Ubiquitous plastic pollution is a threat to the organisms’ survival and ecosystem functions, especially in aquatic environments. Although there is increasing concern about the toxicity of ...microplastics, knowledge about the effects of microplastics of diverse sizes and adverse impacts on freshwater organisms is still limited. In the present study, the alteration in life-history traits, antioxidant defense and energy metabolism of the model freshwater zooplankton Daphnia pulex were assessed after chronic exposure to gradient concentrations (0.5, 1, 2 and 4 mg/L) of 500-nm polystyrene microplastics (PS-MPs). Changes in protein abundance were analyzed using proteomics after exposure to 1 mg/L of PS-MPs for 14 days. The results showed that ingested PS-MPs accumulated in the digestive tract of D. pulex. 2 and 4 mg/L of PS-MPs inhibited the survival function and 4 mg/L of PS-MPs reduced the body length of D. pulex after 14 or 21 days of exposure. The exposure did not decrease the fecundity of D. pulex. After 14 days of exposure, PS-MPs changed the antioxidant capacity in a dose-dependent way and all concentrations of PS-MPs induced lipid oxidative damage. Exposure to 500-nm PS-MPs for 14 days decreased glucose and fructose contents and disturbed the lipid transport and utilization in D. pulex. Meanwhile, PS-MPs activated DNA repair and transcription regulation but inhibited lipid metabolism and response to unfolded or misfolded proteins. These results indicated that chronic exposure to 500-nm PS-MPs negatively affected D. pulex and showed similar toxic mechanisms to smaller nano-sized microplastics. Exposure to 500-nm PS-MPs resulted in restricted resources such as inhibited antioxidant capacity or energy metabolisms and D. pulex showed a potential trade-off among life-history traits to maintain fecundity at the cost of self-maintenance. The present study offers perspectives for understanding the differences in ecological effects caused by microplastics of different sizes.
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•500-nm polystyrene microplastics negatively affected D. pulex on multiple levels.•500-nm PS-MPs affected survival and body length but not fecundity of D. pulex.•Impacts on antioxidant defense and metabolic disorders were observed in D. pulex.•Chronic exposure to 500-nm PS-MPs changed abundance of key proteins in D. pulex.•There was a potential trade-off among life-history traits in D. pulex during exposure.
Glycogen is the major glucose reserve in eukaryotes, and defects in glycogen metabolism and structure lead to disease. Glycogenesis involves interaction of glycogenin (GN) with glycogen synthase ...(GS), where GS is activated by glucose-6-phosphate (G6P) and inactivated by phosphorylation. We describe the 2.6 Å resolution cryo-EM structure of phosphorylated human GS revealing an autoinhibited GS tetramer flanked by two GN dimers. Phosphorylated N- and C-termini from two GS protomers converge near the G6P-binding pocket and buttress against GS regulatory helices. This keeps GS in an inactive conformation mediated by phospho-Ser641 interactions with a composite "arginine cradle". Structure-guided mutagenesis perturbing interactions with phosphorylated tails led to increased basal/unstimulated GS activity. We propose that multivalent phosphorylation supports GS autoinhibition through interactions from a dynamic "spike" region, allowing a tuneable rheostat for regulating GS activity. This work therefore provides insights into glycogen synthesis regulation and facilitates studies of glycogen-related diseases.
The nutritional condition of juvenile mussels appears to play a major role in their performance after they are seeded into coastal mussel farms. However, the extent to which the nutritional condition ...of juvenile mussels varies with size and starvation are poorly understood. Therefore, this study measured the biochemical composition of juvenile green-lipped mussels of five sizes (range of 0.5–7.5 mm shell length), from three different sources (i.e., harvested from wild, hatchery, coastal floating upweller nursery system) and when subjected to starvation for up to two weeks. The biochemical composition of spat sampled on their arrival from all sources was dominated by protein (ranging from 24 to 70% dry tissue mass), followed by lipid (0.3–9.3%) and carbohydrate (0.3–2.8%). Subsequent starvation treatments predominantly affected carbohydrate content. Initially, spat of 1.1–1.4 mm (harvested wild spat) had the lowest initial carbohydrate content 73% lower than spat of 0.5–1.0 mm (hatchery spat) and 53–65% lower than spat of 1.5–2.0, 2.1–3.4 and 3.5–7.5 mm (hatchery spat that were reared to larger sizes in a floating upweller system). Following one and two weeks of starvation, carbohydrate energy reserves of spat from all size classes showed a decrease of 15–42% from their initial level, except spat of 1.1–1.4 mm (wild) which did not decrease with starvation. Fatty acid dietary markers sampled from both spat of 0.5–1.0 mm (hatchery) and spat of 1.1–1.4 mm (wild) prior to starvation indicated that diatoms were important contributors to the diet of spat from both sources. Following two weeks of starvation, spat from both groups utilised SFA 14:0 and PUFAs, including essential fatty acids EPA, as energy sources, but they conserved AA and DHA. The findings of this study suggest that carbohydrate is the main energy reserve utilised by green-lipped mussel spat when food supplies are limited. Therefore, improving the carbohydrate reserves of spat through appropriate nursery feeding regimes has the potential to improve their resilience to poor feeding conditions following seeding onto coastal mussel farms.
•Proximate composition of juvenile mussels 0.5–7.5 mm were dominated by protein.•Juvenile mussels primarily utilize carbohydrate reserve when starved for two weeks.•Juvenile mussels sourced from wild were in poor nutritional condition.•Fatty acids from diatoms are important in both wild and hatchery juvenile mussels.•Nursery culture of juvenile mussels should target improving carbohydrate reserves.
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•Chironomus riparius larvae ingested PE-MPs from contaminated sediment.•Highest accumulation of PE-MPs in larvae guts was within the size range of 32-63 μm.•Depletion of lipid content ...was observed in larvae exposed to PE-MPs.•Ingested PE-MPs induced oxidative damage and reduced the aerobic energy production.
Riverine sediments are major sinks of microplastics from inland anthropogenic activities, imposing a threat to freshwater benthic invertebrates. This study investigated the ingestion of three size-classes (SC) of irregularly shaped polyethylene microplastics (PE-MPs; SC I: 32−63 μm; II: 63−250 μm; III: 125−500 μm) after 48 h by dipteran larvae (detritivore/collector) Chironomus riparius, and the consequent effects on neurotransmission, energy allocation and oxidative stress. The tested PE-MPs concentrations (1.25; 5; 20 g kg−1) were within the range of concentrations reported in riverbanks from highly urbanised areas (1 - 9 g kg−1), except for 20 g kg−1 representing the worst-case scenario. After exposure to SC I, larvae presented high amounts (up to ∼2400 particles/organism) of PE-MPs in their guts, with an average size-range of 30−60 μm. In the SC II and III, larvae presented PE-MPs of higher diameter (up to 125 μm) and a visible gut obstruction. The high number of particles in the larval gut (SC I) and/or difficulties for their egestion (SC I, II and III) induced oxidative damage and reduced aerobic energy production. In addition, larvae exposed to SC II and III revealed depletion in their total lipid reserves as a consequence of lacking nutrients, and the ones exposed to SC III presented a decrease in their detoxification capacity.
These results highlight that freshwater detritivores with low selective feeding behaviour (e.g., chironomids) are more prone to ingest microplastics, with potentially adverse effects on cellular metabolism, redox status and antioxidant-detoxification defences. These harmful effects at lower levels of the biological organisation may ultimately affect organisms’ physiology and fitness.
Depletion of fossil fuel sources and their emissions have triggered a vigorous research in finding alternative and renewable energy sources. In this regard, algae are being exploited as a third ...generation feedstock for the production of biofuels such as bioethanol, biodiesel, biogas, and biohydrogen. However, algal based biofuel does not reach successful peak due to the higher cost issues in cultivation, harvesting and extraction steps. Therefore, this review presents an extensive detail of deriving biofuels from algal biomass starting from various algae cultivation systems like raceway pond and photobioreactors and its bottlenecks. Evolution of biofuel feedstocks from edible oils to algae have been addressed in the initial section of the manuscript to provide insights on the different generation of biofuel. Different configuration of photobioreactor systems used to reduce contamination risk and improve biomass productivity were extensively discussed. Photobioreactor performance greatly relies on the conditions under which it is operated. Hence, the importance of such conditions alike temperature, light intensity, inoculum size, CO2, nutrient concentration, and mixing in bioreactor performance have been described. As the lipid is the main component in biodiesel production, several pretreatment methods such as physical, chemical and biological for disrupting cell membrane to extract lipid were comprehensively reviewed and presented. This review article had put forth the recent advancement in the pretreatment methods like hydrothermal processing of algal biomasses using acid or alkali. Eventually, challenges and future dimensions in algal cultivation and pretreatment process were discussed in detail for making an economically viable algal biofuel.
•Energy demand and the importance of bioenergy as alternative fuel was addressed.•Classification of biofuels and significance of microalgae was discussed.•Bioethanol, biodiesel, biogas, biohydrogen from algae was extensively described.•Open pond and photo bioreactor based cultivation and its development was reviewed.•Pretreatment processes, factors affecting algal fuel production was presented.
Microplastics are a widespread environmental contaminant. Although detrimental effects on aquatic organisms are well documented, little is known about the long-term effects of microplastic exposure ...to filter-feeding organisms at ecologically realistic levels. This study investigates the effects of environmentally relevant concentrations of polyethylene micro beads ranging in size from 3 to 30 μm, on the physiology and energetics of a coastal filter-feeding crab Petrolisthes laevigatus. We evaluated the impact of microplastics by exposing P. laevigatus to two different concentrations and exposure times: i) a chronic exposure for five months at 250 particles L−1, and ii) an acute exposure for 48 h at 20,800 particles L−1, ~80 times higher than the chronic exposure. The results showed that only chronic exposures elicited negative effects on the coastal crab in both, metabolic and physiological parameters. Our findings demonstrate a strong correlation between the ingestion rate and weight loss, even at low concentrations, the crabs exhibited severe nutritional damage as a result of long-term microplastic exposure. By contrast, acute exposure revealed no significant effects to the crabs, a possible explanation for this being short-term compensatory responses. These results suggest that environmentally relevant concentrations of microplastics are harmful to marine organisms, and they should be evaluated during realistic temporal scales, as their effects strongly dependent on the exposure time. Our results also suggest that the effects of microplastics have been likely underestimated to date, due to the dominance of short-term exposures (acute) reported in the current literature.
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•Petrolisthes laevigatus was not sensitive to acute exposures to polyethylene MP.•Chronic exposures to low MP concentrations decreased crab's energy budget.•Acute exposures to high MP concentrations likely underestimate MP effects.•Long term MP effects are due poor nutritional status.
Most microplastics are expected to sink and end up in marine sediments. However, very little is known concerning their potential impact on sediment-dwelling organisms. We studied the long-term impact ...of microplastic exposure on two sediment-dwelling bivalve species. Ennucula tenuis and Abra nitida were exposed to polyethylene microparticles at three concentrations (1; 10 and 25 mg/kg of sediment) for four weeks. Three size classes (4–6; 20–25 and 125–500 μm) were used to study the influence of size on microplastic ecotoxicity. Microplastic exposure did not affect survival, condition index or burrowing behaviour in either bivalve species. However, significant changes in energy reserves were observed. No changes were observed in protein, carbohydrate or lipid contents in E. tenuis, with the exception of a decrease in lipid content for one condition. However, total energy decreased in a dose-dependent manner for bivalves exposed to the largest particles. To the contrary, no significant changes in total energy were observed for A. nitida, although a significant decrease of protein content was observed for individuals exposed to the largest particles, at all concentrations. Concentration and particle size significantly influenced microplastic impacts on bivalves, the largest particles and higher concentrations leading to more severe effects. Several hypotheses are presented to explain the observed modulation of energy reserves, including the influence of microplastic size and concentration. Our results suggest that long-term exposure to microplastics at environmentally relevant concentrations can impact marine benthic biota.
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•Benthic bivalves were exposed to PE microparticles.•No effects were observed on mortality, general condition or burrowing.•Significant decreases in energy reserves occurred at environmental concentrations.•Particle size and concentration can influence microplastic ecotoxicity.
This study shows that exposure at environmentally relevant concentrations of microplastics can lead to deleterious effect on sediment-dwelling organisms, a group at high risk of exposure.
Fish cultivation in rice fields is a valuable resource in some rural areas of the world. Fish is a source of protein and an additional source of income for local farmers. However, the use of ...pesticides may impact fish and consumer health. The aim of this study was to evaluate exposure and effect biomarkers in native fish inhabiting a rice field during a production cycle. Samples of fish, water and sediment from a rice field in Santa Fe, Argentina were collected during a cultivation season (at the beginning: November 2017, in the middle: December 2017 and at the end: February 2018). At each sampling period, fish biomarkers of effect (biometric indices, hematological parameters, energy reserves, oxidative stress and neurotoxicity) were assessed together with pesticide screening in water, sediment, and fish samples. Only herbicides were present in water and sediment samples in agreement with land treatment before rice sowing stage, where only herbicides were applied. In general, the greatest water concentrations of bentazone, glyphosate and aminomethylphosphonic acid (AMPA), and the lowest sediment glyphosate and AMPA levels were observed at the beginning of the farming cycle. Fish bioaccumulated AMPA residues at all sampling periods and showed biological responses to cope with a stressful environment. Alterations in hematological parameters, mobilization of energetic reserves and activation of the antioxidant system were detected. However, no oxidative damage nor neurotoxic effects were present along the production cycle. Under a real exposure scenario, the present work demonstrates that biological changes are induced in fish to cope with stressors present in a rice field. Fish-rice coculture is an efficient and ecologically sustainable approach to increase food supplies, and a better understanding of the effect of this particular environment on fish would allow a greater and safer development of this promising productive activity in South American rice producing countries.
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•Exposure and effect biomarkers were assessed in fish inhabiting a rice field.•Fish bioaccumulated AMPA residues throughout the production period.•The liver showed the main biological responses as the crop cycle progressed.•Changes in hematology, energy reserves and antioxidant defenses were observed.•Real exposure scenarios allow a better understanding of herbicides effects on fish.
Fish accumulated AMPA and showed changes in hematological, energetic reserves and antioxidant defense biomarkers to cope with herbicide presence in a paddy field.
Macrophage polarization is accompanied by drastic changes in L-arginine metabolism. Two L-arginine catalytic enzymes, iNOS and arginase 1, are well-characterized hallmark molecules of classically and ...alternatively activated macrophages, respectively. The third metabolic fate of L-arginine is the generation of creatine that acts as a key source of cellular energy reserve, yet little is known about the role of creatine in the immune system. Here, genetic, genomic, metabolic, and immunological analyses revealed that creatine reprogrammed macrophage polarization by suppressing M(interferon-γ IFN-γ) yet promoting M(interleukin-4 IL-4) effector functions. Mechanistically, creatine inhibited the induction of immune effector molecules, including iNOS, by suppressing IFN-γ-JAK-STAT1 transcription-factor signaling while supporting IL-4-STAT6-activated arginase 1 expression by promoting chromatin remodeling. Depletion of intracellular creatine by ablation of the creatine transporter Slc6a8 altered macrophage-mediated immune responses in vivo. These results uncover a previously uncharacterized role for creatine in macrophage polarization by modulating cellular responses to cytokines such as IFN-γ and IL-4.
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•Macrophages maintain high intracellular creatine amounts via Slc6a8-mediated uptake•Creatine suppresses M(IFN-γ) polarization and attenuates antibacterial host defense•Creatine inhibits JAK-STAT1 signaling to downregulate IFN-γ effector gene expression•Creatine promotes expression of arginase 1 and supports M(IL-4) polarization
Creatine is an L-arginine downstream metabolite that is best known for its role as an energetic metabolism intermediate. Ji et al. show that through transporter Slc6a8-mediated uptake, macrophages accumulate high amounts of intracellular creatine that reprogram macrophage functionality by inhibiting M(IFN-γ) while promoting M(IL-4) polarization.
Copper oxide nanoparticles (CuO NP) have been produced on a large scale due to their economically interesting thermophysical properties. This heightens the concern about risks they may pose on their ...release into the environment, possibly affecting non-target organisms. Microalga are important organisms in ecotoxicological studies as they are at the base of the aquatic food chain, but information about their biochemical and photosynthetic changes in response CuO NP are still scarce. We studied the effects of CuO NP in Raphidocelis subcapitata using morphological, photosynthetic and biochemical biomarkers. Our results showed that the NP affected microalgal population growth with 0.70 mg Cu L−1 IC50–96 h (inhibition concentration). Based on predicted environmental concentrations of Cu NPs in aquatic environments, our results indicate potential risks of the NP to microalgae. Algal cell size, granularity and photosynthetic efficiencies were affected by the CuO NP at 0.97 and 11.74 mg Cu L−1. Furthermore, lipid metabolism was affected mostly at the highest NP concentration, but at environmentally relevant values (0.012 and 0.065 mg Cu L−1) the production of sterols (structural lipids) and triacylglycerols (reserve lipid) increased. Moreover, we found evidence of cell membrane impairment at the highest CuO NP concentration, and, as a photosynthetic response, the oxygen evolving complex was its main site of action. To the best of our knowledge, this is the first study to date to investigate microalgal lipid composition during CuO NP exposure, showing that it is a sensitive diagnostic tool. This research demonstrated that CuO NP may affect the physiology of R. subcapitata, and because they were observed in a primary producer, we foresee consequences to higher trophic levels in aquatic communities.
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•CuO NP led to increased cell size and granularity of R. subcapitata.•High CuO NP concentrations impaired the photosynthetic activity in R. subcapitata.•Energy reserve compounds increased in response to CuO NP.•Increase in structural lipids suggests cell membrane reinforcement.•Ionic copper and CuO NP toxicity share common features in microalgae response.
CuO NP damaged R. subcapitata cell division process impaired the photosynthetic activity and induced biochemical changes, particularly affecting lipid class composition.
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