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Journal of Biosciences

Springer Science and Business Media LLC

Preprints posted in the last 30 days, ranked by how well they match Journal of Biosciences's content profile, based on 12 papers previously published here. The average preprint has a 0.01% match score for this journal, so anything above that is already an above-average fit.

1
HLA-B51 induces IFN-γproduction in human natural killer cells

Omata, Y.; Hayakawa, H.; Sato, K.

2026-05-06 immunology 10.64898/2026.05.02.722370 medRxiv
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Behcets disease (BD) is a systemic inflammatory disease. It is considered as an autoinflammatory disease triggered by innate immunity rather than adaptive immunity. Human leukocyte antigen-B51 (HLA-B51) is the strongest genetic factor associated with BD. This study investigated how HLA class 1 molecules interact with innate immune cells and induce cytokine secretion. For this purpose, 293T cells transfected with a plasmid encoding HLA-B51 were cultured with natural killer (NK) cells obtained from healthy human donors. Within 24 h, the concentrations of interleukin-4 (IL-4), IL-8, and interferon-{gamma} (IFN-{gamma}) in the medium increased, indicating that NK cells secreted cytokines without undergoing cellular expansion for cytolysis. NK cells stimulated by nonself HLA-B51 produced IFN-{gamma} levels comparable to those produced by NK cells stimulated by self HLA-B51. NK cells carrying HLA-B51 were accurately recognized by overexpressing HLA-B51 on 293T cells. Moreover, ample intracellular IFN-{gamma} levels were detected in NK cells after stimulation with phorbol 12-myristate-13-acetate (PMA) plus ionomycin. KLRK1 (CD314)-positive cells mainly primarily accounted for IFN-{gamma}-producing cells, whereas KLRK1-negative cells did not. In contrast, both NCR1 (CD335)-positive and -negative cells contributed to IFN-{gamma} production. We next investigated whether HLA-B51 on the surface of 293T cells stimulates KLRK1 as a ligand causing IFN-{gamma} secretion. In masking experiments using anti-KLRK1 antibodies, NK cells with high levels of cell surface KLRK1 decreased the production of IFN-{gamma}. Conversely, human NK cell line KHYG1 cells also produced IFN-{gamma} in culture with 293T cells, but did not increase IFN-{gamma} through HLA-B51 stimulation. The mRNA expression of the signal adaptor protein HCST (DAP10) in KHYG1 cells was lower than that in NK cells, whereas the relative expression of IL-2RA in KHYG1 cells was higher than that in NK cells. These findings suggest that HLA-B51 can interact with KLRK1 on the NK cells inducing IFN-{gamma} secretion, whereas IL-2 signals outweigh HLA-51 stimulation in KHYG1 cells.

2
The contribution of non-additive genetic effects to the genetic variance of polyploid species.

Clo, J.

2026-05-14 genetics 10.64898/2026.05.12.724556 medRxiv
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Whole genome duplication is a common mutation in eukaryotes with far-reaching phenotypic effects. The resulting morphological, physiological, and fitness consequences and how they affect the survival probability of newly polyploid lineages are intensively studied, but very little is known about the effect of genome doubling on the short-term evolvability of populations. Understanding the effect of polyploidization on the adaptive potential of populations is of crucial importance to predict the future of polyploid populations. In this paper, I investigate the immediate consequences of genome doubling on the genetic variance of populations. To do so, I performed numerical iterations and simulations of how the genetic variance of a quantitative trait changes after polyploidization, under different genetic architectures (additivity, dominance, and epistasis). I found that genetic variance generally decreases after genome doubling. Non-additive gene actions can make autotetraploid populations genetically more diverse than their diploid progenitors in rare cases, notably with overdominance and directional epistasis. By collecting estimates from the agronomic literature, I found that both dominance and epistatic variance contribute to the genetic variance of polyploid populations. These results bring new insights into the adaptive potential of newly formed tetraploid populations, and call for further experimental investigations of how polyploidization is associated with a short-term decrease in evolvability.

3
Global epistasis in ecosystems arises from resource constraints

Kuehn, S.

2026-05-15 ecology 10.64898/2026.05.12.724736 medRxiv
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Global epistasis refers to the observation that the effect of a mutation or modification depends on the state of a biological system, not its detailed composition. Such patterns have been reported across biological scales, from proteins to organisms and ecosystems. In its simplest form, global epistasis appears as a linear relationship between the change in function or fitness due to a perturbation, and the background level of function or fitness. The mechanistic basis of global epistasis, particularly in ecological systems, remains unresolved. Here, we propose that in microbial communities, global epistasis describing the impact of adding a species to a community on function arises generically from constraints imposed by shared resource pools. We illustrate this mechanism in a single-species system growing on multiple substitutable resources, where global epistasis follows directly from nutrient limitation by an essential non-substitutable resource. We then extend this framework to multi-species communities competing for a single resource and show that the marginal effect of adding a species depends linearly on background community function, with a slope determined by the fraction of the resource claimed by the added species. We show that global epistasis persists in trophic cascades, but that facilitation and niche partitioning qualitatively break the linear dependence. This study provides a simple explanation for the appearance of global epistasis in ecosystems, and suggests that global epistasis should be a null expectation in ecosystems governed by competition. Our results propose that coupling between perturbations and shared resource pools might also help explain global epistasis at the organismal level.

4
Counting to two: how phages decide between lysis and lysogeny

Harju, J.; Guessous, G.; Gitai, Z.; Wingreen, N. S.

2026-05-17 biophysics 10.64898/2026.05.14.725151 medRxiv
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Upon infecting a bacterium, temperate phages must decide between killing the cell to reproduce (lysis) or entering a symbiotic lifestyle (lysogeny). This choice is often informed by the cells state, as well as the number of infecting phage particles (MOI). Since phage gene copy numbers scale identically with MOI, an MOI-dependent decision requires a fast-acting asymmetry between the lytic and lysogenic pathways. We introduce a minimal model suggesting that only a handful of coupling mechanisms can produce such an asymmetry; for instance via a host protease, kinase, or RNase acting on one pathway. By distilling complex regulatory networks to their essential components, our model clarifies the logic of lysis-lysogeny decision mechanisms across phage species.

5
Decoupling glycation from mortality: glucose, but not methylglyoxal, reduces survival in zebra finches

Moreno Borrallo, A.; Jaramillo Ortiz, S.; Schaeffer-Reiss, C.; Zumsteg, J.; Villette, C.; Heintz, D.; Mata Betancourt, A.; Robin, J. P.; Allak, A. L.; Criscuolo, F.; Bertile, F.

2026-05-07 physiology 10.64898/2026.05.04.722681 medRxiv
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Birds provide a unique model for ageing research, as they exhibit higher mass-adjusted metabolic rates and blood glucose levels than other vertebrate groups, yet demonstrate greater longevity and slower senescence compared to mammals of similar body size. This challenges the "pace of life syndrome" hypothesis, which predicts that high metabolic rates and elevated glucose should correlate with shorter lifespans. While the effects of glucose, glycation, and advanced glycation end-products (AGEs) on ageing are well-documented in humans and the conventional models used in biomedical research, their impact on avian physiology and ageing remains poorly understood. Some evidence suggests that birds possess adaptations mitigating the potential detrimental effects of glucose levels, which are much higher than those of all other vertebrate groups. However, previous studies indicate that elevated glucose predicts reduced lifespan, and protein glycation--varying with age--can influence survival and some fitness-related traits. This implies that glycation or AGE accumulation may have relevant effects on avian longevity. In this study, we experimentally investigated how one year of dietary supplementation with glucose or methylglyoxal affects survival and ageing markers (metabolic rate, flying performance, and beak coloration) in captive zebra finches (Taeniopygia guttata). Our results reveal a significant increase in mortality exclusively in glucose-supplemented birds. Although glucose treatment elevated albumin glycation rate and AGE formation--the latter also observed with methylglyoxal supplementation--these variables did not directly explain the increased mortality in glucose-treated birds, which was absent in methylglyoxal-treated individuals despite similar AGE accumulation. Additionally, we observed some effects on the assessed senescence markers, with an age-related constraint on seasonal metabolic adjustment, and a treatment-influenced age decline in secondary sexual traits expression. These findings support the use of these markers as proxies for senescence in zebra finches. We also discuss alternative mechanisms, independent of the glycation cascade, which may contribute to mortality. A seasonal decline in flight performance, particularly during peak mortality periods, suggests a broader deterioration of health. Thus, although we demonstrate glucose supplementation to be more deleterious than methylglyoxal, the underlying mechanisms for the observed increase in mortality induced by the treatment remain unresolved.

6
Computational drug repurposing identified Artemisinin and Mebendazole as potential inhibitors of virulence-associated proteins SKSR and essential kinases CpCDPK1 of Cryptosporidium parvum

Parveen, ; Saini, D.; Kumar, M.; Kapinder, ; Singh, A.; Jamil Khan, N.; Manzoor, N.; Sharma, M.; Kumar, P.

2026-05-19 molecular biology 10.64898/2026.05.17.725751 medRxiv
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Cryptosporidium parvum is a protozoan parasite responsible for cryptosporidiosis, significantly threatening immunocompromised individuals, particularly HIV/AIDS patients, by causing severe diarrhea and potential mortality. Current treatments are largely ineffective, prompting investigations into new therapeutic options. This study evaluated two antiparasitic drugs: Mebendazole, used for helminth infections, and Artemisinin, used for malaria. The SKSR gene family encodes virulence factors in C. parvum, and Calcium-dependent protein kinase1 (CpCDPK1) regulates the life cycle of C. parvum; targeting these proteins may reduce growth and infection in hosts. In the current study, molecular docking was conducted taking Mebendazole and Artemisinin drugs as ligands, SKSR gene family and CpCDPK1 proteins as drug targets. Results with SKSR showed binding energy of -4.9 kcal/mol, -6.72 kcal/mol for Mebendazole and Artemisinin, respectively. Whereas, with CpCDPK1, the binding energies were -6.44 kcal/mol, -9.18 kcal/mol for Mebendazole and Artemisinin, respectively. Docking of Nitazoxanide (an in-use drug for C. parvum) with SKSR and CpCDPK1 revealed binding energies -4.2 kcal/mol, -4.81 kcal/mol, respectively. The stability of the proteins (targets) upon binding to the ligands was assessed by performing all-atom MD simulations for 100ns using the GROMACS package. No major variations were observed upon binding of Artemisinin and Mebendazole to SKSR and CpCDPK1. The findings of MD simulations imply that both proteins maintain their stability upon binding of Artemisinin and Mebendazole. Molecular Docking and MD simulation studies suggest that Artemisinin and Mebendazole are potential candidates for repurposing in the treatment of C. parvum infections, with recommendations for in vitro studies to validate these findings.

7
Temporal Structure of Environmental Noise Controls the Localization and Tracking of Populations of Chemotactic Microorganisms

Arencibia, G.; Gutierrez, M. E.; Panetsos, F.

2026-05-12 bioengineering 10.64898/2026.05.07.723364 medRxiv
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The ability of chemotactic populations to localize and track targets in fluctuating environments depends critically on the temporal structure of environmental signals. Using a minimal agent-based framework of non-interacting run-and-tumble cells implementing an E. coli-inspired temporal sensing strategy, populations are exposed to static and moving chemoattractant fields perturbed by noise with controlled temporal structure, spanning white, pink (1/f), and correlated Ornstein-Uhlenbeck processes. Chemotactic populations are found to act as temporal filters, robustly suppressing fast fluctuations while remaining highly sensitive to slowly varying perturbations. As a consequence, chemotactic performance is governed not by noise amplitude, but by its temporal correlations. By continuously varying the noise correlation time, a critical regime emerges at{tau} c [~]{tau} run, where aggregates lose stability, tracking errors increase sharply, and spatial dispersion rises. Power spectral analysis further shows that the low-frequency power fraction of the signal provides a strong predictor of failure, outperforming total signal variance and establishing a direct link between environmental noise spectra and collective behavior. Introducing external flow reveals that advective transport amplifies noise-induced destabilization when it overlaps the chemotactic capture region, defining a combined spatiotemporal constraint on robustness. Together, these results identify temporal correlations and spectral structure as fundamental control parameters for chemotactic organization and provide a quantitative framework for predicting and designing collective behavior in fluctuating environments.

8
Collective chemotactic localization emerges from interaction-driven phase transitions under temporally correlated noise

Arencibia, G.; Gutierrez, M. E.; Lahoz-Beltra, R.; Panetsos, F.

2026-05-13 bioengineering 10.64898/2026.05.10.724076 medRxiv
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Chemotactic microorganisms operate in environments where signals are not only noisy but temporally structured, with finite correlation times that can severely impair gradient sensing and target localization. While previous models have extensively characterized the effects of fluctuating environments on individual chemotaxis, most theoretical frameworks treat agents as non-interacting, leaving unresolved how inter-bacterial interactions reshape collective robustness under temporally correlated noise. Here, we introduce a two-dimensional agent-based model of interacting run-and-tumble bacteria navigating noisy chemotactic landscapes. We show that short-range isotropic cohesion induces a two-stage collective response: interactions first stabilize population connectivity and above a finite interaction threshold, this structural cohesion translates into robust target localization even in regimes where individual chemotaxis fails. The resulting transition reveals an intermediate phase of cohesive but weakly localized states, demonstrating that structural condensation and functional targeting are distinct collective observables. We further demonstrate that selective heterotypic interactions in binary populations produce a structurally distinct collective regime characterized by dynamically maintained red-blue contact networks composed of transient mixed dimers and local heterotypic motifs. Unlike isotropic cohesion, selective interactions reorganize local contact topology without generating macroscopic condensation. These structures are quantitatively characterized through bond density, mixing statistics, and anisotropy metrics, and are governed primarily by interaction specificity rather than by environmental noise persistence. Together, these results establish that collective chemotactic behavior is controlled by the interplay between temporal signal correlations and interaction topology. More broadly, in this work we identify collective localization and internal organization as partially independent emergent properties of interacting active matter under fluctuating environments.

9
Pathogenesis of Alcohol-Exacerbated Malaria in Plasmodium berghei-Infected Mice

Bertrand Yuwong, W.; Nadege Emegam, K.; Shinyuy Lahngong, M.; Tiku Nda, H.; Tita Jugha, V.; Ambe Ngwa, F.; Sotoing Taiwe, G.

2026-05-05 immunology 10.64898/2026.04.30.720083 medRxiv
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IntroductionMalaria is still a pressing global health challenge, especially in sub-Saharan Africa, where behavioral factors such as alcohol consumption may exacerbate its impact. The present study is aimed at investigating the pathogenesis of alcohol-exacerbated malaria in Plasmodium berghei-infected an animal model (mice). MethodsMale mice were separated into four treatment groups: control, alcohol control, P. berghei and P. berghei plus acute alcohol treatment groups. Animals were infected with malaria through intraperitoneal injection of P. berghei and an acute dose of ethanol (20% v/v) was introduced 48 hours post-infection. Parasitaemia was monitored using the Giemsa-stained thin blood smears. Haematological parameters were assessed using automated blood analyser. Liver function was evaluated by measuring serum levels of AST and ALT and cytokine profiles (TNF-, INF-{gamma}, IL-6, IL-1{beta}) were quantified using ELISA kits. ResultsResults show that acute alcohol intake led to a significant increase in parasitaemia in the P. berghei group (p<0.01). Haematological analysis revealed a significant (p<0.001) reduction in RBC count, haemoglobin levels, haematocrit percentage, platelet count and others in the P. berghei plus acute alcohol group. Liver enzyme assays revealed an elevated AST and ALT levels (p<0.001) in the P. berghei group. Cytokine analysis revealed a significant (p<0.01) upregulation of pro-inflammatory cytokines (TNF- INF-{gamma}, IL-1{beta} and IL-6), due to acute alcohol. These results suggest that alcohol exacerbates malaria pathogenesis by increasing parasitaemia, promoting immune dysregulation and liver injury, mediated by a shift toward a pro-inflammatory cytokine profile.

10
The phenotypic nonspecificity of cell-to-cell signalling in Drosophila melanogaster.

Percival-Smith, A.; Brabrook, C.

2026-05-21 genetics 10.64898/2026.05.19.726339 medRxiv
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An expectation of a hypothesis that proposes cell-to-cell signalling pathways are redundant due to the redundancy of pathway terminal transcription factors (TFs) was tested by screening 35 signalling ligands (SLs) for rescue of a decapentaplegic (dpp) hypomorphic wing growth phenotype. The screen identified three examples of partial rescue: Hedgehog (HH), Semphorin 1a (SEMA1A) and Wnt ortholog 2 (WNT2). HH overexpression with dppGAL4 may increase the expression of DPP activity from the hypomorphic dpp alleles. However, SEMA1A and WNT2 did not phenocopy ectopic expression of HH or DPP and neither SEMA1A nor WNT2 were required for wing growth suggesting substitution of DPP for partial restoration of wing growth. The WNT2 rescue was dependent on the Frizzled 4 (FZ4) WNT receptor excluding the possibility that WNT2 weakly binds the DPP receptor. Although examples of phenotypic nonspecificity of SL function were identified, this is an expectation, and not direct proof, of the hypothesis of TF redundancy. Screen Report SummaryAn expectation of a hypothesis proposing that cell-to-cell signalling pathways are redundant due to the redundancy of the pathway terminal transcription factors was tested by screening for replacement of one signalling ligand (DPP; SLa) with another SLb for wing growth. Three non-DPP SLs were identified in the screen of 35SLs: HH, SEMA1A and WNT2. Genetic analysis of Sema1a and Wnt2 suggests functional complementation of dpp for wing growth suggesting that SEMA1A and WNT2 partially replace DPP for wing growth. Therefore, an expectation of the hypothesis is met.

11
Network reciprocity reshaped by environmental knowledge and feedback

Basak, A.; Kleshnina, M.; Sengupta, S.

2026-05-19 animal behavior and cognition 10.64898/2026.05.15.725397 medRxiv
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Cooperative interactions often unfold in environments that are shaped by collective behavior, yet how knowledge about such changing environments feeds back into evolutionary dynamics remains poorly understood. While network reciprocity explains how spatial structure enables clusters of cooperators to emerge and grow under certain conditions, it typically ignores how individuals respond to environmental change. Here, we integrate stochastic environmental feedback with network reciprocity to examine how knowledge about environmental state shapes the evolution of cooperation in structured populations. We compare regimes in which individuals either condition their behavior on the current state or remain unaware of it. Under weak selection, we derive a simple condition showing that cooperation is favored when the benefit-to-cost ratio exceeds a modified classic reciprocity threshold accounting for the effect of environmental transitions and state knowledge. Environmental shifts can either promote or hinder cooperation depending on accessibility and fidelity of state knowledge. Counterintuitively, greater knowledge does not universally enhance cooperation: for certain transition rules, state awareness raises the critical threshold for cooperation, a phenomenon we term a "knowledge curse". Our results reveal that, in an ever-changing environment, cooperation in structured populations emerges from a subtle interplay between environmental feedback and information availability.

12
Energetically constrained turnover drives the emergence of aging

Yao, M.; Deguchi, S.

2026-05-21 biophysics 10.64898/2026.05.19.726278 medRxiv
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Aging is characterized by progressive functional decline, yet why such decline is observed broadly across living systems remains unclear. While molecular and cellular mechanisms describe how aging progresses, they do not explain why functional decline should arise as a natural consequence of living organization. Here, we show that aging naturally emerges from three general features of life: unavoidable damage, turnover-mediated maintenance, and the energetic constraint of turnover. We develop a hierarchical damage-turnover model in which component-level damage and energetically constrained turnover jointly determine whole-system performance. In the model, damage stochastically converts functional components into non-functional components, whereas turnover restores component performance at a rate coupled to whole-system performance. Analytical and Monte Carlo analyses reveal two regimes: a non-aging regime, in which performance remains finite, and an aging regime, in which performance progressively collapses toward zero. Performance-independent turnover always maintains a positive steady state, whereas performance-dependent turnover generates irreversible decline when reduced performance weakens maintenance capacity. Stochastic fluctuations further promote collapse near the transition boundary, even when deterministic analysis predicts a nonzero steady state. These results indicate that unavoidable damage and energetically constrained turnover are sufficient to generate aging-like decline, providing a minimal theoretical explanation for long-term irreversibility in biological systems.

13
Rare plants can make an important contribution to sustain local biodiversity through biological interactions

Garcia, M. B.; Miranda-Cebrian, H.; Verdu, M.; Martin, D.; Blasco-Zumeta, J.; Jarne, M.; Olesen, J.

2026-05-18 ecology 10.64898/2026.05.16.725624 medRxiv
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Plants, as structural elements of habitats, contribute greatly to the maintenance of local biodiversity through their biological interactions. In this study we explore whether their rarity, according to Rabinowitzs (1981) three criteria, is related to the richness and diversity of arthropods and other plants they are associated to, in a gypsum-rich steppe. We first analysed whether the geographic abundance and ecological specialisation of 32 characteristic and dominant plant species are related to the diversity (richness and phylogenetic diversity (MPD)) and degree of local specialisation of arthropods associated with them (1,694 taxa). Then, we focused on a non endemic and non specialized plant in the study area (Krascheninnikovia ceratoides) to explore the effect of population size on two types of interactions: aerial arthropods and plant facilitation. Results indicate that: 1) plant species abundance (geographical range) is not related to the richness or MPD of communities of associated arthropods, 2) plant species ecological specialization (edaphic endemisms or gypsophiles) do not contribute differentially to the maintenance of singular arthropod communities, and 3) the community of aerial arthropods and plants interacting with K. ceratoides in a small population are not necessarily less diverse than those in patches of similar size in a large population. Results also revealed that the two plant species with fewer interactions (one rare, one widespread) do show the highest singularity in their interactions with arthropods. Our study illustrates the important contribution of rare plants to the conservation of local biodiversity.

14
Stochastic colonization and host-to-host transmission shape gut bacterial variability

Lu, C. Y.; Tashev, S. A.; Pessoa, P.; Kruithoff, R.; Shepherd, D. P.; Presse, S.

2026-05-12 microbiology 10.64898/2026.05.11.724410 medRxiv
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Understanding the kinetic processes that govern bacterial population dynamics within hosts is critical in developing effective strategies to control microbiota. However, inferring population dynamics is challenging due to large host-to-host bacterial population variability stemming from stochastic colonization events, as well as the inability to continuously monitor the bacterial population without disturbing the host. Using C. elegans fed E. coli under different diets, we show that early colonization acts as a stochastic bottleneck that drives substantial divergence in host-level bacterial loads, and that the spreading of bacteria from colonized worms to sterile ones regulates this variability by altering effective colonization pressure. These conclusions are drawn using a simulation-based inference framework that quantifies stochastic within-host population dynamics from discrete snapshot data, enabling inference of effective colonization and growth rates across heterogeneous hosts with variable carrying capacities. Applying this framework, we further demonstrate that the bacterial predator B. bacteriovorus reduces average gut bacterial loads by two orders of magnitude, primarily by suppressing environmental recolonization and subsequent host-to-host transmission rather than eliminating established intra-host populations. Together, these results reveal that host-associated microbial population dynamics are strongly impacted by environmental colonization processes that modulate stochastic entry events.

15
Multilevel computational approach to unlock the potential inhibitors of biofilm-EPS, persistence and quinolone signalling in Pseudomonas aeruginosa using mangrove-derived bioactive phytochemicals

Behera, S.; Kungwani, N.; Mohanta, Y. K.

2026-05-09 microbiology 10.64898/2026.05.08.722855 medRxiv
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Pseudomonas aeruginosa, a Gram-negative opportunistic pathogen is well known for life-threatening acute infections among the human population. The bacterium can withstand most antibiotics by using their high levels of inherent and acquired resistance mechanisms such as Biofilm-EPS, Persistence, and Quorum sensing (QS). Owing to the importance of adaptive antibiotic multi-drug resistance of P. aeruginosa, the current investigation is aimed to explore the phytochemicals derived from mangrove plants as potential agents to control biofilm and drug resistance mechanisms through a multi-mechanistic computational approach. For identifying potential compounds and target, In-silico drug repurposing technique is implemented by docking/virtual screening of 49 phytochemical compounds against 18 proteins involved in the Persister Cell formation, QS, and EPS synthesis in P. aeruginosa which resulted the proteins RelA and SpoT (persistence), PqsA, and PqSR (QS), and PelA and PelB (EPS synthesis) and compounds Taraxerone and Taraxerol to be potential. The results of docking were well corroborated with MD simulations. These targets and compounds explored through in-silico approach, are found to target potential antimicrobial pathways involving EPS synthesis, persistence genes, and QS, aiming to enhance antibiotic efficacy. Further, this study could be reference for in-vivo and in-vitro investigations to evaluate the further effectiveness of the compounds and potentiality of the proteins for MDR therapeutics of P. aeruginosa.

16
Chloroplast movements in siphonous macroalgae in response to high light and grazing

Mattila, H.; Lopes, P.; Havurinne, V.; Goessling, J. W.; Cartaxana, P.; Cruz, S.

2026-05-15 cell biology 10.64898/2026.05.14.725087 medRxiv
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Fast cytoplasmic streaming enables extensive chloroplast movements in the giant cells of unicellular, siphonous macroalgae. Here, we studied chloroplast movements in two such algae: the Dasycladalean Acetabularia acetabulum and the Bryopsidales Bryopsis sp.. We hypothesised that chloroplast movements function as a protective avoidance mechanism under excess light, particularly in Bryopsis sp., which lacks capacity for fast induction of photoprotective non-photochemical quenching (NPQ) and state transitions. In addition, we also investigated whether chloroplast movements are involved in responses to wounding and herbivory. The movements were studied by light microscopy, photography and pulse modulated chlorophyll a fluorescence quenching analysis. Chemical inhibitors of actin polymerization and microtubules assembly were used to confirm that the observed effects were active responses controlled by the cytoskeleton. A. acetabulum responded to high light by reversible chloroplast aggregation, probed by macro-imaging; and chemical inhibition of chloroplast movements led to an enhancement of Photosystem II photoinhibition, as probed by the fluorescence parameter FV/FM. No chloroplast movements were observed in Bryopsis sp. in response to high light. In A. acetabulum, wounding caused either by cutting or due to feeding by the sap-sucking sea slug Elysia timida triggered aggregation of chloroplasts within minutes of incurring the damage. Interestingly, the aggregation also occurred in intact cells away from the cutting site. Furthermore, the addition of media collected from the vicinity of cut algae was sufficient to induce chloroplast aggregation in intact algae, suggesting that water-borne cues or signals triggered the aggregation response in A. acetabulum. Bryopsis sp., however, responded to cutting by only local chloroplast aggregation. The relevance of chloroplast movements in protection against both abiotic and biotic stressors in A. acetabulum, and the potential reasons behind the different defence strategies of the algae, are discussed.

17
A quantitative framework for bacterial competition during starvation

Schink, S. J.; Gerland, U. J.; Gough, Z. H.; Dauber, M.; Seyed-Allaei, H.; Biselli, E.; Brameyer, S.

2026-05-21 systems biology 10.64898/2026.05.19.726047 medRxiv
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Bacterial communities often spend long periods under starvation, where survival depends not only on their intrinsic ability to withstand stress but also on nutrients released by dying neighbors. This creates a distinct form of competition: cells compete for recycled necromass, and the outcome should depend on physiological traits that determine nutrient uptake and maintenance demand. Here, we develop a quantitative framework for this competition using Escherichia coli populations whose starvation physiology is tuned by prior growth history. Fast-grown populations have higher maintenance demands and die slightly faster in monoculture, whereas slow-grown populations are better adapted to starvation. In co-culture, these physiological differences are strongly amplified in a frequency-dependent manner: less-adapted populations die several-fold faster than in monoculture, whereas well-adapted populations can reduce their death rate below that of stationary-phase adapted monocultures. We explain these dynamics with a shared-energy-pool model in which death releases recyclable nutrients, surviving cells consume them for maintenance, and intracellular energy sets death rate. Using independently measured parameters, the model makes parameter-free predictions for competitive survival. The predicted instantaneous death rates collapse onto a universal function of the population ratio over four orders of magnitude. Our results establish necromass recycling as a quantitative basis for bacterial competition during starvation and lay the foundation for modeling communities during starvation.

18
Organelle scaling over a 100-fold cell size range

Wirshing, A. C. E.; Lew, D. J.

2026-05-13 cell biology 10.64898/2026.05.13.724986 medRxiv
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Cell size in a proliferating cell population generally varies over a limited range ([~]2-4-fold). Within such populations, organelle content increases with cell size maintaining a relatively constant organelle density (amount per cell volume). However, cells of different types can differ greatly in cell size as well as in organelle composition. In such cases, it is often unclear to what degree, if any, the differences in organelle composition are due to the difference in cell size. In principle, this issue could be resolved by examining situations where a proliferating population of cells of the same cell type exhibit much greater size variation. Here we characterize how organelle content scales with cell volume in the polymorphic fungus, A. pullulans, whose proliferating cells span a [~]100-fold size range. We find that mitochondria and ER content increases in proportion to cell volume, while this is not the case for vacuoles and peroxisomes. Thus, organelle composition is affected by cell size in this system.

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First occurrence of Corynespora cassiicola infecting chia plant in Bangladesh and its sensitivity to selected fungicides

Badhon, A. K.; Gupta, D. R.; Paul, S. K.; Ali, J.; Rahman, M. M.; Islam, T.

2026-05-06 molecular biology 10.64898/2026.05.01.722373 medRxiv
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Chia (Salvia hispanica L.) is an emerging crop in Bangladesh valued for its medicinal properties and economic significance. In March 2024, target spot-like symptoms were observed in an experimental chia field (24.75{degrees} N, 90.50{degrees} E) at Bangladesh Agricultural University in Mymensingh, Bangladesh with disease incidence ranging from 23% to 47% across approximately 0.25 ha. Initially appearing as brick-red spots, these symptoms developed into target-shaped concentric rings, affecting leaves, stems, and inflorescences. A total of 24 fungal isolates were recovered from infected tissue; two representative isolates (BGECh-3 and BGECh-4) were randomly selected for details characterization. Pathogen identity was established through morphological traits, multilocus phylogenetic analysis of internal transcribed spacer (ITS) and elongation factor 1-alpha (EF-1) genes sequence, and pathogenicity confirmation through Kochs postulates, collectively identifying the causal agent as Corynespora cassiicola. The isolates demonstrated a broad host range, successfully infecting brinjal, chili, bottle gourd, country bean, tomato, and soybean. In vitro fungicide sensitivity assays with seven commercial fungicides showed that both isolates were highly sensitive to Goldzim (50% carbendazim), which completely inhibited mycelial growth at 10 {micro}g mL-{superscript 1}. Conza (10% Hexaconazole) and Amister top (18.2% azoxystrobin + 11.4% difenoconazole) reduced growth by up to 85% and 67%, respectively at equal concentration. Other fungicides showed comparatively lower efficacy even at higher concentrations. This study represents the first report of target spot disease of chia caused by C. cassiicola in Bangladesh and provides insights for effective disease management strategies.

20
Comparison of Osteoblast Calcification in Bio-Oss, Cerasorb, Pro Osteon, and Bio-Tiss Cerabone

Ghasemi, A.; Farhad, S. Z.; Ostadsharif, M.

2026-05-17 bioengineering 10.64898/2026.05.12.724627 medRxiv
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BackgroundBone graft biomaterials play a critical role in bone regeneration by influencing osteoblast differentiation and mineralization. However, comparative data regarding the osteogenic potential of commonly used graft materials under standardized conditions remain limited. Method and materialIn this in vitro experimental study, osteoblast-like cells (MG-63) were cultured with four bone graft materials, including Bio-Oss, Cerasorb, Bio-Tiss Cerabone, and Pro Osteon. The relative mRNA expression of osteogenic markers (COL1 and OPN) was evaluated at 1, 7, 14, and 21 days using real-time PCR. Alkaline phosphatase (ALP) activity and mineralization capacity were also assessed using colorimetric assay and Alizarin Red staining. Data were analyzed using one-way ANOVA and Tukey post hoc test (P < 0.05). ResultsSignificant differences were observed among the tested materials across all evaluated parameters. Bio-Oss and Cerasorb demonstrated higher gene expression levels and ALP activity compared to Bio-Tiss Cerabone and Pro Osteon (P < 0.05). Mineralization analysis showed significantly greater calcium deposition in the Bio-Oss and Cerasorb groups, whereas Pro Osteon consistently exhibited the lowest osteogenic performance. ConclusionBone graft biomaterials significantly influence osteogenic activity in osteoblast-like cells. Bio-Oss and Cerasorb showed superior osteogenic potential, while Pro Osteon demonstrated weaker performance. These findings highlight the importance of material properties in optimizing bone regeneration.