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Biology subjects

Peter, C.

Publications and source records attributed to Peter, C..

10 recordsLinked to original sources

Biogeochemical function of slicks in coastal surface waters of the Baltic Sea

The sea-surface microlayer (SML) is a crucial ocean-atmosphere interface involved in gas exchange and nutrient cycling. Slicks, i.e., viscous surface layers, common in coastal regions serve as microbial hotspots. We studied microbial abundance, surfactants, dissolved organic carbon (DOC), and net community production (NCP) of O2 in slick and non-slick SMLs and underlying water (ULW) in the coastal Baltic Sea. Slicks often showed higher surfactant levels compared to the ULW. Microbial respiration often exceeded production, resulting in net O2 consumption, although some ULW sites exhibited net O2 production. The SML was enriched with pico- and nanophytoplankton, with cyanobacteria being negatively correlated with total dissolved nitrogen. In contrast, microphytoplankton accumulated in the ULW, indicating niche separation with depth. Microscopy revealed ciliates and juvenile sporophytes dominating a slicks >100 {micro}m fraction. In eutrophic coastal systems, slicks influence plankton communities and O2 dynamics, supporting their role in surface biogeochemical cycling and climate-driven changes.

microbiology↗

The role of secondary pollinators in the evolution of complex colour signals in a bimodal pollination system

Flower colour is recognized as a key trait influencing pollinator visitation and behaviour, evolved to match the sensory system of a particular pollinator group. However, some flowers combine colours associated with different pollinators, suggesting bimodal adaptation. The perennial herb Cyrtanthus obliquus produces red corollas with yellow tips and is pollinated by birds, but also by bees. To assess the role of the two pollinator categories in shaping selection on the bi-coloured corollas, we examined bee choices in arrays in which the colour signals of plants had been manipulated, and we quantified total as well as bird-mediated phenotypic selection on flower colour using both bird and bee visual models. Bees preferred flowers with a yellow signal over all-red flowers. The analysis of phenotypic selection indicated that both birds and bees influence net selection on flower colour, resulting in conflicting selection on the colour contrast between corolla and corolla tip. Our findings show that the optimal phenotype should depend on the relative importance of the two categories of pollinators in a given population, and are consistent with bimodal adaptation. This study fills an important gap by showing that secondary pollinators can contribute to selection on complex colour signals in angiosperm flowers.

evolutionary biology↗

Cryo-EM of soft-landed β-galactosidase: Gas-phase and native structures are remarkably similar

Native mass spectrometry (native MS) is a powerful technique that provides information on stoichiometry, interactions, homogeneity and shape of protein complexes. However, the extent of deviation between protein structures in the mass spectrometer and in solution remains a matter of debate. Here, we uncover the gas-phase structure of {beta}-galactosidase using single particle electron cryomicroscopy (cryo-EM) down to 2.6 [A] resolution, enabled by soft-landing of mass-selected protein complexes onto cold TEM grids and in-situ ice coating. We find that large parts of the secondary and tertiary structure are retained from solution, with dehydration-driven subunit reorientation leading to consistent compaction in the gas phase. Our work enables visualizing the structure of gas-phase protein com-plexes from numerous experimental scenarios at side-chain resolution and demonstrates the possibility of more controlled cryo-EM sample preparation. One Sentence SummaryElectrospray ion-beam deposition on cold grids and in-vacuum ice growth enable cryo-EM of mass-selected proteins at 2.6 [A].

biochemistry↗

"Wissenschaft fürs Wohnzimmer" - two years of interactive, scientific livestreams weekly on YouTube

Science communication is becoming increasingly important to connect academia and society, and to counteract fake news among climate change deniers. Online video platforms, such as YouTube, offer great potential for low-threshold communication of scientific knowledge to the general public. In April 2020 a diverse group of researchers from the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research launched the YouTube channel "Wissenschaft furs Wohnzimmer" (translated to "Sitting Room Science") to stream scientific talks about climate change and biodiversity every Thursday evening. Here we report on the numbers and diversity of content, viewers, and presenters from 2 years and 100 episodes of weekly livestreams. Presented topics encompass all areas of polar research, social issues related to climate change, and new technologies to deal with the changing world and climate ahead. We show that constant engagement by a group of co-hosts, and presenters from all topics, career stages, and genders enable a continuous growth of views and subscriptions, i.e. impact. After 783 days the channel gained 30,251 views and 828 subscribers and hosted well-known scientists while enabling especially early career researchers to improve their outreach and media skills. We show that interactive and science-related videos, both live and on-demand, within a pleasant atmosphere, can be produced voluntarily while maintaining high quality. We further discuss challenges and possible improvements for the future. Our experiences may help other researchers to conduct meaningful scientific outreach and to push borders of existing formats with the overall aim of developing a better understanding of climate change and our planet.

scientific communication and education↗

Combining molecular dynamics simulations and scoring method to computationally model ubiquitylated linker histones in chromatosomes

The chromatin in eukaryotic cells plays a fundamental role in all processes during a cells life cycle. This nucleoprotein is normally tightly packed but needs to be unpacked for expression and division. The linker histones are critical for such packaging processes and while most experimental and simulation works recognize their crucial importance, the focus is nearly always set on the nucleosome as the basic chromatin building block. Linker histones can undergo several modifications, but only few studies on their ubiquitylation have been conducted. Mono-ubiquitylated linker histones (HUb), while poorly understood, are expected to influence DNA compaction. The size of ubiquitin and the globular domain of the linker histone are comparable and one would expect an increased disorder upon ubiquitylation of the linker histone. However, the formation of higher order chromatin is not hindered and ubiquitylation of the linker histone may even promote gene expression. Structural data on chromatosomes is rare and HUb has never been modeled in a chromatosome so far. Descriptions of the chromatin complex with HUb would greatly benefit from computational structural data. In this study we generate molecular dynamics simulation data for six differently linked HUb variants with the help of a sampling scheme tailored to drive the exploration of phase space. We identify conformational sub-states of the six HUb variants using the sketch-map algorithm for dimensionality reduction and iterative HDBSCAN for clustering on the excessively sampled, shallow free energy landscapes. We present a highly efficient geometric scoring method to identify sub-states of HUb that fit into the nucleosome. We predict HUb conformations inside a nucleosome using on-dyad and off-dyad chromatosome structures as reference and show that unbiased simulations of HUb produce significantly more fitting than non-fitting HUb conformations. A tetranucleosome array is used to show that ubiquitylation can even occur in chromatin without too much steric clashes. Author summaryIn eukaryotic cells the linker histones play a crucial role in the formation of higher order nucleoprotein complex of DNA, especially for the arrangement of the nucleosomes. Histones can undergo several modifications, but modification of a linker histone with a single udiquitin (mono-ubiquitylation) remains one of the least understood epigenetic modifications. One reason is the inaccessibility of homogeneously modified linker histones for experimental methods, which are crucial for distinct studies. We combine molecular dynamics simulations with machine learning-based approaches to study the influence of mono-ubiquitylation in linker histones on DNA interaction and their ability to form higher order chromatin structures. We were able to determine the probable states in six differently linked histone-ubiquitin complexes via accelerating classical molecular dynamics simulations and using advanced state characterization techniques. As it is computationally unfeasible to simulate the whole chromatosome with different modified histones we developed efficient geometric scoring technique to select biologically relevant structures of all six mono-ubiquitylated linker histone that can bound to nucleosome.

bioinformatics↗

THEM6-mediated lipid remodelling sustains stress resistance in cancer

Despite the clinical benefit of androgen-deprivation therapy (ADT), the majority of patients with advanced prostate cancer (PCa) ultimately develop lethal castration-resistant prostate cancer (CRPC). In this study, we identified thioesterase superfamily member 6 (THEM6) as a marker of ADT resistance in PCa. In patients, THEM6 expression correlates with progressive disease and is associated with poor survival. THEM6 deletion reduces in vivo tumour growth and restores castration sensitivity in orthograft models of CRPC. Mechanistically, THEM6 is located at the endoplasmic reticulum (ER) membrane and controls lipid homeostasis by regulating intracellular levels of ether lipids. Consequently, THEM6 loss in CRPC cells significantly alters ER function, reducing de novo sterol biosynthesis and preventing lipid-mediated induction of ATF4. Finally, we show that THEM6 is required for the establishment of the MYC-induced stress response. Thus, similar to PCa, THEM6 loss significantly impairs tumorigenesis in the MYC-dependent subtype of triple negative breast cancer. Altogether, our results highlight THEM6 as a novel component of the treatment-induced stress response and a promising target for the treatment of CRPC and MYC-driven cancer.

cancer biology↗

The landscape of human brain immune response in patients with severe COVID-19

In coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, the relationship between brain tropism, neuroinflammation and host immune response has not been well characterized. We analyzed 68,557 single-nucleus transcriptomes from three brain regions (dorsolateral prefrontal cortex, medulla oblongata and choroid plexus) and identified an increased proportion of stromal cells and monocytes in the choroid plexus of COVID-19 patients. Differential gene expression, pseudo-temporal trajectory and gene regulatory network analyses revealed microglial transcriptome perturbations, mediating a range of biological processes, including cellular activation, mobility and phagocytosis. Quantification of viral spike S1 protein and SARS-CoV-2 transcripts did not support the notion of brain tropism. Overall, our findings suggest extensive neuroinflammation in patients with acute COVID-19. One Sentence SummarySingle-nucleus transcriptome analysis suggests extensive neuroinflammation in human brain tissue of patients with acute coronavirus disease 2019.

neuroscience↗

Common genetic variation in humans impacts in vitro susceptibility to SARS-CoV-2 infection

The host response to SARS-CoV-2, the etiologic agent of the COVID-19 pandemic, demonstrates significant inter-individual variability. In addition to showing more disease in males, the elderly, and individuals with underlying co-morbidities, SARS-CoV-2 can seemingly render healthy individuals with profound clinical complications. We hypothesize that, in addition to viral load and host antibody repertoire, host genetic variants also impact vulnerability to infection. Here we apply human induced pluripotent stem cell (hiPSC)-based models and CRISPR-engineering to explore the host genetics of SARS-CoV-2. We demonstrate that a single nucleotide polymorphism (rs4702), common in the population at large, and located in the 3UTR of the protease FURIN, impacts alveolar and neuron infection by SARS-CoV-2 in vitro. Thus, we provide a proof-of-principle finding that common genetic variation can impact viral infection, and thus contribute to clinical heterogeneity in SARS-CoV-2. Ongoing genetic studies will help to better identify high-risk individuals, predict clinical complications, and facilitate the discovery of drugs that might treat disease.

cell biology↗

Electroactive biofilms on surface functionalized anodes: the anode respiring behavior of a novel electroactive bacterium, Desulfuromonas acetexigens

Surface chemistry is known to influence the formation, composition and electroactivity of electron-conducting biofilms with however limited information on the variation of microbial composition and electrochemical response during biofilm development to date. Here we present voltammetric, microscopic and microbial community analysis of biofilms formed under fixed applied potential for modified graphite electrodes during early (90 h) and mature (340 h) growth phases. Electrodes modified to introduce hydrophilic groups (-NH2, -COOH and -OH) enhance early-stage biofilm formation compared to unmodified or electrodes modified with hydrophobic groups (-C2H5). In addition, early-stage films formed on hydrophilic electrodes were dominated by the gram-negative sulfur-reducing bacterium Desulfuromonas acetexigens while Geobacter sp. dominated on -C2H5 and unmodified electrodes. As biofilms mature, current generation becomes similar, and D. acetexigens dominates in all biofilms irrespective of surface chemistry. Electrochemistry of pure culture D. acetexigens biofilms reveal that this microbe is capable of forming electroactive biofilms producing considerable current density of > 9 A/m2 in a short period of potential induced growth (~19 h followed by inoculation) using acetate as an electron donor. The inability of D. acetexigens biofilms to use H2 as a sole source electron donor for current generation shows promise for maximizing H2 recovery in single-chambered microbial electrolysis cell systems treating wastewaters. HighlightsO_LIAnode surface chemistry affects the early stage biofilm formation. C_LIO_LIHydrophilic anode surfaces promote rapid start-up of current generation. C_LIO_LICertain functionalized anode surfaces enriched the Desulfuromonas acetexigens. C_LIO_LID. acetexigens is a novel electroactive bacteria. C_LIO_LID. acetexigens biofilms can produce high current density in a short period of potential induced growth C_LIO_LID. acetexigens has the ability to maximize the H2 recovery in MEC. C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/974261v1_ufig1.gif" ALT="Figure 1"> View larger version (55K): org.highwire.dtl.DTLVardef@1a9c7a5org.highwire.dtl.DTLVardef@1722697org.highwire.dtl.DTLVardef@143b996org.highwire.dtl.DTLVardef@14d4a60_HPS_FORMAT_FIGEXP M_FIG TOC - Graphical abstract C_FIG

bioengineering↗

Cholera in Internally Displaced Persons Camps in Borno State--Nigeria, 2017: A qualitative study of the multi-sectorial emergency response to stop the spread of the outbreak

Introduction/BackgroundIn August 2017, a cholera outbreak started in Muna Garage IDPs camp, Borno State-Nigeria, and >5000 cases occurred in six local government areas. This qualitative study evaluated perspectives about the emergency response to this outbreak.\n\nMethods/FindingsWe conducted 39 key informant interviews and focused group discussions, and reviewed 21 documents with participants involved with surveillance, water-sanitation-hygiene, case management, oral cholera vaccine, communications, logistics, and coordination. Qualitative data analysis used thematic techniques comprising key-words-in-context, word-repetition, and key-sector-terms.\n\nAuthorities were alerted quickly, but outbreak declaration took 12 days due to a 10 day delay waiting for culture confirmation. Outbreak investigation revealed several potential transmission channels, but a leaking latrine around the index cases house was not repaired for >7 days.\n\nUse of chlorine disinfectant was initially not accepted by the community due to rumors that it would sterilize women. This could have been avoided with improved community consultation. Initially, key messages were communicated in Hausa, although Kanuri was the primary language; later this was corrected. Planning would have benefited using exercise drills to identify weaknesses, and inventory sharing to avoid stock outs.\n\nThe response by the Rural Water Supply and Sanitation Agency was perceived to be slow and an increased risk from Eid El Jabir festival with increased movement and food sharing was not recognized. Case management was provided at treatment centers, but some partners were concerned that their work was recognized asking, \"who gets the glory and the data?\"\n\nOCV was provided to nearly one million people and it distribution benefited from a robust polio vaccine structure; however, logistical problems related to payment of staff needed resolution.\n\nInitial coordination was thought to be slow, but improved by activating an Emergency Operations Centre. The Borno Ministry of Health used an Incident Management System to coordinate multi-sectoral response activities.\n\nThese were informed by daily reviews of epi curves and geo-coordinate maps. The synergy between partners and government improved when each recognized the governments leadership role.\n\nConclusions/SignificanceDespite a timely alert of the outbreak, the delayed declaration led to a slowed initial response, but this improved during the course of the outbreak. OCV distribution was efficient and benefited from the OPV infrastructure. Improvements in laboratory capacity are urgently needed.\n\nAuthor SummaryIn August 2017, a cholera outbreak started in the Muna Garage Internally Displaced Persons (IPDs) camp in Borno State, Nigeria. By October, it appeared in six local government areas with a total of 5,340 cases reported including 61 deaths. We evaluated the perspectives of the emergency response by the government of Nigeria and implementing partners to stop the outbreak. We conducted 39 interviews and group discussions and also studied 21 documents related to the outbreak response. We found that epidemiologic surveillance timely alerted the health authorities about the outbreak, but the outbreak was declared 12 days later, awaiting for culture confirmation. This led to delays in the initial response. We also observed that conditions in the IDPs camps like overflowing latrines, overcrowding, and open defecation were highly favorable to cholera transmission. Improved IDP camp conditions are needed to prevent cholera and other water born infections and strengthened laboratory capacity is needed to enable a more rapid response.

epidemiology↗