertoire is largely resilient during prolonged spaceflight, highlighting preserved humoral memory despite potential dysregulation in cellular immune compartments.

Intertidal mudflats hosting diatom-dominated microphytobenthic communities experience strong variability in environmental conditions, which can lead to cellular oxidative stress. These constraints can, in some cases, affect diatom metabolism and photosynthetic performance in the short term, potentially compromising their survival and even leading to cell death. This study investigates pigment, isoprostanoid, and photophysiological changes in a diatom assemblage originating from a natural microphytobenthic biofilm under different durations of helium-oxygen bubbling cold atmospheric plasma experimental treatments, mimicking complex oxidative conditions of the environment. To this end, 2-min and 5-min treatments were applied to the diatom assemblage, and metabolic parameters were monitored over time up to +180 min after plasma treatment cessation. Despite physicochemical changes and slight perturbations in metabolite profiles induced by plasma treatments, photosynthetic capacities of the diatoms remained largely preserved. The duration-dependent effects of plasma treatments induced selective and mostly reversible changes, primarily characterized by an increase in the relative proportions of pheopigments and a decrease in the relative proportions of {beta}-carotenes following the 5-min treatment. A transient decrease in the relative proportions of the isoprostanoids 10-F4t-neuroP and 5-F2t-IsoP was also observed. By exposing natural diatom assemblage to plasma-generated oxidative conditions, this study provides novel insights into how marine microbiome respond to oxidative perturbations, contributing to our understanding of diatom success in fluctuating intertidal environments.

Despite the well-known health risks of neutron exposures, key gaps remain in understanding neutron-induced molecular responses and identifying reliable biodosimetric markers that distinguish neutrons from photon exposure. We provide the first genome-wide analysis of the human blood transcriptional response to an accelerator-derived fission-like spectrum of neutrons versus photons, evaluating transcriptomic relative biological effectiveness (RBE) and radiation quality-discriminating gene signatures. Whole blood from healthy donors was irradiated ex vivo with X-rays (140 kV, 0-4 Gy, n = 3) or neutrons (0.1-8 MeV, 0-1 Gy, n = 2), incubated for 6 h or 24 h, and processed for RNA sequencing from peripheral blood mononuclear cells (PBMCs). Neutrons were markedly more potent than X-rays at inducing differentially expressed genes (DEGs) at equal doses, showing a peak response 6 h post-irradiation followed by a decline. In contrast, X-rays caused a continuous increase in DEGs up to 24 h (neutrons vs. X-rays at 1 Gy: 1,449 vs. 121 DEGs at 6 h; 996 vs. 621 DEGs at 24 h). A universal p53-centered 34-gene signature, including FDXR, EDA2R, GADD45A, and ZMAT3, showed highly monotonic dose responses (Spearman correlation coefficient {approx} 1) across donors, radiation qualities, and timepoints. Additionally, difference-in-differences analysis identified radiation quality-discriminating genes only at 6 h, with transcriptional convergence observed by 24 h, suggesting a very narrow time window for biodosimetric differentiation. We identified a neutron-specific gene signature driven by cGAS-STING-NF-{kappa}B signaling (RELB, NFKB1, C3, MALAT1) and suppression of B-cell and myeloid identity genes (IGHD, TCL1A, CLEC7A, TLR2), defining a biologically coherent neutron quality index with distinct immunomodulatory effects. For the first time, we assessed neutron RBEs at the gene, pathway, and global transcriptomic levels in a human blood model, reporting a global transcriptomic neutron RBE of 1.30 (95% CI: 1.14-1.49) at 6 h and 1.21 (95% CI: 1.14-1.28) at 24 h, providing a valuable basis for biodosimetry in mixed-field exposure scenarios. Our findings advance the mechanistic understanding of neutron radiation responses and support the development of biodosimetric approaches for mixed-field exposure scenarios.