Biology subjects

Schlegel, M.

Publications and source records attributed to Schlegel, M..

8 recordsLinked to original sources

bioRxiv2025

Physiological diversity and adaptation of Rhizaria revealed by phylogenomics and comparative transcriptomics

Protists are vastly diverse, forming over 20 supergroups of the eukaryotic diversity and fulfilling plentiful functions. Rhizaria is a widespread and highly abundant supergroup comprising important parasites and a huge diversity of free-living heterotrophic predators. Despite the diversity and biogeochemical importance of Rhizaria, our understanding of their physiology and metabolic capabilities remains limited, mainly due to a general lack of data and bioinformatic tools for cross-species comparisons of physiological traits. In this study, we assembled a total of 15 transcriptomes of the parasite-related bacterivorous Rhogostoma and their eukaryvorous relatives. By phylogenomic analyses and whole transcriptome comparison, we established an evolutionary framework to which we relate physiological traits. The morphologically highly similar Rhogostoma strains branch in two distinct clusters differing in orthogroups and gene expression patterns related to cell adhesion and biofilm formation. Furthermore, we reveal considerable intra-genus variation in amino acid and lipid metabolism, which might be explained by an ancient streamlining through gradual specialization to parasitism, bearing the potential for subsequent metabolic radiation. We conclude that even closely related and morphologically similar species in Rhizaria may differ distinctly in their functional repertoire. With the here established and showcased analyses, we create a basis for future characterization of the physiological traits of microeukaryotes.

microbiology↗

bioRxiv2025

Fabry-Perot Microscopy for Improved Contrast Enhancement and 3D Cellular Imaging

Fabry-Perot Microscopy (FPM) integrates a lab-on-a-chip optical cavity and tunable light source in a label-free imaging technique that enhances contrast and enables pseudo-three-dimensional imaging in transparent biological samples. By integrating a fixed-length Fabry-Perot cavity into a coated microfluidic cell, FPM selectively highlights structures of defined optical thickness through resonance-based interference. We demonstrate that this architecture preserves lateral resolution while providing up to 20-fold contrast enhancement compared to conventional wide-field microscopy. Using human epithelial cells, blood components, and E. coli bacteria, we show that FPM enables clear visualization of subcellular features and discrimination of cell types. Spectrally resolved image stacks are used to extract pixel-wise optical thickness maps, from which physical thickness and refractive index can be derived. These parameters reveal nanoscale structural differences and offer routes to biophysical characterization. Notably, the system operates without mechanical scanning the cavity, using spectral tuning alone to generate images. FPM is compatible with standard microscope optics, and functions under static or flow-compatible conditions, making it suitable for high-throughput cytometry and in vitro diagnostics. These results establish FPM as a versatile extension to wide-field microscopy, enabling contrast-tunable, quantitative imaging of biomedical specimen.

biophysics↗

bioRxiv2025

A novel protistan trait database reveals functional redundancy and complementarity in terrestrial protists (Amoebozoa & Rhizaria)

The inclusion of functional traits of protists in environmental sequencing surveys, in addition to the traditional taxonomic framework, is essential for a better understanding of their roles and impacts on ecosystem processes. We provide a database of functional traits for a widespread and important clade of protists, the Amoebozoa, based on extensive literature research in eight trait categories: Habitat, locomotion, nutrition, morphology, morphotype, size, spore formation, and disease-relatedness. The comparison of community traits of the Amoebozoa with sympatric but highly divergent Cercozoa (Rhizaria) revealed both convergent evolution of morphology or locomotion and distinct differences in habitat preference and feeding selectively. Amoebozoa seem to be rather unselective in their prey choice compared to Cercozoa. Indeed, the feeding preferences of Amoebozoa appeared to be related to cell size, whereas Cercozoa selectively feed on prey. Applications to metatranscriptomic data from soil, litter, and bark surfaces revealed differences in the average community trait compositions and ecosystem functioning, such as an increased proportion of disease-related Amoebozoa in soil or different proportions of nutrition types of Amoebozoa and Cercozoa on bark. This database will facilitate ecological analyses of sequencing data and improve our understanding of the diversity of adaptations of Amoebozoa to the environment and their functional roles in ecosystems.

ecology↗

bioRxiv2023

Chronic administration of XBD173 ameliorates cognitive deficits and neuropathology via 18 kDa translocator protein (TSPO) in a mouse model of Alzheimer disease

Alzheimers disease (AD) is characterized by the accumulation of {beta}-amyloid peptide (A{beta}). There is increasing evidence that depression may precede AD and may be an early manifestation of dementia, suggesting common mechanisms underlying both diseases. Ligands targeting the mitochondrial translocator protein (18 kDa) (TSPO), promote neurosteroidogenesis and may be neuroprotective. Moreover, TSPO is upregulated in AD. To study whether the TSPO ligand XBD173 may exert early neuroprotective effects in AD pathology we investigated the impact of XBD173 on amyloid toxicity and neuroplasticity in mouse models. We show that XBD173 (emapunil), via neurosteroid-mediated signaling via delta subunit-containing GABAA receptors, prevents the neurotoxic effect of A{beta} on long-term potentiation (CA1-LTP) in the hippocampus and prevents the loss of spines. Chronic but not acute administration of XBD173 ameliorates spatial learning deficits in transgenic AD mice with arctic mutation (ArcA{beta}) mice. The heterozygous TSPO-knockout crossed with the transgenic arctic mutation model of AD mice (het TSPOKO X ArcA{beta}) treated with XBD173 does not show this improvement in spatial learning suggesting TSPO is needed for procognitive effects of XBD173. The neuroprotective profile of XBD173 in AD pathology is further supported by a reduction in plaques and soluble A{beta} levels in the cortex, increased synthesis of neurosteroids, rescued spine density, reduction of complement protein C1q deposits, and reduced astrocytic phagocytosis of functional synapses both in the hippocampus and cortex. Our findings suggest that XBD173 may exert therapeutic effects via TSPO in a mouse model of AD.

neuroscience↗

bioRxiv2021

A parasite's paradise: Biotrophic species prevail oomycete community composition in tree canopies

Oomycetes (Stramenopiles, Protista) are among the most severe plant pathogens, comprising species with a high economic and ecologic impact on forest ecosystems. Their diversity and community structures are well studied in terrestrial habitats, but tree canopies as huge and diverse habitats have been widely neglected. A recent study highlighted distinct oomycete communities in the canopy region compared to forest soils when taking oomycete abundances into account, in contrast to the homogeneity at the incidence level. It remains however unknown if this homogeneity also leads to a functional homogenisation among microhabitats. In this study, we supplemented functional traits to oomycete canopy and ground communities, which were determined over a time period of two years with a metabarcoding approach. Our results showed that even though most oomycetes occurred in all habitats, a strong discrepancy between the strata and correspondingly the distribution of oomycete lifestyles could be observed, which was constant over time. Obligate biotrophic species, exclusively feeding on living host tissue, dominated the canopy region, implying tree canopies to be a hitherto neglected reservoir for parasitic protists. Parasites highly specialised on hosts that were not sampled could be determined in high abundances in the canopy and the surrounding air, challenging the strict host dependencies ruled for some oomycetes. Our findings further contribute to the understanding of oomycete ecosystem functioning in forest ecosystems.

microbiology↗

bioRxiv2021

On the phenology of protists: Recurrent patterns reveal seasonal variation of protistan (Rhizaria: Cercozoa, Endomyxa) communities in tree canopies

Tree canopies are colonized by billions of highly specialized microorganisms that are well adapted to the extreme microclimatic conditions, caused by diurnal fluctuations and seasonal changes. In this study we investigated seasonality patterns of protists in tree canopies of a temperate floodplain forest via high-throughput sequencing with group-specific primers for the phyla Cercozoa and Endomyxa. We observed consistent seasonality and identified divergent spring and autumn taxa. Tree crowns were characterized by a dominance of bacterivores and omnivores, while eukaryvores gained a distinctly larger share in litter and soil communities on the ground. Seasonality was largest among communities detected on the foliar surface. Higher variance within alpha diversity of foliar communities in spring indicated greater heterogeneity during community assembly. However, communities underwent distinct changes during the aging of leaves in autumn, reflecting recurring phenological changes during microbial colonization of leaves. Surprisingly, endomyxan root pathogens appeared to be exceptionally abundant across tree canopies during autumn season, demonstrating a potential role of the canopy surface as an important reservoir for wind-dispersed propagules. Overall, about 80% of detected OTUs could not be assigned to known species - representing only a fraction of dozens of microeukaryotic taxa whose canopy inhabitants are waiting to be discovered.

ecology↗

bioRxiv2020

To the canopy and beyond: Air samples reveal wind dispersal as a driver of ubiquitous protistan pathogen assembly in tree canopies

We analyzed air dispersal of the protistan phyla Cercozoa and Oomycota with an air sampler near the ground (~2 m) and in tree crowns (~25 m) of three tree species (oak, linden and ash) in a temperate floodplain forest in March (before leafing) and May (after leaf unfolding) with a cultivation-independent high throughput metabarcoding approach. Both, Cercozoa and Oomycota, contain important pathogens of forest trees and other vegetation. We found a high diversity of Cercozoa and Oomycota in air samples with 122 and 81 OTUs, respectively. Especially oomycetes showed a high temporal variation in beta diversity between both sampling dates. Differences in community composition between air samples in tree canopies and close to the ground were however negligible, and also tree species identity did not affect communities in air samples, indicating that the distribution of protistan propagules through the air was not spatially restricted in the forest ecosystem. OTUs of plant pathogens, whose host species that did not occur in the forest, demonstrate wind dispersal of propagules from outside the forest biome. Overall, our results lead to a better understanding of the stochastic processes of wind dispersal of protists and protistan pathogens, a prerequisite to understand the mechanisms of their community assembly in forest ecosystems. ImportanceWind dispersal has been shown to play a crucial role in protistan community assembly. The protistan taxa Cercozoa and Oomycota contain important plant parasites with a major ecologic and economic impact. However, comprehensive assessments of cercozoan and oomycete diversity in forest air samples were lacking. Using a cultivation-independent high throughput metabarcoding approach, we analyzed cercozoan and oomycete air dispersal in forest floors and the canopy region - a potential filter for microbial propagules. Our study provides insights into the diversity and community assembly of protists within the air, contributing to a better understanding which factors drive the distribution of plant pathogens within forest ecosystems.

ecology↗

bioRxiv2018

Infections patterns and fitness effects of Rickettsia and Sodalis symbionts in the green lacewing Chrysoperla carnea

Endosymbionts are wide-spread among insects and can play an essential role in host ecology. The common green lacewing (Chrysoperla carnea s. str.) is a neuropteran insect species which is widely used as a biological pest control. We screened for endosymbionts in natural and laboratory populations of the green lacewing using diagnostic PCR amplicons. We found the endosymbiont Rickettsia to be very common in all screened populations, whereas a so far uncharacterized Sodalis strain was solely found in laboratory populations. The new Sodalis strain was characterized using a whole genome shotgun approach. Its draft genome revealed an approximate genome size of 4.3 Mbp and the presence of 5213 coding sequences. Phylogenomic analyses indicated that this bacterium is the sister taxon of S. praecaptivus. In an experimental approach, we found a negative impact of Sodalis on the reproduction success of the green lacewing. Co-infections with Rickettsia and Sodalis caused an even higher decrease of reproductive success than single Sodalis infections. In contrast, no significant fitness differences were found in Rickettsia infected green lacewings compared to uninfected lacewings. The Rickettsia/Sodalis/Ch. carnea system presents a promising model to study evolutionary endosymbiont-host interactions in Neuroptera and endosymbiont-endosymbiont interactions in general. The economic and ecological importance of green lacewings in biological pest control warrants a more profound understanding of its biology, which might be strongly influenced by symbionts.

evolutionary biology↗