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1.
Allyson K. Jackson Collin A. Eagles&#x;Smith W. Douglas Robinson 《Ecology and evolution》2021,11(11):7003
Cross‐ecosystem subsidies move substantial amounts of nutrients between ecosystems. Emergent aquatic insects are a particularly important prey source for riparian songbirds but may also move aquatic contaminants, such as mercury (Hg), to riparian food webs. While many studies focus on species that eat primarily emergent aquatic insects, we instead study riparian songbirds with flexible foraging strategies, exploiting both aquatic and terrestrial prey sources. The goal in this study is to trace reliance on aquatic prey sources and correlate it to Hg concentrations in common riparian arachnids (Families Tetragnathidae, Opiliones, and Salticidae) and songbirds (Common Yellowthroat Geothlypis trichas, Spotted Towhee Pipilo maculatus, Swainson''s Thrush Catharus ustulatus, Song Sparrow Melospiza melodia, and Yellow Warbler Setophaga petechia). We used stable isotopes of δ13C and δ15N and Bayesian mixing models in MixSIAR to determine the reliance of riparian predators on aquatic prey sources. Using mixed effects models, we found that arachnid families varied in their reliance on aquatic prey sources. While songbird species varied in their reliance on aquatic prey sources, songbirds sampled earlier in the season consistently relied more on aquatic prey sources than those sampled later in the season. For both arachnids and songbirds, we found a positive correlation between the amount of the aquatic prey source in their diet and their Hg concentrations. While the seasonal pulse of aquatic prey to terrestrial ecosystems is an important source of nutrients to riparian species, our results show that aquatic prey sources are linked with higher Hg exposure. For songbirds, reliance on aquatic prey sources early in the breeding season (and subsequent higher Hg exposure) coincides with timing of egg laying and development, both of which may be impacted by Hg exposure. 相似文献
2.
JEFF S. WESNER 《Freshwater Biology》2012,57(12):2465-2474
1. Empirical and theoretical research over the past decade has demonstrated the widespread importance of aquatic subsidies to terrestrial food webs. In particular, adult aquatic insects that emerge from streams and lakes are prey for terrestrial predators. While variation in the magnitude of this subsidy is clearly important, the potential top‐down effects of the predatory adults of some aquatic insects in terrestrial food webs are largely unknown. 2. I used published data on benthic insect density (as a proxy for emergence) in North and South America to explore how the proportion of benthic insects that are predatory as adults varies across a gradient of mean annual stream temperature. 3. The proportion of benthic insects that are predatory as adults varied widely across sites (0–12% by abundance; 0–86% by biomass). There was a positive relationship between mean annual stream temperature and the proportion of predatory adults across all sites, driven largely by the greater abundance/biomass of predatory taxa (e.g. odonates), relative to non‐predators (e.g. midges, mayflies, caddisflies), in tropical than in temperate streams. 4. The ‘trophic structure’ (i.e. the proportion of predators) of emerging adult aquatic insects is an understudied source of variation in aquatic–terrestrial interactions. Incorporation of trophic structure in future studies is needed to understand how future modification of fresh waters may affect adjacent terrestrial food webs through both bottom‐up and top‐down effects. 相似文献
3.
Linnea Norlin Pär Byström Jan Karlsson Martin Johansson Antonia Liess 《Freshwater Biology》2016,61(4):472-485
- With global warming, mean temperatures and brownification of many waterbodies are predicted to increase. This may have unknown consequences on aquatic consumer life histories and nutrient content, consumer‐mediated nutrient recycling, and nutrient transport between water and land.
- Using a large‐scale experimental pond facility, we altered temperature (ambient/+4 °C) and brownification (clear/humic) in a 2 × 2 factorial design (n = 16 pond sections) to test two aspects of climate change on Rana temporaria tadpole life‐history traits and on tadpole‐mediated nutrient pathways. On day 16 after hatching, we examined tadpole‐mediated nutrient recycling by measuring tadpole nutrient excretion and egestion rates and tadpole body nutrient content. We estimated tadpole growth and development rates from hatching to emergence and measured emergent frog body size and body nutrient content.
- Brownification increased total pond water nutrient availability and total pond water nitrogen (N) : phosphorous (P) ratios. Warming positively affected tadpole growth and development rates, whereas browning increased tadpole growth rate only under ambient temperatures. Emergent frog body P content decreased with warming, but only in the clear treatments. But despite these variations in body nutrient content, body stoichiometry remained within a relatively narrow stoichiometric range for both emergent frogs (P content: 1.4–1.8%, N content: 11.4–11.8% and carbon [C] content: 46.9–51.3%) and tadpoles (P content: 1.1–1.2%, N content: 10.1–11.7% and C content: 48.0–50.5%). Warming increased tadpole body P content and browning had a positive effect on tadpole body N content and tadpole N excretion rates, probably mediated by the increased pond water total N availability.
- We conclude that warming and brownification will interact in changing aquatic consumer growth and body nutrient stoichiometry. In addition, warming has the potential to affect emergent frog body nutrient content and may thus affect nutrient transport from water to land. Last, by increasing pond water N availability, brownification appears to intensify consumer P limitation and thus amplify consumer‐meditated N recycling.
4.
Carmella Vizza Beth L. Sanderson Holly J. Coe Dominic T. Chaloner 《Ecology and evolution》2017,7(5):1313-1324
Stable isotope ratios (δ13C and δ15N) have been used extensively to trace nutrients from Pacific salmon, but salmon transfer more than carbon and nitrogen to stream ecosystems, such as phosphorus, minerals, proteins, and lipids. To examine the importance of these nutrients, metrics other than isotopes need to be considered, particularly when so few studies have made direct links between these nutrients and how they affect riparian organisms. Our study specifically examined δ13C and δ15N of riparian organisms from salmon and non‐salmon streams in Idaho, USA, at different distances from the streams, and examined whether the quality of riparian plants and the body condition of invertebrates varied with access to these nutrients. Overall, quality and condition metrics did not mirror stable isotope patterns. Most notably, all riparian organisms exhibited elevated δ15N in salmon streams, but also with proximity to both stream types suggesting that both salmon and landscape factors may affect δ15N. The amount of nitrogen incorporated from Pacific salmon was low for all organisms (<20%) and did not correlate with measures of quality or condition, probably due to elevated δ15N at salmon streams reflecting historical salmon runs instead of current contributions. Salmon runs in these Idaho streams have been declining, and associated riparian ecosystems have probably seen about a 90% reduction in salmon‐derived nitrogen since the 1950s. In addition, our results support those of other studies that have cautioned that inferences from natural abundance isotope data, particularly in conjunction with mixing models for salmon‐derived nutrient percentage estimates, may be confounded by biogeochemical transformations of nitrogen, physiological processes, and even historical legacies of nitrogen sources. Critically, studies should move beyond simply describing isotopic patterns to focusing on the consequences of salmon‐derived nutrients by quantifying the condition and fitness of organisms putatively using those resources. 相似文献
5.
Kauri dieback, caused by Phytophthora agathidicida, is a biotic disturbance that poses a recent threat to the survival of kauri (Agathis australis) forests in New Zealand. Previous studies have shown that throughfall and stemflow play an important role in the kauri forests’ internal nutrient cycle. However, the effects of P. agathidicida infection on canopy and forest floor nutrient fluxes in kauri forests remain unknown. Here, we measured throughfall, stemflow and forest floor water yield, nutrient (potassium, calcium, magnesium, manganese, silicon, sulfur, sodium, iron) concentrations and fluxes of ten kauri trees differing in soil P. agathidicida DNA concentration, and health status. We did not observe an effect of soil P. agathidicida DNA concentration on throughfall, stemflow, and forest floor water yield. Throughfall and forest floor nutrient concentrations and fluxes decreased (up to 50%) with increasing soil P. agathidicida DNA concentration. We found significant effects on potassium and manganese fluxes in throughfall; calcium and silicon fluxes in forest floor leachate. A decline in canopy and forest floor nutrient fluxes may result in soil nutrient imbalances, which in turn may negatively impact forest productivity and may increase the susceptibility of trees to future pathogen infection in these ecologically unique kauri forests. Given our findings and the increasing spread of Phytophthora species worldwide, research on the underlying physiological mechanisms linking dieback and plant–soil nutrient fluxes is critical. 相似文献
6.
Abstract. 1. Little is known about the animals that scavenge invertebrates in the tropics and the impact of human activities on such organisms. 2. We studied the scavenging process using baits representing five dead invertebrate types in six habitats along an urbanisation gradient in equatorial Singapore: primary forest, old secondary forest, young secondary forest, recreational park, mown grassland and impervious surfaces. 3. Ants were the dominant scavengers, except at night in grassland when an earwig (Labiduridae) dominated. In general, the forest sites had more scavenger species and shorter bait survival times than the non‐forest habitats. 4. Bait survival time increased monotonically along the urbanisation gradient, suggesting that this parameter could be used as an indicator of habitat quality. 相似文献
7.
1. Cross‐ecosystem movements of resources, including detritus, nutrients and living prey, can strongly influence food web dynamics in recipient habitats. Variation in resource inputs is thought to be driven by factors external to the recipient habitat (e.g. donor habitat productivity and boundary conditions). However, inputs of or by ‘active’ living resources may be strongly influenced by recipient habitat quality when organisms exhibit behavioural habitat selection when crossing ecosystem boundaries. 2. To examine whether behavioural responses to recipient habitat quality alter the relative inputs of ‘active’ living and ‘passive’ detrital resources to recipient food webs, we manipulated the presence of caged predatory fish and measured biomass, energy and organic content of inputs to outdoor experimental pools of adult aquatic insects, frog eggs, terrestrial plant matter and terrestrial arthropods. 3. Caged fish reduced the biomass, energy and organic matter donated to pools by tree frog eggs by ～70%, but did not alter insect colonisation or passive allochthonous inputs of terrestrial arthropods and plant material. Terrestrial plant matter and adult aquatic insects provided the most energy and organic matter inputs to the pools (40–50%), while terrestrial arthropods provided the least (7%). Inputs of frog egg were relatively small but varied considerably among pools and over time (3%, range = 0–20%). Absolute and proportional amounts varied by input type. 4. Aquatic predators can strongly affect the magnitude of active, but not passive, inputs and that the effect of recipient habitat quality on active inputs is variable. Furthermore, some active inputs (i.e. aquatic insect colonists) can provide similar amounts of energy and organic matter as passive inputs of terrestrial plant matter, which are well known to be important. Because inputs differ in quality and the trophic level they subsidise, proportional changes in input type could have strong effects on recipient food webs. 5. Cross‐ecosystem resource inputs have previously been characterised as donor‐controlled. However, control by the recipient food web could lead to greater feedback between resource flow and consumer dynamics than has been appreciated so far. 相似文献
8.
Parasite–host interactions can drive periodic population dynamics when parasites overexploit host populations. The timing of host seasonal activity, or host phenology, determines the frequency and demographic impact of parasite–host interactions, which may govern whether parasites sufficiently overexploit hosts to drive population cycles. We describe a mathematical model of a monocyclic, obligate‐killer parasite system with seasonal host activity to investigate the consequences of host phenology on host–parasite dynamics. The results suggest that parasites can reach the densities necessary to destabilize host dynamics and drive cycling as they adapt, but only in some phenological scenarios such as environments with short seasons and synchronous host emergence. Furthermore, only parasite lineages that are sufficiently adapted to phenological scenarios with short seasons and synchronous host emergence can achieve the densities necessary to overexploit hosts and produce population cycles. Host‐parasite cycles also generate an eco‐evolutionary feedback that slows parasite adaptation to the phenological environment as rare advantageous phenotypes can be driven extinct due to a population bottleneck depending on when they are introduced in the cycle. The results demonstrate that seasonal environments can drive population cycling in a restricted set of phenological patterns and provide further evidence that the rate of adaptive evolution depends on underlying ecological dynamics. 相似文献
9.
Ioanna Salvarina 《Mammal Review》2016,46(2):131-143
- Many bats use aquatic habitats for foraging and for drinking water.
- Interactions between aquatic and terrestrial systems are important for understanding food web dynamics and for conserving species and ecosystems. Therefore, in this review, I examined the data available on bats’ use of aquatic habitats.
- The objectives of the present review were to evaluate the importance of aquatic resources for bats and to identify the effects that eutrophication, water pollution, and other anthropogenic impacts on water bodies have on bats.
- Most studies on bats and aquatic habitats have been conducted in Europe or in North America. They show, directly or indirectly, how bats use aquatic resources.
- Acoustic survey is the most common technique employed to assess habitat use by bats, although some researchers have used radio telemetry or other methods.
- Myotis daubentonii is the most commonly studied species. Within this topic, research does not tend to be focused more on threatened species.
- The effects of water pollution and eutrophication on bats remain unclear: different effects are reported for different species and in different areas.
- More studies are needed from Africa, South America, and Asia, regions for which few data are available, as well as from arid regions where fresh water is a limited resource.
10.
MICHAEL DOERING URS UEHLINGER THEKLA ACKERMANN MICHAEL WOODTLI KLEMENT TOCKNER 《Freshwater Biology》2011,56(7):1297-1311
1. In their natural state, river floodplains are composed of a complex mosaic of contrasting aquatic and terrestrial habitats. These habitats are expected to differ widely in their properties and corresponding ecological processes, although empirical data on their capacity to produce, store and transform organic matter and nutrients are limited. 2. The objectives of this study were (i) to quantify the spatiotemporal variation of respiration, a dominant carbon flux in ecosystems, in a complex river floodplain, (ii) to identify the environmental drivers of respiration within and among floodplain habitat types and (iii) to calculate whole‐floodplain respiration and to put these values into a global ecosystem context. 3. We measured soil and sediment respiration (sum of root and heterotrophic respiration; SR) throughout an annual cycle in two aquatic (pond and channel) and four terrestrial (gravel, large wood, vegetated island and riparian forest) floodplain habitat types in the island‐braided section of the near‐natural Tagliamento River (NE Italy). 4. Floodplain habitat types differed greatly in substratum composition (soil to coarse gravel), organic matter content (0.63 to 4.1% ash‐free dry mass) and temperature (seasonal range per habitat type: 8.6 to 33.1 °C). Average annual SR ranged from 0.54 ± 1.56 (exposed gravel) to 3.94 ± 3.72 μmol CO2 m?2 s?1 (vegetated islands) indicating distinct variation in respiration within and among habitat types. Temperature was the most important predictor of SR. However, the Q10 value ranged from 1.62 (channel habitat) to 4.57 (riparian forest), demonstrating major differences in habitat‐specific temperature sensitivity in SR. 5. Total annual SR in individual floodplain habitats ranged from 160 (ponds) to 1205 g C m?2 (vegetated islands) and spanned almost the entire range of global ecosystem respiration, from deserts to tropical forests. 相似文献
11.
Knowledge of aquatic food resources entering terrestrial systems is important for food web studies and conservation planning. Bats, among other terrestrial consumers, often profit from aquatic insect emergence and their activity might be closely related to such events. However, there is a lack of studies which monitor bat activity simultaneously with aquatic insect emergence, especially from lakes. Thus, our aim was to understand the relationship between insect emergence and bat activity, and investigate whether there is a general spatial or seasonal pattern at lakeshores. We assessed whole‐night bat activity using acoustic monitoring and caught emerging and aerial flying insects at three different lakes through three seasons. We predicted that insect availability and seasonality explain the variation in bat activity, independent of the lake size and characteristics. Spatial (between lakes) differences of bat activity were stronger than temporal (seasonal) differences. Bat activity did not always correlate to insect emergence, probably because other factors, such as habitat characteristics, or bats’ energy requirements, play an important role as well. Aerial flying insects explained bat activity better than the emerged aquatic insects in the lake with lowest insect emergence. Bats were active throughout the night with some activity peaks, and the pattern of their activity also differed among lakes and seasons. Lakes are important habitats for bats, as they support diverse bat communities and activity throughout the night and the year when bats are active. Our study highlights that there are spatial and temporal differences in bat activity and its hourly nocturnal pattern, that should be considered when investigating aquatic–terrestrial interactions or designing conservation and monitoring plans. 相似文献
12.
鲢鱼的放养对水质影响的研究进展 总被引：18，自引：0，他引：18
鲢鱼的放养对水质影响的研究进展董双林（华东师范大学生物系,上海２０００６２）ＥｆｆｅｃｔｏｆＳｉｌｖｅｒＣａｒｐＳｔｏｃｋｉｎｇｏｎＷａｔｅｒＱｕａｌｉｔｙｇ：ＲｅｓｅａｒｃｈＡｄｖａｎｃｅｓ．￥ＤｏｎｇＳｈｕａｎｇｌｉｎ（ＤｅｐａｒｔｍｅｎｔｏｆＢ... 相似文献
13.
Daniel Kleiner Ziva Shapiro Tuchman Fannia Shmulevich Anat Shahar Raz Zarivach Mickey Kosloff Shimon Bershtein 《Protein science : a publication of the Protein Society》2022,31(7)
Homomers are prevalent in bacterial proteomes, particularly among core metabolic enzymes. Homomerization is often key to function and regulation, and interfaces that facilitate the formation of homomeric enzymes are subject to intense evolutionary change. However, our understanding of the molecular mechanisms that drive evolutionary variation in homomeric complexes is still lacking. How is the diversification of protein interfaces linked to variation in functional regulation and structural integrity of homomeric complexes? To address this question, we studied quaternary structure evolution of bacterial methionine S‐adenosyltransferases (MATs)—dihedral homotetramers formed along a large and conserved dimeric interface harboring two active sites, and a small, recently evolved, interdimeric interface. Here, we show that diversity in the physicochemical properties of small interfaces is directly linked to variability in the kinetic stability of MAT quaternary complexes and in modes of their functional regulation. Specifically, hydrophobic interactions within the small interface of Escherichia coli MAT render the functional homotetramer kinetically stable yet impose severe aggregation constraints on complex assembly. These constraints are alleviated by electrostatic interactions that accelerate dimer‐dimer assembly. In contrast, Neisseria gonorrhoeae MAT adopts a nonfunctional dimeric state due to the low hydrophobicity of its small interface and the high flexibility of its active site loops, which perturbs small interface integrity. Remarkably, in the presence of methionine and ATP, N. gonorrhoeae MAT undergoes substrate‐induced assembly into a functional tetrameric state. We suggest that evolution acts on the interdimeric interfaces of MATs to tailor the regulation of their activity and stability to unique organismal needs. 相似文献
14.
Francisco Villamarín Timothy D. Jardine Stuart E. Bunn Boris Marioni William E. Magnusson 《Freshwater Biology》2017,62(8):1389-1400
- The structure of food webs may be strongly influenced by the distribution of top predators in space and time. The Amazon biome is the only region in the world where four alligatorid species are known to occur in sympatry, and they attain high densities in some regions. As top predators with a diverse range of prey species occupying different trophic levels, their impact upon food webs should be substantial, but the degree to which crocodilians differ in their food sources, and potentially avoid competitive exclusion where they occur syntopically is not well understood.
- Although most crocodilians are considered generalist opportunistic predators that feed on any source of protein available in the environment, Amazonian crocodilians show broad differences in the proportions of prey items they consume. It is believed that these differences may in part reflect habitat use, but it is unknown to what extent they represent interspecific differences in prey preferences or are a direct function of habitat selection.
- Stable carbon isotope data (δ13C) of crocodilians and their potential prey were used to assess differences in reliance on terrestrial versus aquatic resources. These data were then placed in a spatial context using classified maps that reflect habitat types (headwater streams, mid‐order flooded‐forest streams and várzea floodplains) to elucidate whether dietary differences are explained by habitat selection or are more likely a reflection of prey preferences.
- We found evidence for differences in types of basal resources supporting these crocodilians. Mean δ13C values were highest in Paleosuchus trigonatus (Schneider's dwarf caiman, ?25.7 ± 1.2‰), intermediate in Caiman crocodilus (spectacled caiman, ?27.4 ± 1.2‰) and Paleosuchus palpebrosus (Cuvier's dwarf caiman, ?27.7 ± 1.1‰) and lowest in Melanosuchus niger (black caiman, ?29.9 ± 1.3‰).
- A progressive decrease in δ13C values of crocodilian tissues occurred from headwaters to floodplains, which most likely reflects a progressive increase in autochthonous over allochthonous inputs in lower reaches of streams. The shift from terrestrial to aquatic resources sustaining these sympatric predators mirrors their spatial distribution along this ecotone. However, after taking into account the habitat in which pairs of syntopic individuals of distinct species occurred, significant differences in δ13C values suggest that P. trigonatus and P. palpebrosus have different prey bases. Thus, despite being opportunistic predators, our results show that differences in crocodilian diets likely result from prey preferences and not only from habitat selection. These findings suggest that some species of crocodilians may be less generalist than traditionally thought and their influence on terrestrial or aquatic food webs might be species specific.
15.
William S. Pearman Sarah J. Wells Olin K. Silander Nikki E. Freed James Dale 《Ecology and evolution》2020,10(24):13624
Population genetic structure in the marine environment can be influenced by life‐history traits such as developmental mode (biphasic, with distinct adult and larval morphology, and direct development, in which larvae resemble adults) or habitat specificity, as well as geography and selection. Developmental mode is thought to significantly influence dispersal, with direct developers expected to have much lower dispersal potential. However, this prediction can be complicated by the presence of geophysical barriers to dispersal. In this study, we use a panel of 8,020 SNPs to investigate population structure and biogeography over multiple spatial scales for a direct‐developing species, the New Zealand endemic marine isopod Isocladus armatus. Because our sampling range is intersected by two well‐known biogeographic barriers (the East Cape and the Cook Strait), our study provides an opportunity to understand how such barriers influence dispersal in direct developers. On a small spatial scale (20 km), gene flow between locations is extremely high, suggestive of an island model of migration. However, over larger spatial scales (600 km), populations exhibit a clear pattern of isolation‐by‐distance. Our results indicate that I. armatus exhibits significant migration across the hypothesized barriers and suggest that large‐scale ocean currents associated with these locations do not present a barrier to dispersal. Interestingly, we find evidence of a north‐south population genetic break occurring between Māhia and Wellington. While no known geophysical barrier is apparent in this area, it coincides with the location of a proposed border between bioregions. Analysis of loci under selection revealed that both isolation‐by‐distance and adaption may be contributing to the degree of population structure we have observed here. We conclude that developmental life history largely predicts dispersal in the intertidal isopod I. armatus. However, localized biogeographic processes can disrupt this expectation, and this may explain the potential meta‐population detected in the Auckland region. 相似文献
16.
Permafrost is experiencing climate warming at a rate that is two times faster than the rest of the Earth''s surface. However, it is still lack of a quantitative basis for predicting the functional stability of permafrost ecosystems in carbon (C) and nutrient cycling. We compiled the data of 708 observations from 89 air‐warming experiments in the Northern Hemisphere and characterized the general effects of temperature increase on permafrost C exchange and balance, biomass production, microbial biomass, soil nutrients, and vegetation N dynamics through a meta‐analysis. Also, an investigation was made on how responses might change with habitat‐specific (e.g., plant functional groups and soil moisture status) conditions and warming variables (e.g., warming phases, levels, and timing). The net ecosystem C exchange (NEE) was found to be downregulated by warming as a result of a stronger sensitivity to warming in respiration (15.6%) than in photosynthesis (6.2%). Vegetation usually responded to warming by investing more C to the belowground, as belowground biomass increased much more (30.1%) than aboveground biomass (2.9%). Warming had a minor effect on microbial biomass. Warming increased soil ammonium and nitrate concentrations. What''s more, a synthesis of 70 observations from 11 herbs and 9 shrubs revealed a 2.5% decline of N in green leaves. Compared with herbs, shrubs had a stronger response to respiration and had a decline in green leaf N to a greater extent. Not only in dry condition did green leaf N decline with warming but also in wet conditions. Warming in nongrowing seasons would negatively affect soil water, C uptake, and biomass production during growing seasons. Permafrost C loss and vegetation N decline may increase with warming levels and timing. Overall, these findings suggest that besides a positive C cycling–climate feedback, there will be a negative feedback between permafrost nutrient cycling and climate warming. 相似文献
17.
18.
Valter Bergant Shintaro Yamada Vincent Grass Yuta Tsukamoto Teresa Lavacca Karsten Krey Maria&#x;Teresa Mühlhofer Sabine Wittmann Armin Ensser Alexandra Herrmann Anja vom Hemdt Yuriko Tomita Shutoku Matsuyama Takatsugu Hirokawa Yiqi Huang Antonio Piras Constanze A Jakwerth Madlen Oelsner Susanne Thieme Alexander Graf Stefan Krebs Helmut Blum Beate M Kümmerer Alexey Stukalov Carsten B Schmidt&#x;Weber Manabu Igarashi Thomas Gramberg Andreas Pichlmair Hiroki Kato 《The EMBO journal》2022,41(17)
The SARS‐CoV‐2 infection cycle is a multistage process that relies on functional interactions between the host and the pathogen. Here, we repurposed antiviral drugs against both viral and host enzymes to pharmaceutically block methylation of the viral RNA 2''‐O‐ribose cap needed for viral immune escape. We find that the host cap 2''‐O‐ribose methyltransferase MTr1 can compensate for loss of viral NSP16 methyltransferase in facilitating virus replication. Concomitant inhibition of MTr1 and NSP16 efficiently suppresses SARS‐CoV‐2 replication. Using in silico target‐based drug screening, we identify a bispecific MTr1/NSP16 inhibitor with anti‐SARS‐CoV‐2 activity in vitro and in vivo but with unfavorable side effects. We further show antiviral activity of inhibitors that target independent stages of the host SAM cycle providing the methyltransferase co‐substrate. In particular, the adenosylhomocysteinase (AHCY) inhibitor DZNep is antiviral in in vitro, in ex vivo, and in a mouse infection model and synergizes with existing COVID‐19 treatments. Moreover, DZNep exhibits a strong immunomodulatory effect curbing infection‐induced hyperinflammation and reduces lung fibrosis markers ex vivo. Thus, multispecific and metabolic MTase inhibitors constitute yet unexplored treatment options against COVID‐19. 相似文献
19.
Endophytes are ubiquitous plant‐associated microbes and although they have the potential to alter the decomposition of infected leaf litter, this has not been well‐studied. The endophyte Rhytisma punctatum infects the leaves of Acer macrophyllum (bigleaf maple), causing the appearance of black ‘tar spots’ that persist in senesced leaves. Other foliar fungi also cause visible damage in healthy tissues of this host plant system including an unidentified bullseye‐shaped lesion, common in western Washington. Using three treatments of endophyte infection status in leaf tissue (R. punctatum‐infected, bullseye‐infected, lesion‐free), leaf litter discs were submerged in a third‐order temperate stream using mesh litter bags and harvested periodically over two months to determine the effects of litter treatment and incubation time on litter mass loss, fungal sporulation, and microbial community colonization. Litter containing symptomatic endophyte infections (Rhytisma or bullseye) had reduced sporulation of aquatic hyphomycetes, but decomposed significantly faster than lesion‐free or bullseye‐infected litter. Using amplicon‐based sequencing, we found a significant difference in bacterial communities colonizing Rhytisma‐infected and bullseye‐infected leaf litter, a significant difference in fungal communities colonizing Rhytisma‐infected leaf litter compared to the two other treatments, and a change in both community structure and relative abundances of bacterial and fungal taxa throughout the study period. Indicator Species Analysis clarified the drivers of these community shifts at the genus level. Our results show that endophyte‐associated, in‐stream sporulation and microbial community effects are observable within one species of leaf litter. 相似文献
20.
Chase A. Seltzner Justin D. Ferek James B. Thoden Hazel M. Holden 《Protein science : a publication of the Protein Society》2021,30(9):1882
Acanthamoeba polyphaga Mimivirus, a complex virus that infects amoeba, was first reported in 2003. It is now known that its DNA genome encodes for nearly 1,000 proteins including enzymes that are required for the biosynthesis of the unusual sugar 4‐amino‐4,6‐dideoxy‐d‐glucose, also known as d‐viosamine. As observed in some bacteria, the pathway for the production of this sugar initiates with a nucleotide‐linked sugar, which in the Mimivirus is thought to be UDP‐d‐glucose. The enzyme required for the installment of the amino group at the C‐4′ position of the pyranosyl moiety is encoded in the Mimivirus by the L136 gene. Here, we describe a structural and functional analysis of this pyridoxal 5′‐phosphate‐dependent enzyme, referred to as L136. For this analysis, three high‐resolution X‐ray structures were determined: the wildtype enzyme/pyridoxamine 5′‐phosphate/dTDP complex and the site‐directed mutant variant K185A in the presence of either UDP‐4‐amino‐4,6‐dideoxy‐d‐glucose or dTDP‐4‐amino‐4,6‐dideoxy‐d‐glucose. Additionally, the kinetic parameters of the enzyme utilizing either UDP‐d‐glucose or dTDP‐d‐glucose were measured and demonstrated that L136 is efficient with both substrates. This is in sharp contrast to the structurally related DesI from Streptomyces venezuelae, whose three‐dimensional architecture was previously reported by this laboratory. As determined in this investigation,DesI shows a profound preference in its catalytic efficiency for the dTDP‐linked sugar substrate. This difference can be explained in part by a hydrophobic patch in DesI that is missing in L136. Notably, the structure of L136 reported here represents the first three‐dimensional model for a virally encoded PLP‐dependent enzyme and thus provides new information on sugar aminotransferases in general. 相似文献