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An important goal of rice cultivar development is improvement of protein quality, especially with respect to essential amino acids such as methionine. With the goal of increasing seed methionine content, we generated Oryza sativa ssp. japonica cv. Taipei 309 transgenic lines expressing a feedback-desensitized CYSTATHIONINE GAMMA-SYNTHASE from Arabidopsis thaliana (AtD-CGS) under the control of the maize ubiquitin promoter. Despite persistently elevated cystathionine gamma-synthase (CGS) activity in the AtD-CGS transgenic lines relative to untransformed Taipei, sulfate was the only sulfur-containing compound found to be elevated throughout vegetative development. Accumulation of methionine and other sulfur-containing metabolites was limited to the leaves of young plants. Sulfate concentration was found to strongly and positively correlate with CGS activity across vegetative development, irrespective of whether the activity was provided by the endogenous rice CGS or by a combination of endogenous and AtD-CGS. Conversely, the concentrations of glutathione, valine, and leucine were clearly negatively correlated with CGS activity in the same tissues. We also observed a strong decrease in CGS activity in both untransformed Taipei and the AtD-CGS transgenic lines as the plants approached heading stage. The mechanism for this downregulation is currently unknown and of potential importance for efforts to increase methionine content in rice.
External temperature change has been shown to modify epigenetic patterns, such as DNA methylation, which regulates gene expression. DNA methylation is heritable, and as such provides a mechanism to convey environmental information to subsequent generations. Studies on epigenetic response to temperature increase are still scarce in wild mammals, even more so studies that compare tissue-specific epigenetic responses. Here, we aim to address differential epigenetic responses on a gene and gene pathway level in two organs, liver and testis. We chose these organs, because the liver is the main metabolic and thermoregulation organ, and epigenetic modifications in testis are potentially transmitted to the F2 generation. We focused on the transmission of DNA methylation changes to naive male offspring after paternal exposure to an ambient temperature increase of 10 degrees C, and investigated differential methylated regions of sons sired before and after the paternal exposure using Reduced Representation Bisulfite Sequencing. We detected both a highly tissue-specific epigenetic response, reflected in genes involved in organ-specific metabolic pathways, and a more general regulation of single genes epigenetically modified in both organs. We conclude that genomes are context-specifically differentially epigenetically regulated in response to temperature increase. These findings emphasize the epigenetic relevance in cell differentiation, which is essential for the specific function(s) of complex organs, and is represented in a diverse molecular regulation of genes and gene pathways. The results also emphasize the paternal contribution to adaptive processes.
Epigenetic modifications, of which DNA methylation is the best studied one, can convey environmental information through generations via parental germ lines. Past studies have focused on the maternal transmission of epigenetic information to the offspring of isogenic mice and rats in response to external changes, whereas heterogeneous wild mammals as well as paternal epigenetic effects have been widely neglected. In most wild mammal species, males are the dispersing sex and have to cope with differing habitats and thermal changes. As temperature is a major environmental factor we investigated if genetically heterogeneous Wild guinea pig (Cavia aperea) males can adapt epigenetically to an increase in temperature and if that response will be transmitted to the next generation(s). Five adult male guinea pigs (F0) were exposed to an increased ambient temperature for 2 months, i.e. the duration of spermatogenesis. We studied the liver (as the main thermoregulatory organ) of F0 fathers and F1 sons, and testes of F1 sons for paternal transmission of epigenetic modifications across generation(s). Reduced representation bisulphite sequencing revealed shared differentially methylated regions in annotated areas between F0 livers before and after heat treatment, and their sons’ livers and testes, which indicated a general response with ecological relevance. Thus, paternal exposure to a temporally limited increased ambient temperature led to an ‘immediate’ and ‘heritable’ epigenetic response that may even be transmitted to the F2 generation. In the context of globally rising temperatures epigenetic mechanisms may become increasingly relevant for the survival of species.
Epigenetic modifications are a mechanism conveying environmental information to subsequent generations via parental germ lines. Research on epigenetic responses to environmental changes in wild mammals has been widely neglected, as well as studies that compare responses to changes in different environmental factors. Here, we focused on the transmission of DNA methylation changes to naive male offspring after paternal exposure to either diet (~40% less protein) or temperature increase (10 °C increased temperature). Because both experiments focused on the liver as the main metabolic and thermoregulation organ, we were able to decipher if epigenetic changes differed in response to different environmental changes. Reduced representation bisulfite sequencing (RRBS) revealed differentially methylated regions (DMRs) in annotated genomic regions in sons sired before (control) and after the fathers’ treatments. We detected both a highly specific epigenetic response dependent on the environmental factor that had changed that was reflected in genes involved in specific metabolic pathways, and a more general response to changes in outer stimuli reflected by epigenetic modifications in a small subset of genes shared between both responses. Our results indicated that fathers prepared their offspring for specific environmental changes by paternally inherited epigenetic modifications, suggesting a strong paternal contribution to adaptive processes.
Epigenetic modifications, of which DNA methylation is the most stable, are a mechanism conveying environmental information to subsequent generations via parental germ lines. The paternal contribution to adaptive processes in the offspring might be crucial, but has been widely neglected in comparison to the maternal one. To address the paternal impact on the offspring’s adaptability to changes in diet composition, we investigated if low protein diet (LPD) in F0 males caused epigenetic alterations in their subsequently sired sons. We therefore fed F0 male Wild guinea pigs with a diet lowered in protein content (LPD) and investigated DNA methylation in sons sired before and after their father’s LPD treatment in both, liver and testis tissues. Our results point to a ‘heritable epigenetic response’ of the sons to the fathers’ dietary change. Because we detected methylation changes also in the testis tissue, they are likely to be transmitted to the F2 generation. Gene-network analyses of differentially methylated genes in liver identified main metabolic pathways indicating a metabolic reprogramming (‘metabolic shift’). Epigenetic mechanisms, allowing an immediate and inherited adaptation may thus be important for the survival of species in the context of a persistently changing environment, such as climate change.
First Steps towards the development of epigenetic biomarkers in female cheetahs (Acinonyx jubatus)
(2022)
Free-ranging cheetahs (Acinonyx jubatus) are generally healthy, whereas cheetahs under human care, such as those in zoological gardens, suffer from ill-defined infectious and degenerative pathologies. These differences are only partially explained by husbandry management programs because both groups share low genetic diversity. However, mounting evidence suggests that physiological differences between populations in different environments can be tracked down to differences in epigenetic signatures. Here, we identified differentially methylated regions (DMRs) between free-ranging cheetahs and conspecifics in zoological gardens and prospect putative links to pathways relevant to immunity, energy balance and homeostasis. Comparing epigenomic DNA methylation profiles obtained from peripheral blood mononuclear cells (PBMCs) from eight free-ranging female cheetahs from Namibia and seven female cheetahs living in zoological gardens within Europe, we identified DMRs of which 22 were hypermethylated and 23 hypomethylated. Hypermethylated regions in cheetahs under human care were located in the promoter region of a gene involved in host-pathogen interactions (KLC1) and in an intron of a transcription factor relevant for the development of pancreatic beta-cells, liver, and kidney (GLIS3). The most canonical mechanism of DNA methylation in promoter regions is assumed to repress gene transcription. Taken together, this could indicate that hypermethylation at the promoter region of KLC1 is involved in the reduced immunity in cheetahs under human care. This approach can be generalized to characterize DNA methylation profiles in larger cheetah populations under human care with a more granular longitudinal data collection, which, in the future, could be used to monitor the early onset of pathologies, and ultimately translate into the development of biomarkers with prophylactic and/or therapeutic potential.
Epigenetic mechanisms convey environmental information through generations and can regulate gene expression. Epigenetic studies in wild mammals are rare, but enable understanding adaptation processes as they may occur in nature. In most wild mammal species, males are the dispersing sex and thus often have to cope with differing habitats and thermal changes more rapidly than the often philopatric females. As temperature is a major environmental selection factor, we investigated whether genetically heterogeneous Wild guinea pig (Cavia aperea) males adapt epigenetically to an increase in temperature, whether that response will be transmitted to the next generation(s), and whether it regulates mRNA expression. Five (F0) adult male guinea pigs were exposed to an increased ambient temperature for 2 months, corresponding to the duration of the species' spermatogenesis. To study the effect of heat, we focused on the main thermoregulatory organ, the liver. We analyzed CpG-methylation changes of male offspring (F1) sired before and after the fathers' heat treatment (as has recently been described in Weyrich et al. [Mol. Ecol., 2015]). Transcription analysis was performed for the three genes with the highest number of differentially methylated changes detected: the thermoregulation gene Signal Transducer and Activator of Transcription 3 (Stat3), the proteolytic peptidase gene Cathepsin Z (Ctsz), and Sirtuin 6 (Sirt6) with function in epigenetic regulation. Stat3 gene expression was significantly reduced (P < 0.05), which indicated a close link between CpG-methylation and expression levels for this gene. The two other genes did not show gene expression changes. Our results indicate the presence of a paternal transgenerational epigenetic effect. Quick adaptation to climatic changes may become increasingly relevant for the survival of wildlife species as global temperatures are rising.
Citizen science projects have a long history in ecological studies. The research usefulness of such projects is dependent on applying simple and standardized methods. Here, we conducted a citizen science project that involved more than 3500 Swedish high school students to examine the temperature difference between surface water and the overlying air (T-w-T-a) as a proxy for sensible heat flux (Q(H)). If Q(H) is directed upward, corresponding to positive T-w-T-a, it can enhance CO2 and CH4 emissions from inland waters, thereby contributing to increased greenhouse gas concentrations in the atmosphere. The students found mostly negative T-w-T-a across small ponds, lakes, streams/rivers and the sea shore (i.e. downward Q(H)), with T-w-T-a becoming increasingly negative with increasing T-a. Further examination of T-w-T-a using high-frequency temperature data from inland waters across the globe confirmed that T-w-T-a is linearly related to T-a. Using the longest available high-frequency temperature time series from Lake Erken, Sweden, we found a rapid increase in the occasions of negative T-w-T-a with increasing annual mean T-a since 1989. From these results, we can expect that ongoing and projected global warming will result in increasingly negative T-w-T-a, thereby reducing CO2 and CH4 transfer velocities from inland waters into the atmosphere.
Epigenetic histone modulation contributes to improvements in inflammatory bowel disease via EBI3
(2020)
Ulcerative colitis (UC) is characterized by relapsing-remitting inflammatory episodes paralleled by varying cytokine levels, suggesting that switching epigenetic processes might be involved. However, the epigenetic impact on cytokine levels in colitis is mostly unexplored. The heterodimeric interleukin (IL)-12 cytokine family have various functions in both pro- and anti-inflammatory processes. The family member IL-35 (EBI3/IL-12p35) was recently reported to play an anti-inflammatory role in UC. Therefore, we aimed to investigate a possible epigenetic regulation of the IL-35 subunits in vitro and in vivo, and to examine the epigenetic targeting of EBI3 expression as a therapeutic option for UC. Exposure to either the pro-inflammatory TNF alpha or to histone deacetylase inhibitors (HDACi) significantly increased EBI3 expression in Human Colon Epithelial Cells (HCEC) generated from healthy tissue. When applied in combination, a drastic upregulation of EBI3 expression occurred, suggesting a synergistic mechanism. Consequently, IL-35 was increased as well. In vivo, the intestines of HDACi-treated wild-type mice exhibited reduced pathological signs of colitis compared to non-treated colitic mice. However, the improvement by HDACi treatment was completely lost in Ebi3-deficient mice (Ebi3(-/-)). In fact, HDACi appeared to exacerbate the disease phenotype in Ebi3(-/-). In conclusion, our results reveal that under inflammatory conditions, EBI3 is upregulated by the epigenetic mechanism of histone acetylation. The in vivo data show that the deficiency of EBI3 plays a key role in colitis manifestation. Concordantly, our data suggest that conditions promoting histone acetylation, such as upon HDACi application, improve colitis by a mechanism involving the local formation of the anti-inflammatory cytokine IL-35.
The creation of electron transfer (ET) chains based on the defined arrangement of enzymes and redox proteins on electrode surfaces represents an interesting approach within the field of bioelectrocatalysis. In this study, we investigated the ET reaction of the flavin-dependent enzyme fructose dehydrogenase (FDH) with the redox protein cytochrome c (cyt c). Two different pH optima were found for the reaction in acidic and neutral solutions. When cyt c was adsorbed on an electrode surface while the enzyme remained in solution, ET proceeded efficiently in media of neutral pH. Interprotein ET was also observed in acidic media; however, it appeared to be less efficient. These findings suggest that two different ET pathways between the enzyme and cyt c may occur. Moreover, cyt c and FDH were immobilized in multiple layers on an electrode surface by means of another biomacromolecule: DNA (double stranded) using the layer -by -layer technique. The biprotein multilayer architecture showed a catalytic response in dependence on the fructose concentration, indicating that the ET reaction between both proteins is feasible even in the immobilized state. The electrode showed a defined response to fructose and a good storage stability. Our results contribute to the better understanding of the ET reaction between FDH and cyt c and provide the basis for the creation of all-biomolecule based fructose sensors the sensitivity of which can be controlled by the layer preparation.
Hyenas (family Hyaenidae), as the sister group to cats (family Felidae), represent a deeply diverging branch within the cat-like carnivores (Feliformia). With an estimated population size of <10,000 individuals worldwide, the brown hyena (Parahyaena brunnea) represents the rarest of the four extant hyena species and has been listed as Near Threatened by the IUCN. Here, we report a high-coverage genome from a captive bred brown hyena and both mitochondrial and low-coverage nuclear genomes of 14 wild-caught brown hyena individuals from across southern Africa. We find that brown hyena harbor extremely low genetic diversity on both the mitochondrial and nuclear level, most likely resulting from a continuous and ongoing decline in effective population size that started similar to 1 Ma and dramatically accelerated towards the end of the Pleistocene. Despite the strikingly low genetic diversity, we find no evidence of inbreeding within the captive bred individual and reveal phylogeographic structure, suggesting the existence of several potential subpopulations within the species.
The bat-eared fox, Otocyon megalotis, is the only member of its genus and is thought to occupy a basal position within the dog family. These factors can lead to challenges in complete mitochondrial reconstructions and accurate phylogenetic positioning. Here, we present the first complete mitochondrial genome of the bat-eared fox recovered using shotgun sequencing and iterative mapping to three distantly related species. Phylogenetic analyses placed the bat-eared fox basal in the Canidae family within the clade including true foxes (Vulpes) and the raccoon dog (Nyctereutes) with high support values. This position is in good agreement with previously published results based on short fragments of mitochondrial and nuclear genes, therefore adding more support to the basal positioning of the bat-eared fox within Canidae.
The unusual mix of morphological traits displayed by extinct South American native ungulates (SANUs) confounded both Charles Darwin, who first discovered them, and Richard Owen, who tried to resolve their relationships. Here we report an almost complete mitochondrial genome for the litoptern Macrauchenia. Our dated phylogenetic tree places Macrauchenia as sister to Perissodactyla, but close to the radiation of major lineages within Laurasiatheria. This position is consistent with a divergence estimate of B66Ma (95% credibility interval, 56.64-77.83 Ma) obtained for the split between Macrauchenia and other Panperissodactyla. Combined with their morphological distinctiveness, this evidence supports the positioning of Litopterna (possibly in company with other SANU groups) as a separate order within Laurasiatheria. We also show that, when using strict criteria, extinct taxa marked by deep divergence times and a lack of close living relatives may still be amenable to palaeogenomic analysis through iterative mapping against more distant relatives.
Determining covalent and charge-transfer contributions to bonding in solution has remained an experimental challenge. Here, the quenching of fluorescence decay channels as expressed in dips in the L-edge X-ray spectra of solvated 3d transition-metal ions and complexes was reported as a probe. With a full set of experimental and theoretical ab initio L-edge X-ray spectra of aqueous Cr3+, including resonant inelastic X-ray scattering, we address covalency and charge transfer for this prototypical transition-metal ion in solution. We dissect local atomic effects from intermolecular interactions and quantify X-ray optical effects. We find no evidence for the asserted ultrafast charge transfer to the solvent and show that the dips are readily explained by X-ray optical effects and local atomic state dependence of the fluorescence yield. Instead, we find, besides ionic interactions, a covalent contribution to the bonding in the aqueous complex of ligand-to-metal charge-transfer character.
Wind influences the development, architecture and morphology of plant roots and may modify subsequent interactions between plants and soil (plant–soil feedbacks—PSFs). However, information on wind effects on fine root morphology is scarce and the extent to which wind changes plant–soil interactions remains unclear. Therefore, we investigated the effects of two wind intensity levels by manipulating surrounding vegetation height in a grassland PSF field experiment. We grew four common plant species (two grasses and two non-leguminous forbs) with soil biota either previously conditioned by these or other species and tested the effect of wind on root:shoot ratio, fine root morphological traits as well as the outcome for PSFs. Wind intensity did not affect biomass allocation (i.e. root:shoot ratio) in any species. However, fine-root morphology of all species changed under high wind intensity. High wind intensity increased specific root length and surface area and decreased root tissue density, especially in the two grasses. Similarly, the direction of PSFs changed under high wind intensity in all four species, but differences in biomass production on the different soils between high and low wind intensity were marginal and most pronounced when comparing grasses with forbs. Because soils did not differ in plant-available nor total nutrient content, the results suggest that wind-induced changes in root morphology have the potential to influence plant–soil interactions. Linking wind-induced changes in fine-root morphology to effects on PSF improves our understanding of plant–soil interactions under changing environmental conditions.
Enzyme immobilization using nanomaterials offers new approaches to enhanced bioelectrochemical performance and is essential for the preparation of bioelectrodes with high reproducibility and low cost. In this report, we describe the development of new three-dimensional (3D) bioelectrodes by immobilizing a "bioink" of glucose oxidase (GOD) in a matrix of reduced graphene oxides (RGOs), polyethylenimine (PEI), and ferrocene carboxylic acid (FcCOOH) on carbon paper (CP). CP with 3D interwoven carbon fibers serves as a solid porous and electronically conducting skeleton, providing large surface areas and space for loading the bioink and diffusion of substrate molecules, respectively. RGO enhances contact between the GOD-matrix and CP, maintaining high conductivity. The composition of the bioink has been systematically optimized. The GOD bioelectrodes show linearly increasing electrocatalytic oxidation current toward glucose concentration up to 48 mM. A hybrid enzymatic biofuel cell equipped with the GOD bioelectrode as a bioanode and a platinum cathode furthermore registers a maximum power density of 5.1 mu W cm(-2) and an open circuit voltage of 0.40 V at 25 degrees C. The new method reported of preparing a bioelectrode by drop-casting the bioink onto the substrate electrode is facile and versatile, with the potential of application also for other enzymatic bioelectrodes.
Simple Summary:& nbsp;High alpine meadows are home to numerous endemic butterfly species. A combination of climate change and changes in agricultural practices has led to a severe decline in many species. A seemingly unaffected representative of this habitat is Erebia pronoe. We studied the behaviour, resource use and population structure of this species to explain its resilience and estimate its future survival potential. This species shows pronounced protandry in combination with serial eclosion. Males were significantly more active and mobile and were also caught significantly more often than females, resulting in a pronounced shift in sex ratio in the predicted population structure. The adults use a wide range of nectar plants and establish homeranges in areas of high habitat quality. Thus, Erebia pronoe adults use a wide array of resources combined with a slight specialisation to avoid niche overlap with closely related species. The resulting ecological flexibility seems to be an adaptation to unpredictable environmental conditions, which should be the result of a long-lasting adaptation process. Moreover, the combination of opportunism and modest specialisation should also be a good basis for coping with future changes caused by climate and land-use change.</p> <br /> <br></p> <br /> A mark-recapture study of the nominotypical Erebia pronoe in the Alps was conducted to survey its ecological demands and characteristics. Population structure analysis revealed a combination of protandry (one-week earlier eclosion of males) and serial eclosion. Significant differences between both sexes were found in population density (males: 580/ha & PLUSMN; 37 SE; females: 241/ha & PLUSMN; 66 SE), sex-ratio (2.4) and behaviour (57.7 vs. 11.9% flying). Both sexes used a wide range of nectar plants (Asteraceae, 77.3%; Dipsacaceae, 12.3%; Gentianaceae, 9.7%). The use of nectar plants shows a non-specific spectrum, which, however, completely avoids overlap with the locally co-occurring species Erebia nivalis. Movement patterns show the establishment of homeranges, which significantly limits the migration potential. Due to its broad ecological niche, E. pronoe will probably be able to react plastically to the consequences of climate change. The formation of high population densities, the unconcerned endangerment status, the unspecific resource spectrum and the sedentary character of the species make E. pronoe a potential indicator of the quality and general resource occurrence of alpine rupicolous grasslands.
Several morphological and mitochondrial lineages of the alpine ringlet butterfly species Erebia pronoe have been described, indicating a complex phylogenetic structure. However, the existing data were insufficient and allow neither a reconstruction of the biogeographic history, nor an assessment of the genetic lineages. Therefore, we analysed mitochondrial (COI, NDI) and nuclear (EF1 alpha, RPS5) gene sequences and compared them with sequences from the sister species Erebia melas. Additionally, we combined this information with morphometric data of the male genitalia and the infection patterns with Wolbachia strains, based on a WSP analysis. We obtained a distinct phylogeographic structure within the E. pronoe-melas complex with eight well-distinguishable geographic groups, but also a remarkable mito-nuclear discordance. The mito-nuclear discordance in E. melas and E. pronoe glottis can be explained by different ages of Wolbachia infections with different Wolbachia strains, associated selective sweeps, and hybridisation inhibition. Additionally, we found indications for incipient speciation of E. pronoe glottis in the Pyrenees and a pronounced range dynamic within and among the other high mountain systems of Europe. Our results emphasize the importance of combined approaches in reconstructing biogeographic patterns and evaluating phylogeographic splits.
Proteasomes are key proteases in regulating protein homeostasis. Their holo-enzymes are composed of 40 different subunits which are arranged in a proteolytic core (CP) flanked by one to two regulatory particles (RP). Proteasomal proteolysis is essential for the degradation of proteins which control time-sensitive processes like cell cycle progression and stress response. In dividing yeast and human cells, proteasomes are primarily nuclear suggesting that proteasomal proteolysis is mainly required in the nucleus during cell proliferation. In yeast, which have a closed mitosis, proteasomes are imported into the nucleus as immature precursors via the classical import pathway. During quiescence, the reversible absence of proliferation induced by nutrient depletion or growth factor deprivation, proteasomes move from the nucleus into the cytoplasm. In the cytoplasm of quiescent yeast, proteasomes are dissociated into CP and RP and stored in membrane-less cytoplasmic foci, named proteasome storage granules (PSGs). With the resumption of growth, PSGs clear and mature proteasomes are transported into the nucleus by Blm10, a conserved 240 kDa protein and proteasome-intrinsic import receptor. How proteasomes are exported from the nucleus into the cytoplasm is unknown.
Die Professionsorientierung der Lehramtsstudiengänge ist ein zentrales Anliegen der universitären Potsdamer Lehrkräftebildung. Seit 1999 finden Evaluationen zur Professionsorientierung statt, die Diskrepanzen zwischen der gewünschten und der erfahrenen Professionsorientierung durch die Studierenden aufzeigen. Im Wintersemester 2013/14 wurden neue Studiengänge an der Universität Potsdam eingeführt. Inwieweit damit auch eine stärkere Professionsorientierung und ein stärkerer Berufsbezug erfolgt ist, ist bislang ungeklärt. In einer Onlinebefragung im Dezember 2018 wurden Studierende der Lehramtsstudiengänge der Universität Potsdam gebeten, die inhaltliche Gestaltung der Lehramtsstudiengänge sowie die Professionsorientierung der Praxisphasen, die Betreuung und Beratung im Rahmen der Praktika, den Nutzen der Praktika für Studium und Beruf und ihre Lehrer:innenkompetenz einzuschätzen. Der Beitrag stellt erste empirische Analysen dar und diskutiert Anregungen zur Weiterentwicklung der Studiengänge mit Bezug auf die Praxisstudien.
COMMIT
(2022)
Composition and functions of microbial communities affect important traits in diverse hosts, from crops to humans. Yet, mechanistic understanding of how metabolism of individual microbes is affected by the community composition and metabolite leakage is lacking. Here, we first show that the consensus of automatically generated metabolic reconstructions improves the quality of the draft reconstructions, measured by comparison to reference models. We then devise an approach for gap filling, termed COMMIT, that considers metabolites for secretion based on their permeability and the composition of the community. By applying COMMIT with two soil communities from the Arabidopsis thaliana culture collection, we could significantly reduce the gap-filling solution in comparison to filling gaps in individual reconstructions without affecting the genomic support. Inspection of the metabolic interactions in the soil communities allows us to identify microbes with community roles of helpers and beneficiaries. Therefore, COMMIT offers a versatile fully automated solution for large-scale modelling of microbial communities for diverse biotechnological applications. <br /> Author summaryMicrobial communities are important in ecology, human health, and crop productivity. However, detailed information on the interactions within natural microbial communities is hampered by the community size, lack of detailed information on the biochemistry of single organisms, and the complexity of interactions between community members. Metabolic models are comprised of biochemical reaction networks based on the genome annotation, and can provide mechanistic insights into community functions. Previous analyses of microbial community models have been performed with high-quality reference models or models generated using a single reconstruction pipeline. However, these models do not contain information on the composition of the community that determines the metabolites exchanged between the community members. In addition, the quality of metabolic models is affected by the reconstruction approach used, with direct consequences on the inferred interactions between community members. Here, we use fully automated consensus reconstructions from four approaches to arrive at functional models with improved genomic support while considering the community composition. We applied our pipeline to two soil communities from the Arabidopsis thaliana culture collection, providing only genome sequences. Finally, we show that the obtained models have 90% genomic support and demonstrate that the derived interactions are corroborated by independent computational predictions.
Rhizophagus irregularis is one of the most extensively studied arbuscular mycorrhizal fungi (AMF) that forms symbioses with and improves the performance of many crops. Lack of transformation protocol for R. irregularis renders it challenging to investigate molecular mechanisms that shape the physiology and interactions of this AMF with plants.
Here, we used all published genomics, transcriptomics, and metabolomics resources to gain insights into the metabolic functionalities of R. irregularis by reconstructing its high-quality genome-scale metabolic network that considers enzyme constraints. Extensive validation tests with the enzyme-constrained metabolic model demonstrated that it can be used to (i) accurately predict increased growth of R. irregularis on myristate with minimal medium; (ii) integrate enzyme abundances and carbon source concentrations that yield growth predictions with high and significant Spearman correlation (rS = 0.74) to measured hyphal dry weight; and (iii) simulate growth rate increases with tighter association of this AMF with the host plant across three fungal structures.
Based on the validated model and system-level analyses that integrate data from transcriptomics studies, we predicted that differences in flux distributions between intraradical mycelium and arbuscles are linked to changes in amino acid and cofactor biosynthesis.
Therefore, our results demonstrated that the enzyme-constrained metabolic model can be employed to pinpoint mechanisms driving developmental and physiological responses of R. irregularis to different environmental cues.
In conclusion, this model can serve as a template for other AMF and paves the way to identify metabolic engineering strategies to modulate fungal metabolic traits that directly affect plant performance.
IMPORTANCE Mounting evidence points to the benefits of the symbiotic interactions between the arbuscular mycorrhiza fungus Rhizophagus irregularis and crops; however, the molecular mechanisms underlying the physiological responses of this fungus to different host plants and environments remain largely unknown.
We present a manually curated, enzyme-constrained, genome-scale metabolic model of R. irregularis that can accurately predict experimentally observed phenotypes.
We show that this high-quality model provides an entry point into better understanding the metabolic and physiological responses of this fungus to changing environments due to the availability of different nutrients.
The model can be used to design metabolic engineering strategies to tailor R. irregularis metabolism toward improving the performance of host plants.
The rewetting of drained peatlands alters peat geochemistry and often leads to sustained elevated methane emission. Although this methane is produced entirely by microbial activity, the distribution and abundance of methane-cycling microbes in rewetted peatlands, especially in fens, is rarely described. In this study, we compare the community composition and abundance of methane-cycling microbes in relation to peat porewater geochemistry in two rewetted fens in northeastern Germany, a coastal brackish fen and a freshwater riparian fen, with known high methane fluxes. We utilized 16S rRNA high-throughput sequencing and quantitative polymerase chain reaction (qPCR) on 16S rRNA, mcrA, and pmoA genes to determine microbial community composition and the abundance of total bacteria, methanogens, and methanotrophs. Electrical conductivity (EC) was more than 3 times higher in the coastal fen than in the riparian fen, averaging 5.3 and 1.5 mS cm(-1), respectively. Porewater concentrations of terminal electron acceptors (TEAs) varied within and among the fens. This was also reflected in similarly high intra- and inter-site variations of microbial community composition. Despite these differences in environmental conditions and electron acceptor availability, we found a low abundance of methanotrophs and a high abundance of methanogens, represented in particular by Methanosaetaceae, in both fens. This suggests that rapid (re) establishment of methanogens and slow (re) establishment of methanotrophs contributes to prolonged increased methane emissions following rewetting.
Electrochemical polymerization of functionalized thiohene derivatives for immobilization of proteins
(1997)
Silvicultural practices lead to changes in forest composition and structure and may impact species diversity from the overall regional species pool to stand-level species occurrence. We explored to what extent fine-scale occupancy patterns in differently managed forest stands are driven by environment and ecological traits in three regions in Germany using a multi-species hierarchical model. We tested for the possible impact of environmental variables and ecological traits on occupancy dynamics in a joint modelling exercise while taking possible variation in coefficient estimates over years and plots into account. Bird species richness differed across regions and years, and trends in species richness across years were different in the three regions. On the species level, forest management affected occupancy of species in all regions, but only 35% of the total assemblage-level variation in occurrence probability was explained by either forest type and successional stage and <?1% by forest edge. On the assemblage level, bird occurrence decreased with body mass in all regions. Species with smaller breeding ranges had lower occurrence probabilities in one region, while later spring arrival decreased occurrence probabilities in the two other regions. Spatial variation in the effect size of trait covariates such as species phylogeny and breeding strata showed that variation in patch occupancy due to fine-scale differences in forest management is, to some extent, predictable from ecological traits. Our results show that environmental factors and ecological traits jointly predict variation in bird occupancy patterns and their response to forest management. Observations at the fine scale of forest stands, at which conservation efforts can be arranged along with forest management practices in heterogeneous environments, have been shown to provide meaningful insights despite the difficulties involved in monitoring mobile organisms such as birds at the plot level.
Hantaviruses are enveloped viruses that possess a tri-segmented, negative-sense RNA genome.
The viral S-segment encodes the multifunctional nucleocapsid protein (N), which is involved in genome packaging, intracellular protein transport, immunoregulation, and several other crucial processes during hantavirus infection.
In this study, we generated fluorescently tagged N protein constructs derived from Puumalavirus (PUUV), the dominant hantavirus species in Central, Northern, and Eastern Europe.
We comprehensively characterized this protein in the rodent cell line CHO-K1, monitoring the dynamics of N protein complex formation and investigating co-localization with host proteins as well as the viral glycoproteins Gc and Gn.
We observed formation of large, fibrillar PUUV N protein aggregates, rapidly coalescing from early punctate and spike-like assemblies.
Moreover, we found significant spatial correlation of N with vimentin, actin, and P-bodies but not with microtubules. N constructs also co-localized with Gn and Gc albeit not as strongly as the glycoproteins associated with each other.
Finally, we assessed oligomerization of N constructs, observing efficient and concentration-dependent multimerization, with complexes comprising more than 10 individual proteins.
Activated carbon has become a widely used tool to investigate root-mediated allelopathy of plants, especially in plant invasion biology, because it adsorbs and thereby neutralizes root exudates. Allelopathy has been a controversially debated phenomenon for years, which revived in plant invasion biology as one possible reason for the success of invasive plants. Noxious plant exudates may harm other plants and provide an advantage to the allelopathic plant. However, root exudates are not always toxic, but may stimulate the microbial community and change nutrient availability in the rhizosphere. In a greenhouse experiment, we investigated the interacting effects of activated carbon, arbuscular mycorrhiza and plant competition between the invasive Senecio inaequidens and the native Artemisia vulgaris. Furthermore, we tested whether activated carbon showed any undesired effects by directly affecting mycorrhiza or soil chemistry. Contrary to the expectation, S. inaequidens was a weak competitor and we could not support the idea that allelopathy was involved in the competition. Activated carbon led to a considerable increase in the aboveground biomass production and reduced the infection with arbuscular mycorrhiza of both plant species. We expected that arbuscular mycorrhiza promotes plant growth by increasing nutrient availability, but we found the contrary when activated carbon was added. Chemical analyses of the substrate showed, that adding activated carbon resulted in a strong increase in plant available phosphate and in a decrease of the C-organic/N-total ration both of which suggest stimulated microbial activity. Thus, activated carbon not only reduced potential allelopathic effects, but substantially changed the chemistry of the substrate. These results show that activated carbon should be handled with great care in ecological experiments on allelopathy because of possible confounding effects on the soil community.
Changes in land-use are supposed to be among the severest prospective threats to plant diversity worldwide. In semi-natural temperate grasslands, the cessation of traditional land use like livestock grazing is considered to be one of the most important drivers of the diversity loss witnessed within the last decades. Despite of the enormous number of studies on successional pathways following grazing abandonment there is no general pattern of how grassland communities are affected in terms of diversity, trait composition and pace of succession. To gain a comprehensive picture is difficult given the heterogeneity of environments and the time and effort needed for long-term investigations. We here use a proven individual- and trait-based grassland community model to analyze short- and long-term consequences of grazing abandonment under different assumptions of resource availability, pre-abandonment grazing intensity and regional isolation of communities.
Grazing abandonment led to a decrease of plant functional type (PFT) diversity in all but two scenarios in the long-term. In short-term we also found an increase or no change in Shannon diversity for several scenarios. With grazing abandonment we overall found an increase in maximum plant mass, clonal integration and longer lateral spread, a decrease in rosette plant types and in stress tolerant plants, as well as an increase in grazing tolerant and a decrease in grazing avoiding plant types. Observed changes were highly dependent on the regional configuration of communities, prevalent resource conditions and land use intensity before abandonment. While long-term changes took around 10-20 years in resource rich conditions, new equilibria established in resource poor conditions only after 30-40 years.
Our results confirm the potential threats caused by recent land-use changes and the assumption that oligotrophic communities are more resistant than mesotrophic communities also for long-term abandonment. Moreover, results revealed that species-rich systems are not per se more resistant than species-poor grasslands. (C) 2015 Elsevier B.V. All rights reserved.
Harnessing the evolvability of tricyclic microviridins to dissect protease-inhibitor interactions
(2014)
Understanding and controlling proteolysis is an important goal in therapeutic chemistry. Among the natural products specifically inhibiting proteases microviridins are particularly noteworthy. Microviridins are ribosomally produced and posttranslationally modified peptides that are processed into a unique, cagelike architecture. Here, we report a combined rational and random mutagenesis approach that provides fundamental insights into selectivity-conferring moieties of microviridins. The potent variant microviridin J was co-crystallized with trypsin, and for the first time the three-dimensional structure of microviridins was determined and the mode of inhibition revealed.
Microviridins are unique protease inhibitors from bloom-forming cyanobacteria that have both ecological and pharmacological relevance. Their peptide backbones are produced ribosomally, and ATP grasp ligases introduce omega-ester and omega-amide bonds to yield rare cage-like structures. Bioinformatic analysis of the microviridin biosynthesis gene cluster suggests a novel type of processing machinery, which could rationalize the challenging in vivo/in vitro reconstitution of the pathway. In this work, we report the establishment of a minimal expression system for microviridins. Through bioinformatics and mutational analysis of the MdnA leader peptide we identified and characterized a strictly conserved binding motif that is specific for microviridin ligases. Furthermore, we showed that the ABC transporter MdnE is crucial for cyclization and processing of microviridins and demonstrated that MdnE is essential for stability of the microviridin biosynthesis complex.
Phytoplankton dynamics in a shallow eutrophic lake were investigated over a 3-year period with respect to environmental forces which drive species composition and diversity. Diversity was calculated on the basis of species as well as on the basis of their functional properties (the C-R-S-concept). Stratification and water column mixing had a strong impact on phytoplankton composition. Application of a similarity-diversity model revealed that a high diversity was a transient non-stable state, whereas drastic changes or long-lasting stable environmental conditions are characterized by low diversity. This effect was more pronounced when the diversity was calculated on the basis of the phytoplankton species functional properties. Thus, this functional approach supports the intermediate disturbance hypothesis from field data.
The mode of nutrition of mixotrophic flagellates determines the food quality for their consumers
(2007)
The invasion success of the cyanobacterium Cylindrospermopsis raciborskii in experimental mesocosms
(2017)
The potentially toxic, invasive cyanobacterium Cylindrospermopsis raciborskii, originating from sub-tropical regions, has spread into temperate climate zones in almost all continents. Potential factors in its success are temperature, light and nutrient levels. Grazing losses through zooplankton have been measured in the laboratory but are typically not regarded as a factor in (failed) invasion success. In some potentially suitable lakes, C. raciborskii has never been found, although it is present in water bodies close by. Therefore, we tested the invasive potential of three different isolates introduced into natural plankton communities using laboratory mesocosm experiments under three grazing levels: ambient zooplankton densities, removal of large species using 100 mu m mesh and a ca. doubling of large species. Three C. raciborskii isolates originating from the same geographic region (North-East Germany) were added separately to the four replicates of each treatment and kept in semi-continuous cultures for 21 days. Two isolates disappeared from the mesocosms and were also not viable in filtered lake water indicating that the lake water itself or the switch from culture medium to lake water led to the decay of the inoculated C. raciborskii. Only one out of the three isolates persisted in the plankton communities at a rather low level and only in the treatment without larger zooplankton. This result demonstrates that under potentially suitable environmental conditions, top-down control from zooplankton might hamper the establishment of C. raciborskii. Non-metric multidimensional scaling showed distinct variation in resident phytoplankton communities between the different grazing levels, thus differential grazing impact shaped the resident community in different ways allowing C. raciborskii only to invade under competitive (= low grazing pressure) conditions. Furthermore, even after invasion failure, the temporary presence of C. raciborskii influenced the phytoplankton community.
In most biodiversity studies, taxonomic diversity is the measure for the multiplicity of species and is often considered to represent functional diversity. However, trends in taxonomic diversity and functional diversity may differ, for example, when many functionally similar but taxonomically different species co-occur in a community. The differences between these diversity measures are of particular interest in diversity research for understanding diversity patterns and their underlying mechanisms. We analysed a temporally highly resolved 20-year time series of lake phytoplankton to determine whether taxonomic diversity and functional diversity exhibit similar or contrasting seasonal patterns. We also calculated the functional mean of the community in n-dimensional trait space for each sampling day to gain further insights into the seasonal dynamics of the functional properties of the community. We found an overall weak positive relationship between taxonomic diversity and functional diversity with a distinct seasonal pattern. The two diversity measures showed synchronous behaviour from early spring to mid-summer and a more complex and diverging relationship from autumn to late winter. The functional mean of the community exhibited a recurrent annual pattern with the most prominent changes before and after the clear-water phase. From late autumn to winter, the functional mean of the community and functional diversity were relatively constant while taxonomic diversity declined, suggesting competitive exclusion during this period. A further decline in taxonomic diversity concomitant with increasing functional diversity in late winter to early spring is seen as a result of niche diversification together with competitive exclusion. Under these conditions, several different sets of traits are suitable to thrive, but within one set of functional traits only one, or very few, morphotypes can persist. Taxonomic diversity alone is a weak descriptor of trait diversity in phytoplankton. However, the combined analysis of taxonomic diversity and functional diversity, along with the functional mean of the community, allows for deeper insights into temporal patterns of community assembly and niche diversification.
Lake morphometry and wind exposure may shape the plankton community structure in acidic mining lakes
(2010)
Acidic mining lakes (pH <3) are specific habitats exhibiting particular chemical and biological characteristics. The species richness is low and mixotrophy and omnivory are common features of the plankton food web in such lakes. The plankton community structure of mining lakes of different morphometry and mixing type but similar chemical characteristics (Lake 130, Germany and Lake Langau, Austria) was investigated. The focus was laid on the species composition, the trophic relationship between the phago-mixotrophic flagellate Ochromonas sp. and bacteria and the formation of a deep chlorophyll maximum along a vertical pH-gradient. The shallow wind-exposed Lake 130 exhibited a higher species richness than Lake Langau. This increase in species richness was made up mainly by mero-planktic species, suggesting a strong benthic/littoral - pelagic coupling. Based on the field data from both lakes, a nonlinear, negative relation between bacteria and Ochromonas biomass was found, suggesting that at an Ochromonas biomass below 50 mu g CL-1. the grazing pressure on bacteria is low and with increasing Ochromonas biomass bacteria decline. Furthermore, in Lake Langau, a prominent deep chlorophyll maximum was found with chlorophyll concentrations ca. 50 times higher than in the epilimnion which was build up by the euglenophyte Lepocinclis sp. We conclude that lake morphometry, and specific abiotic characteristics such as mixing behaviour influence the community structure in these mining lakes.
Water column mixing is known to have a decisive impact on plankton communities. The underlying mechanisms depend on the size and depth of the water body, the nutrient status, and the plankton community structure and they are well understood for shallow polymictic and deep stratified lakes. Two consecutive mixing events of similar intensity under different levels of herbivory were performed in enclosures in a shallow, but periodically stratified, eutrophic lake, in order to investigate the effects of water column mixing on bacteria abundance, phytoplankton abundance and diversity, and rotifer abundance and fecundity. When herbivory by filter-feeding zooplankton was low, water column mixing provoking a substantial nutrient input into the euphotic zone, led to an intense net increase of bacteria and phytoplankton biomass. Phytoplankton diversity was lower in the mixed enclosures than in the undisturbed ones owing to the larger contribution of a few fast-growing species. After the second mixing event at high biomass of filter-feeding crustaceans, the increase of phytoplankton biomass was lower than after the first mixing, and diversity remained unchanged as the enhanced growth of small fast-growing was prevented by zooplankton grazing. Bacteria abundance did not increase after the second mixing, when cladoceran biomass was high. Rotifer fecundity indicated a transmission of the phytoplankton response to the next trophic level. Our results suggest that water column mixing in shallow eutrophic lakes with periodic stratification has a strong effect on the plankton community by enhanced nutrient availability rather than resuspension or reduced light availability. This fuels the basis of the classic and microbial food chain via enhanced phytoplankton and bacteria growth, but the effects on biomass may be dampened by high levels of herbivory.
Planktische Räuber-Beute-Systeme : experimentelle Untersuchungen von ökologischen Synchronisationen
(2000)
Trait-based approaches have become increasingly successful in community ecology. They assume that the distribution of functional traits within communities responds in a predictable way to alterations in environmental forcing and that strong forcing may accelerate such trait changes. We used high frequency measurements of phytoplankton to test these assumptions. We analyzed the seasonal and long-term dynamics of the community trait mean within a multi-dimensional trait space under alternating multifactorial environmental conditions. The community trait mean exhibited a distinct recurrent annual pattern that reflected minor changes in climate, herbivory and nutrients. Independent of early spring conditions, the community trait mean was repeatedly driven into a narrow confined area in the trait space under pronounced herbivory during the clear water phase. The speed of movement was highest at the onset and the relaxation of such strong unidirectional forcing. Thus, our data support the conceptual framework of trait-based ecology that alterations in environmental conditions are systematically tracked by adjustments in the dominant functional trait values and that the speed of trait changes depends on the kind and intensity of the selection pressure. Our approach provides a sensitive tool to detect small functional differences in the community related to subtle differences in forcing.
Extreme habitats often harbor specific communities that differ substantially from non-extreme habitats. In many cases, these communities are characterized by archaea, bacteria and protists, whereas the number of species of metazoa and higher plants is relatively low. In extremely acidic habitats, mostly prokaryotes and protists thrive, and only very few metazoa thrive, for example, rotifers. Since many studies have investigated the physiology and ecology of individual species, there is still a gap in research on direct, trophic interactions among extremophiles. To fill this gap, we experimentally studied the trophic interactions between a predatory protist (Actinophrys sol, Heliozoa) and its prey, the rotifers Elosa woralli and Cephalodella sp., the ciliate Urosomoida sp. and the mixotrophic protist Chlamydomonas acidophila (a green phytoflagellate, Chlorophyta). We found substantial predation pressure on all animal prey. High densities of Chlamydomonas acidophila reduced the predation impact on the rotifers by interfering with the feeding behaviour of A. sol. These trophic relations represent a natural case of intraguild predation, with Chlamydomonas acidophila being the common prey and the rotifers/ciliate and A. sol being the intraguild prey and predator, respectively. We further studied this intraguild predation along a resource gradient using Cephalodella sp. as the intraguild prey. The interactions among the three species led to an increase in relative rotifer abundance with increasing resource (Chlamydomonas) densities. By applying a series of laboratory experiments, we revealed the complexity of trophic interactions within a natural extremophilic community.
1. The biovolume-specific carbon content, relative egg volume (a measure of per-offspring reproductive investment), growth and grazing rates, and the gross growth efficiency (GGE) of the rotifer Cephalodella hoodi, isolated from an extremely acidic habitat (pH 2.65), were determined and compared with literature values for rotifers living in circum-neutral habitats in order to reveal potential special features or adaptations related to the extreme habitat of C. hoodi. 2. Of the two dominant phytoflagellates (Ochromonas sp. and Chlamydomonas acidophila) that occur in the natural habitat of C. hoodi, only C. acidophila promoted positive growth and reproduction and, thus, the following results were obtained with C. acidophila as a food alga. 3. The body volume-specific carbon content of C. hoodi is in the range of that found in rotifers from circum-neutral lakes, suggesting that no costly carbon investment, brought about by the thickening of the lorica, for example, was required to withstand low pH. 4. The egg volume of C. hoodi exhibited no phenotypic plasticity dependent on the food concentration and, thus, C. hoodi allocated a constant, absolute amount of energy to each individual offspring. No adaptation to low food densities was found. 5. A dome-shaped type II functional response curve was found to describe the ingestion of Chlamydomonas as a source of food. 6. Compared with other rotifers, C. hoodi had a high threshold and half-saturating food concentration (=low affinity) but also a high maximum growth rate and a relatively high GGE, suggesting no severe adverse effect of low pH
Herbivore populations are commonly restricted by resource limitation, by predation or a combination of the two. Food supplement experiments are suitable for investigating the extent of food limitation at any given time. The main part of this study was performed in an extremely acidic lake (pH 2.7) where the food web consists of only a few components and potential food sources for herbivores are restricted to two flagellates. Life table experiments proved that Chlamydomonas was a suitable food source whereas Ochromonas was an unsuitable food source. The two flagellates and the two rotifers exhibit a pronounced vertical distribution pattern. In this study, a series of food supplement experiments were performed in order to: (1) quantify and compare potential resource limitation of two primary consumers (Cephalodella hoodi and Elosa worallii, Rotatoria) over time, (2) compare their response at different temperatures, (3) evaluate the effect of having an unsuitable food source alongside a valuable one, (4) estimate the effect of predation on rotifers by Heliozoa, and (5) compare the results with those from other acidic lakes. Additionally, the spatio- temporal population dynamics of both species were observed. The field data confirmed a vertical separation of the two species with E. worallii dominating in the upper water layers, and C. hoodi in the deeper, cooler water layers. The results from the food supplement experiments in which Chlamydomonas served as the supplemented suitable food source showed that the two rotifers were food limited in the epilimnion throughout the season to different extents, with Cephalodella being more severely food limited than Elosa. The experiments at different temperatures provided evidence that Elosa had a higher optimum temperature for growth than Cephalodella. When the unsuitable food algae Ochromonas was added alongside the suitable food source Chlamydomonas, C. hoodi was unaffected but E. worallii was negatively affected. Predation of Heliozoa on rotifers was observed but the total effect on the rotifer dynamics is probably low. The comparison with other lakes showed that resource limitation also occurred in one other lake, although to a lesser extent. Overall, the vertical separation of the two rotifers could be explained by both their differential extent of resource limitation and differential response to temperature.
1. This is a discussion of the applicability to the phytoplankton of the concepts of 'Plant Functional Types' (PFTs) and 'Functional Diversity' (FD), which originated in terrestrial plant ecology. 2. Functional traits driving the performance of phytoplankton species reflect important processes such as growth, sedimentation, grazing losses and nutrient acquisition. 3. This paper presents an objective, mathematical way of assigning PFTs and measuring FD. Ecologists can use this new approach to investigate general hypotheses (e.g. the intermediate disturbance hypothesis (IDH), the insurance hypothesis and synchronicity phenomena), since, for example, in its original formulation the IDH makes its predictions based on FD rather than species diversity.
We investigated the role of GPER as a potential tumor suppressor in triple-negative breast cancer cells MDA-MB-231 and MDA-MB-468 using cell cycle analysis and apoptosis assay. The constitutive activity of GPER was investigated.
GPER-specific activation with G-1 agonist inhibited breast cancer cell growth in concentration-dependent manner via induction of the cell cycle arrest in G2/M phase, enhanced phosphorylation of histone H3 and caspase-3-mediated apoptosis. Analysis of the methylation status of the GPER promoter in the triple-negative breast cancer cells and in tissues derived from breast cancer patients revealed that GPER amount is regulated by epigenetic mechanisms and GPER expression is inactivated by promoter methylation. Furthermore, GPER expression was induced by stress factors, such as radiation, and GPER amount inversely correlated with the p53 expression level.
Overall, our results establish the protective role in breast cancer tumorigenesis, and the cell surface expression of GPER makes it an excellent potential therapeutic target for triple-negative breast cancer.
We investigated the morphology, phylogeny of the 18S rDNA, and pH response of Oxytricha acidotolerans sp. nov. and Urosomoida sp. (Ciliophora, Hypotricha) isolated from two chemically similar acid mining lakes (pH similar to 2.6) located at Langau, Austria, and in Lusatia, Germany. Oxytricha acidotolerans sp. nov. from Langau has 18 frontal-ventral-transverse cirri but a very indistinct kinety 3 fragmentation so that the assignment to Oxytricha is uncertain. The somewhat smaller species from Lusatia has a highly variable cirral pattern and the dorsal kineties arranged in the Urosomoida pattern and is, therefore, preliminary designated as Urosomoida sp. The pH response was measured as ciliate growth rates in laboratory experiments at pH ranging from 2.5 to 7.0. Our hypothesis was that the shape of the pH reaction norm would not differ between these closely related (3% difference in their SSU rDNA) species. Results revealed a broad pH niche for O. acidotolerans, with growth rates peaking at moderately acidic conditions (pH 5.2). Cyst formation was positively and linearly related to pH. Urosomoida sp. was more sensitive to pH and did not survive at circumneutral pH. Accordingly, we reject our hypothesis that similar habitats would harbour ciliate species with virtually identical pH reaction norm.
Multiple environmental stressors confine the ecological niche of the rotifer Cephalodella acidophila
(2013)
1The planktonic food web in extremely acidic mining lakes is restricted to a few species that are either acidophilic or acidotolerant. Common metazoans inhabiting acidic mining lakes with a pH below 3 include rotifers in the genera Cephalodella and Elosa. 2The life history response of Cephalodella acidophila to three environmental key factors, pH (2, 3.5, 5.0 and 7.0), temperature (10, 17.5 and 25 degrees C) and food concentration (10000, 35000 and 50000algal cells per mL), was investigated in a full factorial design using life-table experiments. 3The effect of each of the three environmental variables investigated on the rotifer life cycle parameters (life span, fecundity and population growth rate) differed. C.acidophila is a stenoecious species with a pH optimum in the range 34 and a comparably high food threshold. Combining the laboratory results with field data, we conclude that C.acidophila is severely growth limited in its natural habitat. However, low pH alone is not harmful as long as temperatures are moderate to warm and food is abundant. 4The population of C.acidophila in the field is maintained mainly due to release from competitors and predators.