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Malaria pathogenesis and parasite multiplication depend on the ability of Plasmodium merozoites to invade human erythrocytes. Invasion is a complex multi-step process involving multiple parasite proteins which can differ between species and has been most extensively studied in P. falciparum. However, dissecting the precise role of individual proteins has to date been limited by the availability of quantifiable phenotypic assays. In this study, we apply a new approach to assigning function to invasion proteins by using optical tweezers to directly manipulate recently egressed P. falciparum merozoites and erythrocytes and quantify the strength of attachment between them, as well as the frequency with which such attachments occur. Using a range of inhibitors, antibodies, and genetically modified strains including some generated specifically for this work, we quantitated the contribution of individual P. falciparum proteins to these merozoite-erythrocyte attachment interactions. Conditional deletion of the major P. falciparum merozoite surface protein PfMSP1, long thought to play a central role in initial attachment, had no impact on the force needed to pull merozoites and erythrocytes apart, whereas interventions that disrupted the function of several members of the EBA-175 like Antigen (PfEBA) family and Reticulocyte Binding Protein Homologue (PfRH) invasion ligand families did have a significant negative impact on attachment. Deletion of individual PfEBA and PfRH ligands reinforced the known redundancy within these families, with the deletion of some ligands impacting detachment force while others did not. By comparing over 4000 individual merozoite-erythrocyte interactions in a range of conditions and strains, we establish that the PfEBA/PfRH families play a central role in P. falciparum merozoite attachment, not the major merozoite surface protein PfMSP1., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Kals et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. For the purpose of open access, the author has applied a CC BY copyright license to any Author Accepted Manuscript Version arising from this submission.)

We report chemically fueled oscillations of vesicles. The population cycling of vesicles is driven by their self-reproduction and collapse within a biphasic reaction network involving the interplay of molecular and supramolecular events. We studied the oscillations on the molecular and supramolecular scales and tracked vesicle populations in time by interferometric scattering microscopy and dynamic light scattering. Complex supramolecular events were observed during oscillations─including vesicle reproduction, growth, and decomposition─and differences in the number, size, and mass of aggregates can often be observed within and between pulses. This system's dynamic behavior is reminiscent of a reproductive cycle in living cells.

Contaminants are increasingly accumulating in aquatic environments and biota, with potential adverse effects on individual organisms, communities and ecosystems. However, studies that explore the molecular changes in fish caused by environmentally relevant concentrations of metals, such as copper (Cu), are limited. This study uses embryos of the model organism zebrafish (Danio rerio) to investigate effect of Cu on the proteome and amino acid (AA) composition of fish. Wild-type embryos at 24 h post-fertilisation were exposed to Cu (2 µg L -1 to 120 µg L -1 ) for 96 h and the number of healthy larvae were determined based on larvae that had hatched and did not display loss of equilibrium (LOE). The effect concentrations where Cu caused a 10 % (EC 10 ) or 50 % (EC 50 ) decrease in the number of healthy larvae were calculated as 3.7 µg L -1 and 10.9 µg L -1 , respectively. Proteomics analysis of embryos exposed to the EC 10 and EC 50 concentrations of Cu revealed the proteome to differ more strongly after 48 h than 96 h, suggesting the acclimatisation of some larvae. Exposure to excess Cu caused differentially expressed proteins (DEPs) involved in oxidative stress, mitochondrial respiration, and neural transduction as well as the modulation of the AAs (Proline, Glycine and Alanine). This is the first study to suggest that LOE displayed by Cu-stressed fish may involve the disruption to GABAergic proteins and the calcium-dependent inhibitory neurotransmitter GABA. Moreover, this study highlights that proteomics and AA analysis can be used to identify potential biomarkers for environmental monitoring., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Introduction: The United States Centers for Disease Control and Prevention (CDC) advises testing individuals for COVID-19 after exposure or if they display symptoms. However, a deeper understanding of demographic factors associated with testing hesitancy is necessary., Methods: A US nationwide cross-sectional survey of adults with risk factors for developing severe COVID-19 ("high-risk" individuals) was conducted from August 18-September 5, 2023. Objectives included characterizing demographics and attitudes associated with COVID-19 testing. Inverse propensity weighting was used to weight the data to accurately reflect the high-risk adult US population as reflected in IQVIA medical claims data. We describe here the weighted results modeled to characterize demographic factors driving hesitancy., Results: In the weighted sample of 5019 respondents at high risk for severe COVID-19, 58.2% were female, 37.8% were ≥ 65 years old, 77.1% were White, and 13.9% had a postgraduate degree. Overall, 67% were Non-testers (who indicated that they were unlikely or unsure of their likelihood of being tested within the next 6 months); these respondents were significantly more likely than Testers (who indicated a higher probability of testing within 6 months) to be female (60.2 vs. 54.1%; odds ratio [OR] [95% confidence interval (CI)], 1.3 [1.1‒1.4]), aged ≥ 65 years old (41.5 vs. 30.3%; OR [95% CI] compared with ages 18‒34 years, 0.6 [0.5‒0.7]), White (82.1 vs. 66.8%; OR [95% CI], 1.4 [1.1‒1.8]), and to identify as politically conservative (40.9 vs. 18.1%; OR [95% CI], 2.6 [2.3‒2.9]). In contrast, Testers were significantly more likely than Non-testers to have previous experience with COVID-19 testing, infection, or vaccination; greater knowledge regarding COVID-19 and testing; greater healthcare engagement; and concerns about COVID-19., Conclusions: Older, female, White, rural-dwelling, and politically conservative high-risk adults are the most likely individuals to experience COVID-19 testing hesitancy. Understanding these demographic factors will help guide strategies to improve US testing rates., (© 2024. The Author(s).)

The gold rush at the end of the nineteenth century in south-eastern Australia resulted in the mobilization and re-deposition of vast quantities of tailings that modified the geomorphology of the associated river valleys. Previous studies of contamination risk in these systems have either been performed directly on mine wastes (e.g., battery sand) or at locations close to historical mine sites but have largely ignored the extensive area of riverine alluvial deposits extending downstream from gold mining locations. Here we studied the distribution of contaminant metal(loids) in the Loddon River catchment, one of the most intensively mined areas of the historical gold-rush period in Australia (1851-1914). Floodplain alluvium along the Loddon River was sampled to capture differences in metal and metalloid concentrations between the anthropogenic floodplain deposits and the underlying original floodplain. Elevated levels of arsenic up to 300 mg-As/kg were identified within the anthropogenic alluvial sediment, well above sediment guidelines (ISQG-high trigger value of 70 ppm) and substantially higher than in the pre-mining alluvium. Maximum arsenic concentrations were found at depth within the anthropogenic alluvium (plume-like), close to the contact with the original floodplain. The results obtained here indicate that arsenic may pose a significantly higher risk within this river catchment than previously assessed through analysis of surface floodplain soils. The risks of this submerged arsenic plume will require further investigation of its chemical form (speciation) to determine its mobility and potential bioavailability. Our work shows the long-lasting impact of historical gold mining on riverine landscapes., (© 2024. The Author(s).)

Trypanosomatid parasites undergo developmental regulation to adapt to the different environments encountered during their life cycle. In Trypanosoma brucei, a genome wide selectional screen previously identified a regulator of the protein family ESAG9, which is highly expressed in stumpy forms, a morphologically distinct bloodstream stage adapted for tsetse transmission. This regulator, TbREG9.1, has an orthologue in Trypanosoma congolense, despite the absence of a stumpy morphotype in that parasite species, which is an important cause of livestock trypanosomosis. RNAi mediated gene silencing of TcREG9.1 in Trypanosoma congolense caused a loss of attachment of the parasites to a surface substrate in vitro, a key feature of the biology of these parasites that is distinct from T. brucei. This detachment was phenocopied by treatment of the parasites with a phosphodiesterase inhibitor, which also promotes detachment in the insect trypanosomatid Crithidia fasciculata. RNAseq analysis revealed that TcREG9.1 silencing caused the upregulation of mRNAs for several classes of surface molecules, including transferrin receptor-like molecules, immunoreactive proteins in experimental bovine infections, and molecules related to those associated with stumpy development in T. brucei. Depletion of TcREG9.1 in vivo also generated an enhanced level of parasites in the blood circulation consistent with reduced parasite attachment to the microvasculature. The morphological progression to insect forms of the parasite was also perturbed. We propose a model whereby TcREG9.1 acts as a regulator of attachment and development, with detached parasites being adapted for transmission., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Silvester et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

River regulation by dams can alter flow regimes and organic matter dynamics, but less is known about how unregulated tributaries regulate organic matter composition and processing in the regulated river below the confluence. This study reports on water chemistry, especially dissolved organic matter (DOM) concentration and composition (dissolved organic carbon (DOC), organic nitrogen (DON), organic phosphorus (DOP) and combined amino acids (DCAA)) along the regulated Tumut and unregulated Goobarragandra (tributary) rivers under different flow conditions (base flow vs storm event) in south-east Australia. The tributary was significantly different from regulated and downstream sites during base flow conditions with higher temperature, pH, buffering capacity, DOC and nutrient concentrations (DON, DOP, DCAA). DOM characterisation by spectrometry and size exclusion chromatography revealed that the tributary contained a higher proportion of terrestrially derived humic-like and fulvic-like DOM. In contrast, regulated and downstream sites contained higher proportion of microbially derived DOM such as low molecular weight neutrals and protein-like components. Storm pulses of tributary flows into the regulated system, influenced both concentration and composition of DOM at the downstream site, which more strongly resembled the tributary site than the regulated site during the storm event. Additionally, we found that the tributary supplied fresh DOM, including small organic molecules to the regulated system during storm events. The presence of these different types of labile DOM can increase primary productivity and ecological functioning within regulated river reaches downstream of tributary junctions. This has important implications for the protection of unregulated tributary inflows within regulated river basins., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

In nutritional ecology the intake target is the diet that maximises consumer fitness. A key hypothesis of nutritional ecology is that natural selection has acted upon the behavioural and physiological traits of consumers to result in them Selectively Consuming prey to match the Intake Target (SCIT). SCIT has been documented in some herbivores and omnivores, which experience strong heterogeneity in the nutritional quality of available foods. Although carnivores experience a prey community with a much more homogeneous nutrient composition, SCIT by carnivores has nevertheless been deemed highly likely by some researchers. Here we test for SCIT for micronutrients (amino acids) in two freshwater carnivores: the river blackfish and the two-spined blackfish. Although both blackfishes exhibited non-random consumption of prey from the environment, this resulted in non-random consumption of amino acids in only one species, the river blackfish. Non-random consumption of amino acids by river blackfish was not SCIT, but instead an artefact of habitat-specific foraging. We present hypotheses to explain why wild populations of freshwater carnivores may not exhibit SCIT for amino acids. Our work highlights the need for careful, critical tests of the hypotheses and assumptions of nutritional ecology and its application to wild populations., (© 2023. The Author(s).)

Copper (Cu) is one of the most harmful contaminants in fresh-water systems. Fish larvae such as sacfry are particularly vulnerable to metals such as copper (Cu) due to a less-developed excretory organ system and permeable skin that can absorb metals directly from the water. However, the sublethal effects of metals on this life stage are not well understood. This study assessed the sublethal toxicity of Cu on purple-spotted gudgeon sacfry (PSG, Mogurnda adspersa). For this purpose, 96 h Cu toxicity bioassays were performed and toxic effects of Cu on PSG were measured at different levels of biological organization, from the individual (loss of equilibrium, wet weight), to tissue (chemical changes in retinal tissue composition) and molecular responses (whole body amino acid (AA) profiles). The EC 10 and EC 50 (ECx: effect concentration that affected X% of test organisms) were found to be 12 (9 - 15) µg Cu L -1 and 22 (19 - 24) µg Cu L -1 , respectively. Copper stress caused a decrease in total amino acid content and changed the AA profile of PSG compared to the controls. Proton-induced X-ray emission (PIXE) mapping techniques showed accumulation of Cu in the retinal tissues disturbing the distribution of other elements such as zinc, sulfur, phosphorus and potassium. Fourier-transform infrared (FTIR) microspectroscopy of control and Cu treated eye tissues revealed a change in protein secondary structure in retinal tissues in response to Cu accumulation, as well as decreased levels of the molecular retinal, consistent with the degradation of rhodopsin, a key protein in the visual sensory system. This is the first study to demonstrate the multi-level responses of PSG arising from exposure to environmentally realistic Cu concentrations and suggests that AA profiling can serve as a useful tool to assess the impacts of metals on fresh-water organisms., (Copyright © 2022. Published by Elsevier B.V.)

Contamination of freshwaters is increasing globally, with microalgae considered one of the most sensitive taxa to metal pollution. Here, we used 72 h bioassays to explore the biochemical effects of copper (Cu) on the amino acid (AA) profile and proteome of Chlorella sp. and advance our understanding of the molecular changes that occur in algal cells during exposure to environmentally realistic Cu concentrations. The Cu concentrations required to inhibit algal growth rate by 10% (EC 10 ) and 50% (EC 50 ) were 1.0 (0.7-1.2) µg L -1 and 2.0 (1.9-2.4) µg L -1 , respectively. The AA profile of Chlorella sp. showed increases in glycine and decreases in isoleucine, leucine, valine, and arginine, with increasing Cu. Proteomic analysis revealed the modulation of several proteins involved in energy production pathways, including: photosynthesis, carbon fixation, glycolysis, and oxidative phosphorylation, which likely assists in meeting increased energy demands under Cu-stressed conditions. Copper exposure also caused up-regulation of cellular processes and signalling proteins, and the down-regulation of proteins related to ribosomal structure and protein translation. These changes in biomolecular pathways have direct effects on the AA profile and total protein content and provide an explanation for the observed changes in amino acid profile, cell growth and morphology. This study shows the complex mode of action of Cu on Chlorella under environmentally realistic Cu concentrations and highlights several potential biomarkers for future investigations., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Laboratory studies of pathogens aim to limit complexity in order to disentangle the important parameters contributing to an infection. However, pathogens rarely exist in isolation, and hosts may sustain co-infections with multiple disease agents. These interact with each other and with the host immune system dynamically, with disease outcomes affected by the composition of the community of infecting pathogens, their order of colonization, competition for niches and nutrients, and immune modulation. While pathogen-immune interactions have been detailed elsewhere, here we examine the use of ecological and experimental studies of trypanosome and malaria infections to discuss the interactions between pathogens in mammal hosts and arthropod vectors, including recently developed laboratory models for co-infection. The implications of pathogen co-infection for disease therapy are also discussed.

Acid mine drainage (AMD) is one of the major environmental problems impacting aquatic ecosystems globally. We studied changes in the community composition of macroinvertebrates and amino acid (AA) profiles of dominant taxa along an AMD contamination gradient within the Dee River, Queensland, Australia to understand how AMD can affect the biomolecular composition of macroinvertebrates. Taxa richness and community composition of macroinvertebrates changed widely along the AMD gradient with significantly lower taxa richness recorded at the polluted sites compared to upstream and downstream sites. The Dipteran families: Chironomidae and Ceratopogonidae, the Odonata family Gomphidae, and the Coleoptera family Dytiscidae were the only families found at all sampling sites and were used here for AA analysis. There were significant variations in the AA profiles among the studied taxa. The AA profile of each taxon also varied among upstream, polluted and downstream sites suggesting that contamination of a river system with acid mine drainage not only alters the overall macroinvertebrate community composition but also significantly influences the AA profile of organisms that are tolerant to AMD. This study highlights the potential of using AA profiling to study the response of aquatic organisms to contamination gradients such as those associated with AMD., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Electron cryotomography (cryoET), an electron cryomicroscopy (cryoEM) modality, has changed our understanding of biological function by revealing the native molecular details of membranes, viruses, and cells. However, identification of individual molecules within tomograms from cryoET is challenging because of sample crowding and low signal-to-noise ratios. Here, we present a tagging strategy for cryoET that precisely identifies individual protein complexes in tomograms without relying on metal clusters. Our method makes use of DNA origami to produce "molecular signposts" that target molecules of interest, here via fluorescent fusion proteins, providing a platform generally applicable to biological surfaces. We demonstrate the specificity of signpost origami tags (SPOTs) in vitro as well as their suitability for cryoET of membrane vesicles, enveloped viruses, and the exterior of intact mammalian cells., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

The motility of microalgae has been studied extensively, particularly in model microorganisms such as Chlamydomonas reinhardtii. For this and other microalgal species, diurnal cycles are well known to control the metabolism, growth, and cell division. Diurnal variations, however, have been largely neglected in quantitative studies of motility. Here, we demonstrate using tracking microscopy how the motility statistics of C. reinhardtii are modulated by diurnal cycles. With nine independently inoculated cultures synchronized to the light-dark cycle at the exponential growth phase, we repeatedly observed that the mean swimming speed is greater during the dark period of a diurnal cycle. From this measurement, using a hydrodynamic power balance, we infer the mean flagellar beat frequency and conjecture that its diurnal variation reflects modulation of intracellular ATP. Our measurements also quantify the diurnal variations of the orientational and gravitactic transport of C. reinhardtii. We use this to explore the population-level consequences of diurnal variations of motility statistics by evaluating a prediction for how the gravitactic steady state changes with time during a diurnal cycle. Finally, we discuss the consequences of diurnal variations of microalgal motility in soil and pelagic environments., (Copyright © 2020 Biophysical Society. Published by Elsevier Inc. All rights reserved.)