Low Oxygen Availability Research Articles

Acute Hypobaric Hypoxia Causes Alterations in Acetylcholine-Mediated Signaling Through Varying Expression of Muscarinic Receptors in the Prefrontal Cortex and Cerebellum of Rats' Brain.

Sharma, Narendra Kumar, Mansi Srivastava, Tikam Chand Dakal, Vipin Ranga, and Pawan Kumar Maurya. Acute hypobaric hypoxia (HH) causes alterations in acetylcholine-mediated signaling through varying expression of muscarinic receptors in the PFC and cerebellum of rats' brain. High Alt Med Biol. 00:00-00, 2024. Background: Muscarinic receptor (CHRM) proteins are G-protein-associated acetylcholine receptors found in neuronal membranes. Five major subtypes, CHRM1-CHRM5, modulate acetylcholine in central nervous system signaling cascades. CHRM1, CHRM3, and CHRM5 are linked to Gαq/Gα11 proteins, whereas CHRM2 and CHRM4 are linked to Gαi/Gαo proteins. Objective: Limited research has been conducted to explore the impact of HH on CHRM gene expressions. It is caused by low oxygen availability at high altitudes, which impairs neurotransmission, cognitive performance, and physiological functions. Previous studies have shown that exposure to hypoxia leads to a reduction in CHRM receptors, which in turn causes alteration in signal transduction, physiological responses, cognitive deficits, and mood alterations. Method: In the present study, we have used semiquantitative PCR to measure muscarinic receptor gene expression after 6, 12, and 24 hours of HH exposure at 25,000 feet using a decompression chamber in rat brain's PFC and cerebellum. Result: We have found that CHRM1-CHRM5 downregulated after acute exposure to hypoxia until 12 hours, and then, the expression level of these receptors increased to 24 hours when compared with 12 hours in PFC. All subtypes have shown a similar pattern in PFC regions under hypoxia exposure. On the other hand, these receptors have shown altered expression at different time points in the cerebellum. CHRM1 and CHRM4 acutely downregulated, CHRM2 and CHRM5 downregulated, while CHRM3 upregulated after hypoxia exposure. Conclusion: Our study, for the first time, has shown the altered expressions of muscarinic receptors under temporal hypoxia exposure. The altered expression pattern has shown an association with acclimatization and protection against necrosis due to hypoxia. This study may pave further investigations for understanding and addressing the cognitive, behavioral, and physiological impacts of hypoxia and therapeutic development.

Synergy of exercise and hypoxia for brain health and aging – A narrative review

Regular exercise is a well-established means to improve brain health and prevent age-related neurological diseases, including dementia (Marques-Aleixo et al., 2020). The precise mechanisms how direct exercise effects are transmitted to the brain remain incompletely understood. However, the increased oxygen demand and associated metabolic stress in the primarily affected tissues – the working skeletal muscle, the cardiovascular and the respiratory system – likely play crucial roles in exercise-signalling to the brain (Severinsen & Pedersen, 2020). Besides the mobilization of beneficial circulating factors, the modulation of blood properties and blood-flow, the immune system and the autonomous system are involved. Intriguingly, physiological stress induced by low environmental oxygen availability (hypoxia) can induce the activation of similar processes like exercise. The aim of this contribution is to evaluate the role of hypoxia in the benefits of exercise on the brain. Accumulating evidence demonstrates the potential of direct modulation of inspired oxygen levels to improve neurological diseases (Burtscher et al., 2021). Reduced all-cause mortality in people living at moderate altitudes (and therefore in chronic, mild hypobaric hypoxia) may also be associated with reduced risk of neurological diseases, including of stroke (Faeh et al., 2009). This is surprising, because the hypoxic stress at moderate altitudes (usually defined as altitudes between 1,500 and 2,500 m) is generally considered too low to induce substantial hypoxia adaptations. It is thus possible that the combination of moderate environmental hypoxia at moderate altitude with the increased oxygen demand during exercise is required to promote protective adaptations, such as of the brain. Considering this possibility, synergistic and complementary molecular and systemic responses and adaptations to exercise and hypoxia may benefit the brain. Among the involved molecular processes are mitochondrial changes following cellular stress that are also linked to the regulation of adaptations by the transcription factor hypoxia inducible factor, which is activated by both hypoxia and exercise. Mitochondria are the main molecular oxygen consumers, respond sensitively to stress and dispose of a wide array of intra- and intercellular communication modes (Memme et al., 2021). Moreover, exerkines, blood-borne factors released in response to exercise, have emerged as important mediators of inter-organ exercise-signalling (Severinsen & Pedersen, 2020) and modulate the autonomic and immune system in response to hypoxic and metabolic stress. In conclusion, the activation of endogenous responses to hypoxic and metabolic stress are powerful means to improve brain health and healthy aging. Based on the overlapping and distinct physiological responses to hypoxia and exercise, brain benefits of exercising at higher altitudes and advances in the development of customized strategies to improve brain resilience are promising approaches to target neurological diseases. While the safe performance of exercise in moderate altitudes is already considered an impactful way to improve brain health, the optimization of combined exercise and (artificially induced) hypoxia for specific target groups requires further in-depth investigation. References Burtscher, J., Mallet, R. T., Burtscher, M., & Millet, G. P. (2021). Hypoxia and brain aging: Neurodegeneration or neuroprotection? Ageing Research Reviews, 68, Article 101343. https://doi.org/10.1016/j.arr.2021.101343 Faeh, D., Gutzwiller, F., Bopp, M., & Group, S. N. C. S. (2009). Lower mortality from coronary heart disease and stroke at higher altitudes in Switzerland. Circulation, 120(6), 495-501. https://doi.org/10.1161/CIRCULATIONAHA.108.819250 Marques-Aleixo, I., Beleza, J., Sampaio, A., Stevanović, J., Coxito, P., Gonçalves, I., Ascensão, A., & Magalhães, J. (2020). Preventive and therapeutic potential of physical exercise in neurodegenerative diseases. Antioxidants & Redox Signaling, 34(8), 674–693. https://doi.org/10.1089/ars.2020.8075 Memme, J. M., Erlich, A. T., Phukan, G., & Hood, D. A. (2021). Exercise and mitochondrial health. The Journal of Physiology, 599(3), 803-817. https://doi.org/10.1113/jp278853 Severinsen, M. C. K., & Pedersen, B. K. (2020). Muscle-organ crosstalk: The emerging roles of myokines. Endocrine Reviews, 41(4), 594-609. https://doi.org/10.1210/endrev/bnaa016

Microorganisms in beet sugar production – perspective on technological opportunities and risks

The sugar industry has long faced challenges from microorganisms during production. Preventing sugar losses and microbial-related issues such as the formation of organic acids, gases like CO2 or H2, or slimy substances continues to be key concerns. Fortunately, process parameters such as high temperatures, low pH values and limited oxygen availability create unfriendly conditions for microorganisms, and antimicrobial agents have been developed to control microbial growth. However, a proactive approach would utilize the advantageous properties of microorganisms to break down undesirable substances and promote desirable ones. For example, acidic by-products from bacterial metabolism lower the pH and thus stabilize sugar beet cossettes during pressing. Additionally, beneficial metabolic processes have been recognized, such as preferentially utilizing monosaccharides instead of sucrose or selectively degrading undesired substances (e.g., converting nitrite into elemental nitrogen). Modern sequencing techniques continue to identify unknown bacteria with the potential to improve the process. Exploring these bacteria could offer valuable insights for a better microorganism management in beet sugar production. This perspective article discusses the microbial diversity in beet sugar factories and strategies for better utilization of microbial benefits, aiming for sustainable improvements in sucrose extraction. However, extensive research is necessary to identify and characterize suitable bacterial species and how best to exploit them.

Mechanistic Insights and Genetic Approaches for Enhancing Submergence Tolerance in Rice

Rice, a pivotal staple crop, serves as a dietary foundation for approximately half of the global population. Its cultivation, traditionally reliant on submerged conditions, faces significant challenges due to sudden flooding events. The majority of rice varieties are highly sensitive to prolonged submersion beyond a mere seven days, resulting in substantial yield losses. As global climate patterns shift, the occurrence and intensity of flooding are predictable to increase, exacerbating this issue. Therefore, development of rice varieties having enhanced submergence tolerance is critical to sustaining productivity and ensuring food security in flood-prone regions. Understanding the physiological and biochemical mechanisms underlying submergence tolerance is crucial in this context. Key physiological mechanisms include the regulation of carbohydrate reserves for energy during low oxygen availability, ethylene-responsive factors, especially the Sub1A gene to, regulate growth and stress responses, curbing excessive elongation to conserve energy and enhance survival. Additionally, specialized tissues such as aerenchyma and adventitious roots improve oxygen transport and nutrient uptake under flooded conditions. Genetic approaches, including Marker-Assisted Selection (MAS), have been instrumental in the development of submergence-tolerant rice varieties. The integration of the Sub1 QTL, especially the Sub1A gene, into high-yielding rice varieties has led to significant advancements in breeding submergence-tolerant cultivars. These genetic improvements provide a promising solution to mitigate the detrimental effects of flooding on rice production, ensuring the stability and sustainability of this essential crop in the face of changing climate conditions. This review discusses various mechanisms adapted by rice and genetic advancements aimed at enhancing submergence tolerance in rice to secure food production for future generations.

Flying to high-altitude destinations.

Every year millions of people fly to high-altitude destinations. They thereby expose themselves to specific high-altitude conditions. The hypoxic environment (low ambient oxygen availability) constitutes a major factor affecting health and well-being at high altitude. While the oxygen availability is already moderately reduced inside the aircraft cabin, this reduction becomes aggravated when leaving the plane at high-altitude destinations. Especially if not pre-acclimatized, the risk of suffering from high-altitude illnesses, e.g., acute mountain sickness, high-altitude cerebral or pulmonary edema, increases with the level of altitude. In addition, diminished oxygen availability impairs exercise tolerance, which not only limits physical activity at high altitude but may also provoke symptomatic exacerbation of pre-existing diseases. Moreover, the cold and dry ambient air and increased levels of solar radiation may contribute to adverse health effects at higher altitude. Thus, medical pre-examination and pre-flight advice, and proper preparation (pre-acclimatization, exercise training, and potentially adaptation of pharmacological regimes) are of utmost importance to reduce negative health impacts and frustrating travel experiences.

Characterization and gene expression profiles of Cilus gilberti leptin in response to culture parameters

The Chilean meagre, Cilus gilberti, emerges as a novel species to South American aquaculture. Nevertheless, the successful establishment of its cultivation necessitates careful consideration of productive parameters and tolerance to abiotic stressors. To address these challenges, the identifications of biomarkers emerges as a promising approach. Indeed, leptin stands out as a potential biomarker, given its multifaceted role. This study focuses on characterizing leptin in C. gilberti (cgLep) and assessing its gene expression in juveniles exposed to different culture and feeding conditions. The results indicated that cgLep coding sequence yields a 137-amino acid prohormone, preserving high relevant cysteine residues for maintaining its structural integrity. Basal cgLep gene expression profiles reveal its expression mainly in the liver, followed by white muscle. Conversely, its receptor (cgLepR) exhibits higher levels in white muscle. Additionally, it was observed that juveniles in a postprandial state exhibited an upregulation of hepatic cgLep. Simultaneously, the cgLepR showed a significant increase at brain level during the preprandial stage. The exposure to acute hypoxia revealed a notable upregulation of cgLep after two hours of low oxygen availability and returned to normoxia baseline after six hours post-hypoxia. Notably, when subjected to a prolonged daily hypoxia regimen, no significant differences in leptin mRNA expression were observed. This suggests a dynamic adaptive response of the C. gilberti leptin system to hypoxia. Finally, juvenile Chilean meagre cultivated at 15 Kg/m3 showcase significant individual variability in hepatic leptin expression levels when compared to those cultured at 25 or 35 kg/m3. These observations highlight that leptin primarily expresses in the liver and its expression is notably influenced by fasting periods and chronic stress induced by low stock density. This variability in leptin expression could potentially impact food intake, emphasizing the importance of considering these factors in the design and implementation of aquaculture practices for Chilean meagre.

Protective Effects of Velvet Antler Methanol Extracts on Hypoxia-Induced Damage in Caenorhabditis elegans through HIF-1 and ECH-8 Mediated Lipid Accumulation.

Velvet antler, a traditional tonic widely used in East Asia for its health benefits, is explored in this study for its protective effects against hypoxia-induced damage using Caenorhabditis elegans (C. elegans) as a model. Hypoxia, characterized by low oxygen availability, induces significant physiological stress and potential tissue damage. Our research demonstrates that methanol extracts from velvet antler (MEs) enhance the survival of C. elegans under hypoxic conditions. This enhancement is achieved through the stabilization of hypoxia-inducible factor-1 (HIF-1) and the promotion of lipid accumulation, both of which are crucial for mitigating cellular damage. Specifically, MEs improve mitochondrial function, increase ATP production, and aid in the recovery of physical activity in C. elegans post-hypoxia or following hypoxia-reoxygenation (HR). The pivotal role of HIF-1 is underscored by the loss of these protective effects when HIF-1 function is inhibited. Additionally, our findings reveal that the gene related to lipid metabolism, ech-8, significantly contributes to the lipid accumulation that enhances resilience to hypoxia in C. elegans treated with MEs. These results not only highlight the therapeutic potential of velvet antler in modern medical applications, particularly for conditions involving hypoxic stress, but also provide insights into the molecular mechanisms by which MEs confer protection against hypoxic damage.

Short communication: Maintained visual performance in birds under high altitude hypoxia

Birds are highly dependent on their vision for orientation and navigation. The avian eye differs from the mammalian eye as the retina is avascular, leaving the inner, highly metabolically active layers with a very long diffusion distance to the oxygen supply. During flight at high altitudes, birds face a decrease in environmental oxygen partial pressure, which leads to a decrease in arterial oxygen levels. Since oxygen perfusion to the retina is already limited in birds, we hypothesize that visual function is impaired by low oxygen availability. However, the visual performance of birds exposed to hypoxia has not been evaluated before. Here, we assess the optomotor response (OMR) in zebra finches under simulated high-altitude hypoxia (10%) and show that the OMR is largely maintained under hypoxia with only a modest reduction in OMR, demonstrating that birds can largely maintain visual function at high altitudes. The method of our study does not provide insight into the mechanisms involved, but our findings suggest that birds have evolved physiological mechanisms for retinal function at low tissue oxygen levels.

Declining glacier cover drives changes in aquatic macroinvertebrate biodiversity in the Cordillera Blanca, Perú.

Ongoing climate change threatens the biodiversity of glacier-fed river ecosystems worldwide through shifts in water availability and timing, temperature, chemistry, and channel stability. However, tropical glacier-fed rivers have received little attention compared to those in temperate and Arctic biomes, despite their unique biodiversity potentially responding differently due to additional stress from higher altitude locations thus lower oxygen availability, diurnal freeze-thaw cycles, and annual monsoon rainfall disturbances. However, tropical glacier-fed rivers have received little attention compared to those in temperate and Arctic biomes, despite their unique biodiversity potentially responding differently due to additional stress from higher altitude locations thus lower oxygen availability, diurnal freeze-thaw cycles, and annual monsoon rainfall disturbances. This study quantified aquatic biodiversity responses to decreasing glacier cover in the Cordillera Blanca range of the Peruvian Andes. Ten rivers were studied along a gradient of decreasing glacier cover in the Parón, Huaytapallana, and Llanganuco basins, with a specific focus on macroinvertebrates and physicochemical parameters in both the dry and wet seasons. We found higher temperatures, more stable and lower turbidity rivers as glacier cover decreased, which were related significantly to higher local diversity and lower β-diversity. Analysis of similarity revealed significant differences in the macroinvertebrate community among rivers with high, medium, or low glacier cover, illustrating turnover from specialists to generalists as glacial influence decreased. Redundancy analysis demonstrated that there were more species found to prefer stable beds and water temperatures in medium and low glacier cover in a catchment rivers. However, certain taxa in groups such as Paraheptagyia, Orthocladiinae, Anomalocosmoecus, and Limonia may be adapted to high glacial influence habitats and at risk of glacier retreat. Although species composition was different to other biomes, the Cordillera Blanca rivers showed similar benthic macroinvertebrate biodiversity responses to glacier retreat, supporting the hypothesis that climate change will have predictable effects on aquatic biodiversity in mountain ranges worldwide.

Metabolic recovery from submaximal exercise in hypoxia acclimated high altitude deer mice (Peromyscus maniculatus)

Animals living at high-altitude are faced with unremitting low oxygen availability. This can make it difficult to perform daily tasks that require increases in aerobic metabolism. An activity important for survival is aerobic locomotion, and the rapid recovery of muscle metabolism post exercise. Past work shows that hypoxia acclimated high-altitude mice (Peromyscus maniculatus) have a greater reliance on carbohydrates to power exercise than low altitude mice. However, it is unclear how quickly after aerobic exercise these mice can recovery and replenish muscle glycogen stores. The gastrocnemius muscle of high-altitude deer mice has a more aerobic phenotype and a greater capacity to oxidize lipids than low altitude deer mice. This suggests that high altitude mice may recover more rapidly from exercise than their lowland counterparts due to a greater capacity to support glycogen replenishment using intramuscular triglycerides (IMTG). To explore this possibility, we used low- and high-altitude native deer mice born and raised in common lab conditions and acclimated to chronic hypoxia. We determined changes in oxygen consumption following 15 min of aerobic exercise in 12% O2 and sampled skeletal muscles and liver at various time points during recovery to examine changes in key metabolites, including glycogen and IMTG. We found depletion in glycogen stores during exercise only in lowlanders, which returned to resting levels following 90 min of recovery. In contrast, IMTG did not change significantly with exercise or during recovery in either population. These data suggest that exercise recovery is influenced by altitude ancestry in deer mice.

Hypoxia-associated markers in the prognosis of oral canine melanoma.

Canine oral malignant melanoma (COMM) is the most common neoplasm in the oral cavity characterized by local invasiveness and high metastatic potential. Hypoxia represents a crucial feature of the solid tumor microenvironment promoting cancer progression and drug resistance. Hypoxia-inducible factor-1α (HIF-1α) and its downstream effectors, vascular endothelial growth factor A (VEGF-A), glucose transporter isoform 1 (GLUT1), C-X-C chemokine receptor type 4 (CXCR4), and carbonic anhydrase IX (CAIX), are the main regulators of the adaptive response to low oxygen availability. The prognostic value of these markers was evaluated in 36 COMMs using immunohistochemistry. In addition, the effects of cobalt chloride-mediated hypoxia were evaluated in 1 primary COMM cell line. HIF-1α expression was observed in the nucleus, and this localization correlated with the presence or enhanced expression of HIF-1α-regulated genes at the protein level. Multivariate analysis revealed that in dogs given chondroitin sulfate proteoglycan-4 (CSPG4) DNA vaccine, COMMs expressing HIF-1α, VEGF-A, and CXCR4 were associated with shorter disease-free intervals (DFI) compared with tumors that were negative for these markers (P = .03), suggesting hypoxia can influence immunotherapy response. Western blotting showed that, under chemically induced hypoxia, COMM cells accumulate HIF-1α and smaller amounts of CAIX. HIF-1α induction and stabilization triggered by hypoxia was corroborated by immunofluorescence, showing its nuclear translocation. These findings reinforce the role of an hypoxic microenvironment in tumor progression and patient outcome in COMM, as previously established in several human and canine cancers. In addition, hypoxic markers may represent promising prognostic markers, highlighting opportunities for their use in therapeutic strategies for COMMs.

The roles of seagrass litter decomposition in determining blue carbon sink capacity

AbstractSeagrass litter is a crucial autochthonous source of sediment organic carbon (Corg) that contributes to Corg storage in coastal ecosystems. However, our understanding of seagrass litter decomposition effects on sediment Corg sequestration and the factors influencing the capacity for autochthonous carbon sequestration remains limited. We investigated Zostera marina litter decomposition dynamics in eelgrass meadows along the Korean coast by monitoring changes in the remaining litter mass and autochthonous Corg during the decomposition process. We used a double‐component exponential decay models to characterize the decomposition dynamics and estimate the autochthonous Corg remaining. We also identified potential factors affecting litter decay and Corg accumulation in sediments by examining site‐specific physicochemical properties. Our findings revealed that double‐component models effectively characterized litter decomposition dynamics and indicated greater preservation of litter‐derived slowly degrading Corg in sediments. The reduced decomposition of litter materials owing to low oxygen availability in the muddy sediments led to greater retention of litter mass and litter‐derived Corg in sediments. The anoxic conditions of below‐ground litterbags, compared with above‐ground litterbags, could be alleviated by the oxygen transport through fresh Z. marina roots, thereby potentially stimulating the microbial decomposition of Z. marina below‐ground litter materials at these sites. Our findings highlight the importance of understanding litter decomposition dynamics to accurately assess the carbon sink capacity of seagrass meadows, and demonstrate that physicochemical properties can influence seagrass litter decomposition.

Abstract 370: BACH1 metastatic activity is regulated by oxygen-dependent proline hydroxylation in triple-negative breast cancer

Abstract Hypoxia, low oxygen availability at the tissue level, is a key driver of metastasis in solid tumors. Oxygen-sensitive activation of hypoxia-induced transcription factors is in part regulated by prolyl hydroxylase domain proteins (PHDs). We and others previously showed that the BTB and CNC homolog 1 (BACH1) transcription factor promotes metastasis in various cancer types. In accompanying work, we show that BACH1 is prolyl-hydroxylated and degraded in an oxygen-dependent manner in triple-negative breast cancer (TNBC). Here we show that BACH1 lacking its hydroxylated proline sites (i.e., mutant BACH1) expressed in TNBC cells exhibits increased DNA binding to a canonical BACH1 binding site as well as greater transcriptional output of metastasis and hypoxia-response-related genes relative to wild-type BACH1. Furthermore, in vivo assays showed that mutant BACH1 promotes greater tumor metastasis of TNBC cells than wild-type BACH1. Our findings suggest that the proline hydroxylation of BACH1 directly regulates BACH1’s transcriptional activity by modulating its DNA-binding activity. Together, these results reveal a mechanism underlying oxygen-sensitive regulation of BACH1 that could potentially contribute to BACH1-mediated pro-metastatic signaling and therapeutic resistance under hypoxia in TNBC. Citation Format: Thomas Li, Long Chi Nguyen, Christopher Dann, Madeline Henn, Dongbo Yang, Emily Shi, Lydia Robinson-Mailman, Kazuhiko Igarashi, Marsha R. Rosner. BACH1 metastatic activity is regulated by oxygen-dependent proline hydroxylation in triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 370.

Ecosystem impacts of an invasive charophyte (Nitellopsis obtusa) interpreted in a multiple stressor context using paleolimnology

Korosi JB, Adano RC, Do PHP, Hall RI, Jeyarajah J, Stewart EM, Wiklund JA, Thienpont JR. 2024. Ecosystem impacts of an invasive charophyte (Nitellopsis obtusa) interpreted in a multiple stressor context using paleolimnology. Lake Reserv Manage. 40:132–144. Proliferation of Nitellopsis obtusa (starry stonewort), an aquatic invasive macroalga, is an emerging water quality concern in North America, but disentangling its effects is complicated by multiple stressors and a lack of long-term data. In this study, we investigated the potential impacts of N. obtusa on benthic oxygen depletion and the lower food web of Lake Scugog (southern Ontario, Canada) in a multiple-stressor context through a paleolimnological assessment of ecosystem changes up to the invasion and proliferation of N. obtusa. Results reveal that myxoxanthophyll, a pigment produced by colonial cyanobacteria, was no longer detected in the sediments after the early 1990s despite being prevalent throughout the earlier history of Lake Scugog. This indicates that recently documented blooms of Microcystis, which have been hypothesized to be unprecedented and facilitated by N. obtusa, are not a new phenomenon but instead may represent a resurgence in cyanobacteria production following a period of water quality improvement. Sediment cores also documented increased relative abundance of Chironomidae taxa associated with low benthic oxygen availability after about 1920, while changes in subfossil diatom assemblage provided evidence of increased frequency and/or duration of thermal stratification indicative of climate warming effects. This suggests that N. obtusa may be acting synergistically with existing stressors on Lake Scugog to exacerbate challenges with benthic hypoxia.

Glyphosate low doses reduce waterlogging damage in lettuce plants subjected to waterlogging and contribute to hormesis

ABSTRACT Drift from herbicides in fields adjacent to non-target crops, together with waterlogging can be detrimental to lettuce (Lactuca sativa L.). The objective of the study was to determine physiological responses of lettuce plants to exposure to glyphosate and waterlogging. Lettuce plants were subjected to treatments of combinations of foliar applications of glyphosate (45 g a.e.·ha−1) and waterlogging, and a treatment with drainage condition. Herbicide in conjunction with waterlogging, and waterlogging alone, reduced accumulation of total dry matter and leaves, as was net photosynthesis related to stomatal closure, photosystem II damage, and loss of membrane stability. Application of low doses of glyphosate on waterlogged plants favored accumulation of dry mass in the root that may be related to increase in carbohydrates to produce energy under low oxygen availability, these results indicate possible hormesis in lettuce plants to glyphosate and could be useful to reduce waterlogging damage in lettuce plants.

MODL-26. A PROTOCOL TO ADAPT GLIOBLASTOMA IN VITRO CULTURE SYSTEMS INTO ORGANOID MODELS USING NEUROCULT™ NS-A PROLIFERATION MEDIUM

Abstract Glioblastoma (GBM) is a malignant and aggressive brain tumor that is difficult to treat due to its heterogeneity. Traditional in vitro models (i.e. monolayers and tumorspheres) do not recapitulate this heterogeneity, leading to difficulty assessing new therapeutic strategies. Culturing GBM cells as organoids may provide a better method to retain the phenotype of the parent tumor. Here, we present a protocol for generating GBM organoids using NeuroCult™ NS-A Proliferation Medium, a medium commonly used for tumorsphere cultures. Two methods were assessed for the initial stage of formation, each suitable depending on throughput and cell source. In the first method, tumorspheres were dissociated and single cells were mixed with Growth Factor Reduced Matrigel® at a 1:4 ratio to form 15 μL droplets with 1000 cells per droplet. In the second method, 9000 cells from dissociated tumorspheres were seeded per well in a 96-well U-bottom plate and cultured for 5 days to form aggregates. On day 6, the aggregates were embedded in 15 μL Matrigel® droplets. In both methods, polymerized droplets were then cultured in suspension in stationary 6-well plates for 3 days, then maintained on an orbital shaker with full-medium changes every 2 - 3 days. Organoids were cryosectioned and processed for immunofluorescence at 5 - 6 weeks. In vivo, GBM tumors display an architecture containing regions of high and low nutrient and oxygen availability around a necrotic core. GBM organoids generated using this protocol exhibited distinct areas of proliferation near the organoid rim (Ki67+) and hypoxia (CA9+) near the core, mimicking this in vivo architecture (n = 3 GBM cell lines). Organoids grew to 2 - 4 mm in diameter and expressed glioma markers including TUJ1, Nestin, SOX2, OLIG2, and GFAP. These data show that NeuroCult™ NS-A Proliferation Medium can be used to adapt traditional GBM culture systems into organoids.

Sulfur-cycling chemolithoautotrophic microbial community dominates a cold, anoxic, hypersaline Arctic spring

BackgroundGypsum Hill Spring, located in Nunavut in the Canadian High Arctic, is a rare example of a cold saline spring arising through thick permafrost. It perennially discharges cold (~ 7 °C), hypersaline (7–8% salinity), anoxic (~ 0.04 ppm O2), and highly reducing (~ − 430 mV) brines rich in sulfate (2.2 g.L−1) and sulfide (9.5 ppm), making Gypsum Hill an analog to putative sulfate-rich briny habitats on extraterrestrial bodies such as Mars.ResultsGenome-resolved metagenomics and metatranscriptomics were utilized to describe an active microbial community containing novel metagenome-assembled genomes and dominated by sulfur-cycling Desulfobacterota and Gammaproteobacteria. Sulfate reduction was dominated by hydrogen-oxidizing chemolithoautotrophic Desulfovibrionaceae sp. and was identified in phyla not typically associated with sulfate reduction in novel lineages of Spirochaetota and Bacteroidota. Highly abundant and active sulfur-reducing Desulfuromusa sp. highly transcribed non-coding RNAs associated with transcriptional regulation, showing potential evidence of putative metabolic flexibility in response to substrate availability. Despite low oxygen availability, sulfide oxidation was primarily attributed to aerobic chemolithoautotrophic Halothiobacillaceae. Low abundance and transcription of photoautotrophs indicated sulfur-based chemolithoautotrophy drives primary productivity even during periods of constant illumination.ConclusionsWe identified a rare surficial chemolithoautotrophic, sulfur-cycling microbial community active in a unique anoxic, cold, hypersaline Arctic spring. We detected Mars-relevant metabolisms including hydrogenotrophic sulfate reduction, sulfur reduction, and sulfide oxidation, which indicate the potential for microbial life in analogous S-rich brines on past and present Mars.CDmZk6dAQUX4zKwy7_vWAsVideo

An In-Depth Stability Study of the Essential Oils from Mentha × piperita, Mentha spicata, Origanum vulgare, and Thymus vulgaris: The Impact of Thermal and Storage Conditions

In recent years, there has been a growing scientific interest in essential oils due to their therapeutic and aromatic properties and as potential alternative natural additives for use as preservatives or antibiotics. However, the literature lacks a comprehensive understanding of their stability and how their composition and properties change over time under various conditions. Through this paper, we aim to enhance the existing literature by providing deeper insights into the stability of essential oils and the sustainability of chemical composition in a time-based approach under various conditions. Therefore, four essential oils of the Lamiaceae family (Origanum vulgare, Thymus vulgaris, Mentha spicata, and M. x piperita) were evaluated with respect to their chemical variation influenced by several factors, such as thermal and storage conditions. Three types of containers were utilized to store the essential oils, i.e., glass ampoules, glass tubes, and metallic containers with plastic caps, for up to six months in −20 °C, 4 °C, 23 °C (with or without light exposure), 35 °C, and 45 °C. Samples were routinely analyzed by GC-MS and components were subjected to principal component analysis to ascertain whether the identified constituents may be useful in reflecting the stability of the analyzed samples. The main compounds appeared to be more stable, while the degradation of minor constituents (<1.0%) occurred in all four essential oils despite the storage conditions. Overall, apart from a slight variation in the chemical load, essential oils can be considered stable for various applications, especially those stored under low oxygen availability conditions.

Sporulation conditions influence the surface and adhesion properties of Bacillus subtilis spores.

Spore-forming bacteria of the Bacillus subtilis group are responsible for recurrent contamination of processing lines in the food industry which can lead to food spoilage. The persistence of B. subtilis would be due to the high resistance of spores to extreme environmental condition and their propensity to contaminate surfaces. While it is well known that sporulation conditions modulate spore resistance properties, little is known about their effect on surface and adhesion properties. Here, we studied the impact of 13 sporulation conditions on the surface and adhesion properties of B. subtilis 168 spores. We showed that Ca2+ or Mg2+ depletion, lower oxygen availability, acidic pH as well as oxidative stresses during sporulation lead to the release of more hydrophobic and adherent spores. The consequences of these sporulation conditions on crust composition in carbohydrates and proteins were also evaluated. The crust glycans of spores produced in a sporulation medium depleted in Ca2+ or Mg2+ or oxygen-limited conditions were impaired and contained lower amounts of rhamnose and legionaminic acid. In addition, we showed that lower oxygen availability or addition of hydrogen peroxide during sporulation decreases the relative amount of two crust proteins (CgeA and CotY) and the changes observed in these conditions could be due to transcriptional repression of genes involved in crust synthesis in late stationary phase. The fact that sporulation conditions affect the ease with which spores can contaminate surfaces could explain the frequent and recurrent presence of B. subtilis spores in food processing lines.

Induction and Characterisation of Lignocellulolytic Activities from Novel Deep-Sea Fungal Secretomes

Fungi are increasingly recognised as being able to inhabit extreme environments. The deep sea is considered an extreme environment because of its low temperatures, high hydrostatic and lithostatic pressures, 3.5% salinity, and low oxygen, nutrient and light availability. Fungi inhabiting the deep sea may have evolved to produce proteins that allow them to survive these conditions. Investigation and characterisation of fungal lignocellulolytic enzymes from extreme environments like the deep sea is needed, as they may have unusual adaptations that would be useful in industry. This work, therefore, aimed to profile in detail the lignocellulolytic capabilities of fungi isolated from deep-sea sediments in the Atlantic Ocean, and a comparative lignocellulolytic terrestrial isolate. The isolates were strains of Emericellopsis maritima, Penicillium chrysogenum, P. antarcticum and Talaromyces stollii. Lignocellulolytic enzyme induction was achieved using liquid-state fermentation (LSF) with wheat bran as the main carbon source, while enzyme characteristics were evaluated using biochemical assays and gel-based proteomics. This study revealed that the isolates were halotolerant, produced xylanase over wide pH and temperature ranges, and produced a variety of glycoside hydrolase and feruloyl esterase activities. The T. stollii secretome demonstrated remarkable levels of exo-glycoside hydrolase activity, with xylanase activity optimum between pH 1.5–6.0 and temperatures between 1–60 °C, making this isolate an ideal candidate for biotechnological applications. This study is the first to quantitatively characterise xylanase activities and exo-glycoside hydrolase activities secreted by E. maritima, P. antarcticum and a marine T. stollii strain. This study is also the first to quantitatively characterise xylanase activities by a marine strain of P. chrysogenum during LSF.