Czechia

Biotic interaction with complex communities of microbiota inhabiting every mucosal surface of teleost fish strongly influence the host metabolism, growth and health. The gill mucosal surface constitutes a special habitat for host-associated microbes due to its unique functions in waste excretion, gas exchange and local immune activity. The gill associated lymphoid tissue (GIALT) enables fish to discriminate between beneficial and pathogenic bacteria keeping microbiome homeostasis. Changes in the environment however, including water conditions, seasonal changes and physiological stress can lead to compositional disturbances that turn commensals into pathogens. This sensitivity to environmental parameters provides the opportunity to use the microbiome composition of the external mucus as a biomarker for the health of the fish. 
Here we compare the microbial gill mucus communities of the two teleost species Osmerus eperlanus and Gymnocephalus cernua from different life-history guilds and the bacterioplankton in the Elbe estuary. Over the course of one year, we collected 220 fish along the main channel of the estuary and generated matching 16S rRNA metabarcoding and host transcriptome libraries. The aim is to characterize the physiological response along spatio-temporal gradients, extract bacterial indicator species and determine driving factors for fish health.


SEB Conference 2024

Wild fish holobiont response to abiotic gradients in the Elbe estuary

estuary

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SEB’s Annual Conference is celebrated for creating the perfect composition of research, new discoveries and collaborative connections. Be creative and innovative by exchanging ideas and knowledge with masters of biology from all over the world.

technical paper

In recent years, human activities in German waters have expanded continuously, impacting native harbour porpoise populations (Phocoena phocoena). Harbour porpoises often display severe pathological lesions in the respiratory tract, mainly caused by bacteria and parasites. Additionally, telemetry studies revealed they do not use their complete lung volume. It has not been studied whether this is due to the pathological lung lesions reducing the oxygen uptake of the porpoises, impairing their diving ability. 
Using multi-omics, this study aims to investigate whether harbour porpoises developed compensatory molecular adaptations to an inadequate oxygen uptake, therefore staying competitive. 
Multi-omics of non-healthy harbour porpoise lungs revealed an enhanced response to reactive oxygen species such as hydrogen peroxide known to cause oxidative stress. Potent detoxifiers such as multiple S100A genes and glutathione peroxidases were upregulated and highly abundant. Also, an extensive activation of immune system responses against microbes, bacteria and other organisms was identified. Elevated chemotaxis hints at a swift aggregation to the site of infection or inflammation, while mucosal immune responses and transport suggests quick pathogen removal. Moreover, upregulation of surfactant proteins may aid in immunoprotection and respiration of the impaired lung tissue. Reduced cell adhesion, tissue remodelling and apoptosis execution may avoid further damage by suspending cell-cell interactions and cell death.
These insights suggest a comprehensive immune response to pathogens, inflammation and reaction to ROS, enabling specific functional analyses of newly identified transcripts. Further, this study illustrates the potential of multi-omics to noninvasively advance the knowledge of marine mammal adaptations, especially to anthropogenic impacts.

Integrative multi-omics approach reveals a possible adaptation of harbour porpoise lung tissue as response to damage

Climate warming is pushing aquaculture species to their physiological limits through elevated temperature pressures impacting feed intake, nutrient use, growth, health, and welfare. Emerging research shows that diet (and dietary supplements) can play a significant role in modulating the stress response and improving thermal tolerance, which is pivotal in aquaculture species as the oceans continue to warm. 5-aminolevulinic acid (5-ALA), is an emerging dietary supplement that is the sole precursor to heme and fundamental for the formation of hemoproteins involved in aerobic energy metabolism (haemoglobin, myoglobin, cytochrome c oxidase) and the antioxidant system (catalase). Using juvenile barramundi as a model species, a feed trial was conducted for 6 weeks utilising 5-ALA supplementation in aquafeeds at 3 inclusion levels (control (0 ppm), 15 ppm, 30 ppm). Water temperature was ramped up from 30°C to 37°C, over 4 weeks to determine the diet effects under chronic thermal stress conditions. Although haemoglobin levels and catalase activities remained similar among treatments, growth rates increased with 5-ALA supplementation. 5-ALA supplementation also increased mitochondrial respiration in Oxidative Phosphorylation (OXP) with substrates supporting Complexes I and II. However, oxygen flux in the Leak (non-phosphorylating) respiration state remained similar, indicating that the Leak/OXP ratio decreased with 5-ALA. Therefore, the capacity and apparent efficiency to synthesise ATP had increases with 5-ALA. Overall, as a dietary supplement 5-ALA holds promise in aquafeeds through increasing mitochondrial efficiency, which may account for the observed increases in growth rates, which can improve production efficiency during periods of environmental stress within the aquaculture industry.

Enhancing mitochondrial efficiency: small dietary changes improve fish growth under chronic thermal stress

While hypoxia (i.e. low dissolved oxygen level in water) events occur naturally, global change and human activities have exacerbated their strength and temporal fluctuations. As populations may not be able to escape the hypoxic conditions, it is crucial to understand how organisms can adjust and adapt to these fluctuating environments across generations. When directly exposed, individuals may be able to adjust their phenotypes through plasticity to maintain their fitness. With continued exposure to hypoxia over generations, adaptive transgenerational plasticity can take place to help the offspring to survive the new conditions. Even longer exposure could also lead to the evolution of the population. However, so far, little is known on how plastic response to hypoxia could actually pave the way for future evolution. Using two populations of three-spined sticklebacks (Gasterosteus aculeatus) collected from streams already experiencing and potentially adapted to strong hypoxic events or not, we exposed the offspring to experimental hypoxia (30% air saturation during the night and 100% during the day) over three generations, resulting in several groups reflecting within-, inter-, and trans-generational plasticity, as well as adaptation. We then measured their growth, metabolism, and behaviour and highlighted that the plastic responses observed were not necessarily in line to the potential adaptation. While the directions of the responses were different, we cannot exclude that the fish plasticity might still be a strategy to cope with the environment until genetic adaptation occur.

Fish cross-generational response to hypoxia: can plasticity pave the way to evolution?

This study aims to bridge the gap between the physiological response of Polar cod, Boreogadus saida, to ocean acidification and global warming, and the underlying molecular mechanisms. In this comprehensive project, a variety of physiological parameters (e.g.: growth and exercise) were investigated in response to ocean warming and acidification. The fish were long-term acclimated to three different CO2 concentrations: 390 ppm, a moderate increase (780 ppm), and high PCO2 levels corresponding to the business-as-usual greenhouse gas emission scenario (RCP8.5, 1170 ppm). Each CO2 treatment was combined with four temperatures, 0, 3, 6, 8°C to simulate different warming scenarios. In this study, we focused on the transcriptomic profiles from liver of these incubated and physiologically tested fish to identify critical molecular mechanisms underlying the previous reported physiological responses. Generally, we did not detect signs of a classical stress response, even at the highest temperature after four months of exposure. Consistent with previous observations, the molecular responses to ocean acidification were minor compared to temperature, but an interaction between both factors existed at least for some metabolic processes. Gene ontology analysis revealed a strong response in lipid-, carbohydrate- and protein metabolism. With increasing temperature, we observed a shift away from lipid metabolism, while carbohydrate metabolic pathways remained stable. Although we found Polar cod to be highly resilient to ocean acidification, temperature will remain a critical parameter for this valuable Arctic keystone species and the question remains whether adaptation mechanisms can be implemented in its natural habitat, especially when food supply is limited.

Transcriptomic response of Polar cod, Boreogadus saida, to ocean acidification and warming

The remarkable mechanical properties of spider silk, especially its extensibility and strength, have long fascinated naturalists and engineers alike. Recent advancements have focused on unravelling the structural hierarchies and biochemical compositions that confer these unique properties, paving the way for biomimetic applications in materials science and engineering. In this scenario, spider capture threads pose a unique challenge, as many spiders produce metastructures, which unknown properties depend on both the mechanical characteristics of the fibres composing them, and their geometrical arrangement.
In this work, we focused on the biomechanics of the capture threads of the Southern house spider (Kukulcania hibernalis) employing a combination of high-resolution tensile testing, microscopic examinations, and theoretical modelling. Our findings reveal the critical role of the hidden lengths provided by a unique hierarchical looped fibre architecture, which enhance the thread’s extensibility. Thanks to the theoretical modelling, we reveal how the outstanding extensibility observed in the capture threads of Kukulcania can be explained independent of the nano-structure of the fibres. Furthermore, our research highlights the potential of spider silk meta-structures as a model system for developing fibre-based materials that mimic biological structures for enhanced mechanical performance.


Extreme elongations of Kukulcania hibernalis threads thanks to looped meta-structures

Repeated hypoxic events are reported in various brain pathologies. Mammal brain is highly vulnerable to hypoxia, because brain functions require high oxygen and energy demands. Marine mammals, such as pinnipeds, were naturally selected to cope with daily repeated hypoxic events during foraging dives, when human brain can only cope with minor repeated hypoxia. How do pinnipeds cope with repeated severe hypoxic events at the blood-brain interface? We performed a comparative physiological approach using for model the Southern Elephant Seal (SES), which is the most extreme diver of all seals and being exposed to severe peripheral hypoxia.
Immunolabelling of various blood-brain interface markers (endothelium, astrocytes, neurons) were performed on brain cortical slices from freshly dead post-weaning pups (n=4) and reproductive adults (n=5) collected at Kerguelen Island. Immunolabelling were visualised using confocal microscope and images were analysed using ImageJ. 
Cerebral vascularisation exhibits significant differences between pups and adults: 1) in the grey matter, the vascular volume fraction was around 62% higher in adults than in pups; 2) the vessels were significantly more ramified and tortuous in adults (e.g. 6% more tortuous in the white matter); 3) some large blood vessels exhibited abnormalities in adults suggesting blood-brain interface dysfunctions. Interestingly, adult SES vessels share similar phenotypes to pathological cerebral-blood vessels described in human neurodegenerative diseases. Then, abnormal vessel-morphologies raise the question of the potential pathological situation for adult SES. To study blood-flow velocity in brain-vessels and premature aging in SES, biomechanical fluid modelling, additional staining for neurodegenerative landmarks and blood-biomarkers are currently performed.

Does cerebral blood vessel phenotype represent and adaptative response to repeated hypoxia in the southern elephant seal?

Male tree crickets produce advertisememt calls that are essential for mating success. Perception of this sound involves the capture of sound waves by an eardrum and mechanoreception of vibrations by sensory cells within the ear. To aid the detection of courtship calls present at low levels in noisy environments, tree crickets use active amplification within the ear. However, this sensitive system may be overwhelmed when noise is loud or similar in frequency to the call of interest. In this study, we performed a series of experiments to determine how and whether a tree cricket Oecanthus nigricornis eardrum is able to represent a call of interest in the presence of a simulated chorus of distracting calls at varying sound pressure levels and frequencies. Because anthropogenic noise has also been shown to impact the ability for many animals to acoustically communicate, we also performed experiments with white and pink noise as a distracting signal to simulate noise regimes generated by humans. This work provides insight on the mechanical functioning of cricket ears, and also on how these animals may be affected by different ecological conditions, including those generated by humans.

Tree cricket tympanal mechanics in noisy environments

The centromere is the chromosome region where the microtubules attach during cell division. In monocentric species, new centromeres can appear during evolution at an ectopic chromosomal location. A new centromere often tends to form near the progenitor centromer, and frequently, the establishment of a new centromere is accompanied by inactivation or loss of function of the old centromere. Initially, newly formed centromeres do not usually contain repeat DNAs but mature gradually through the acquisition and accumulation of repeats. As soon as one or a few repeats invade the novel centromere, their accumulation can be achieved by extended gene conversion during DSB repair. In addition to monocentric eukaryotes, which have a single localized centromere on each chromosome, there are holocentric species, with extended repeat-based or repeat-less centromeres distributed over the entire chromosome length. At least two types of repeat-based holocentromeres exist, one composed of many small repeat-based centromere units (small unit-type), and another one characterized by a few large centromere units (large unit-type). We hypothesize that the transposable element-mediated dispersal of hundreds of short satellite arrays and DNA repair formed the small centromere unit-type holocentromere in e.g. Rhynchospora pubera. The large centromere unit-type of the e.g. plant Chionographis japonica is likely a product of simultaneous DNA double-strand breaks and DNA repair, which initiated the de novo formation of repeat-based holocentromeres via insertion of satellite DNA, derived from extra-chromosomal circular DNAs (eccDNAs).

Centromere diversity - Does DNA repair drive the evolution of repeat-based holocentromeres?

Excellent research requires excellent leadership, but the goalposts for leadership excellence in life sciences are moving. Everyone regardless of seniority has leadership responsibility, and creating an accessible, inclusive, and responsive biology research environment that accurately reflects member's needs is vital for success across the sector. Despite this, it can be challenging to ensure everyone receives appropriate accommodations based on their needs. This co-created project uncovers the core tenets of inclusive leadership in biology, underlines the importance of intersectionality, and encourages participants to look beyond their own experiences and expectations of leadership. This talk explores the Inclusive Leadership Resource, shares pilot data from our self-scoring system, and highlights the importance of co-creation processes when modelling culture change in research environments. Ultimately, talk aims to equip participants with confidence, creativity, and deeper understanding when approaching intersectionality and accommodations in biological research environments.

Integrating Intersectionality: A New Lens on Leadership in Experimental Biology

Strigolactones (SLs) are a plant hormone known for inhibiting branching/tillering. Moreover, Plants release SLs into the soil to attract symbiotic mycorrhizal fungi. However, released SLs are also perceived as germination signal by seeds of root parasitic plants, such as Striga hermonthica. Structurally, natural SLs are diverse and divided into canonical and non-canonical SLs. One of the most intriguing questions in SL biology is whether all SLs fulfill the same functions as hormones in planta and simultaneously as rhizospheric signals. To address this question, we generated rice mutants lacking canonical SLs and showed that they do not exhibit the phenotypes characteristic for SL-deficient mutants, i.e. high-tillering and dwarfism. However, these mutants release exudates with a significantly reduced Striga seed-germinating activity, indicating a particular function of canonical SLs as rhizospheric signals. Furthermore, generating of rice mutants that accumulates 4-deoxyorobanchol revealed a particular function of this canonical SL as a negative regulator of shoot and panicle growth and a promoter of root growth. Taken together, our work inarguably identifies particular functions of different SL classes, opening up the possibility of targeted design of plant architecture and modulating rhizospheric communications.

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Integrative multi-omics approach reveals a possible adaptation of harbour porpoise lung tissue as response to damage

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Potential for gill-oxygen limitation in acute but not chronic thermal tolerance

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