Biology subjects

Carstensen, M.

Publications and source records attributed to Carstensen, M..

8 recordsLinked to original sources

bioRxiv2026

Soil nitrogen dynamics in riparian zones of two Arctic rivers

Riparian zones act as protective buffers, filtering land-to-river nutrient inputs through retention and nitrogen (N) gas losses. While rapid Arctic warming and permafrost thaw may enhance terrestrial nutrient inputs to aquatic systems, comprehensive assessments of N cycling in Arctic riparian soils are lacking. Conventionally, these zones are considered inactive due to N limitation of Arctic soils and low temperatures, leaving their N cycling unexplored. To address this, we investigated N pools and turnover processes in riparian zones of two Arctic rivers in Finland and Greenland. We combined measurements of the extractable N pool and in-situ nitrous oxide (N2O) flux with 15N-labeling techniques to quantify gross mineralization, nitrification, potential denitrification, and potential dissimilatory nitrate reduction to ammonium (DNRA). Our findings reveal that mineral N cycling in high-latitude riparian zones is more active than previously assumed. Despite low temperatures and low to intermediate soil organic carbon content, we found high gross N mineralization rates, alongside detectable rates of gross nitrification and potential DNRA. We attribute the unexpectedly high N activity in C-poor soils to low C/N ratios, which create a stoichiometric imbalance, thereby enhancing N mineralization. The presence or absence of vegetation largely determined the dominance and magnitude of these pathways. While dense vascular plant cover was associated with higher extractable N pools and gross mineralization rate, low nitrification rates and elevated DNRA potential indicated a tight N cycle. Conversely, sparsely vegetated patches with cryptogamic biocrusts acted as N2O hotspots. In bare sandy soils adjacent to the river, we found high gross nitrification rate and detectable N2O losses, possibly driven by riverine organic N inputs. Taken together, this research shows that Arctic riparian zones may play an important role in reducing terrestrial N inputs to the rivers, which should be considered when studying the fate of N in the rapidly changing Arctic.

ecology↗

bioRxiv2025

Environmental identification of novel enzymes against heteroatomic plastics

Better enzymes are needed to develop sustainable methods to recycle plastics with C-X heterobonds such as polyurethane (PUR) and nylon, for which no industrial-scale solutions exist. Current methods rely largely on sequence mining based on a small number of known enzymes. Here we expand the pool of PURases and nylonases by bioprospecting legacy plastic waste with fluorophore plastic mimics combined with FACS. We identify 29 plastic-degrading bacteria, from which 12 enzymes are identified by mass spectrometry and homology searches. Compared to existing enzymes, these enzymes are superior in thermostability and the ability to hydrolyse different high-molecular weight PUR oligomers and nylon textiles. To our knowledge, this is the first reported example of enzymes capable of hydrolysing longer chains of PUR and nylon. This study significantly increases the number of known PURases and nylonases and provides starting points for optimization campaigns through protein engineering and for in silico discovery.

biochemistry↗

bioRxiv2025

Using magnetoencephalography to track the propagation of 40 Hz invisible spectral flicker

Brain stimulation with novel 40 Hz invisible spectral flicker (ISF) has been proposed as a therapy for Alzheimers disease, with leading hypotheses suggesting local promotion of glymphatic clearance of amyloid as the mechanism of action. Neural signals in the gamma range and their spatial propagation over the brain can be tracked using magnetoencephalography (MEG) with high temporal and good spatial detail. However, stimulation with 40 Hz ISF requires specialised hardware which causes electromagnetic interference (EMI) with MEG equipment. MEG measures the tiny magnetic fields of the brain, which are easily distorted by external magnetic fields. Using MEG to track the propagation of 40 Hz ISF requires multiple modifications to the experimental setup. These include, at least 1) an experimental design that promotes modulation of the neural signal, but not the artifact, 2) removal of all electronics not strictly necessary for light production from the stimulators, and 3) signal processing for 40 Hz EMI artifact suppression. Here, we present an MEG study on the cortical propagation of 40 Hz ISF. In two experiments, we investigate the modulation that visual and non-visual cognitive tasks have on the power and propagation of cortical activity induced by 40 Hz ISF. With the chosen experimental setup and design, the 40 Hz EMI artifact could not be entirely disentangled from the neural signal of interest, thus rendering inference on the spatial propagation of the 40 Hz signal impossible. Further improvements need to be implemented in a follow-up experimental design. We present potential solutions to allow for future investigation of 40 Hz ISF with MEG.

neuroscience↗

bioRxiv2023

Defective Integrator activity shapes the transcriptome of patients with multiple sclerosis

HP1/CBX5 is an epigenetic regulator with a suspected role in multiple sclerosis (MS). Here, using high-depth RNA sequencing on monocytes, we identified a subset of MS patients with reduced CBX5 expression, correlating with progressive stages of the disease and extensive transcriptomic alterations. Examination of rare non-coding RNA species in these patients revealed impaired maturation/degradation of U snRNAs and enhancer-RNAs, indicative of a reduced activity of the Integrator, a complex with suspected links to increased MS risk. At protein-coding genes, compromised Integrator activity manifested in reduced pre-mRNA splicing efficiency and altered expression of genes regulated by RNA polymerase II pause-release. Inactivation of Cbx5 in the mouse mirrored most of these transcriptional defects and resulted in hypersensitivity to Experimental Autoimmune Encephalomyelitis (EAE). Collectively, our observations suggested a major contribution of the Integrator complex in safeguarding against transcriptional anomalies characteristic of MS, with HP1/CBX5 emerging as an unexpected regulator of this complexs activity. These findings bring novel insights into the transcriptional aspects of MS and provide potential new criteria in patient stratification.

genomics↗

bioRxiv2023

Unexpected contribution to the prevailing trend of positive results for 40 Hz light flicker

This comment addresses the potential influence of sample size on the conclusions drawn from a study investigating the beneficial effects of neuropathology in Alzheimers disease (AD). By examining the existing literature and employing statistical reasoning, we argue that an increase in sample size by factor of 2-4 would have led the authors to arrive at a different conclusion. Contrary to expectations, their findings unexpectedly contribute to the prevailing trend of positive results regarding the advantageous impacts of neuropathology in AD, with nine out of ten of their immunohistochemistry experiments showing a consistent [~]30 % reduction of amyloid plaque. We demonstrate that the quantity and quality of the data presented by Soula et al. 2023 do not support the papers conclusions on amyloid neuropathology. Based on a thorough statistical analysis of the available data, we therefore submit that given a larger sample size, the conclusion would have been positive towards possible improvements in neuropathology.

neuroscience↗

bioRxiv2021

RT-QuIC detection of CWD prion seeding activity in white-tailed deer muscle tissues

Chronic wasting disease (CWD) is a prion disease circulating in wild and farmed cervid populations throughout North America (United States and Canada), Europe (Finland, Norway, Sweden), and South Korea. CWD is an immediate threat to cervid heritage and the disease is causing substantial economic losses across multiple sectors. In North America, hunting and farming industries focused on the processing and consumption of white-tailed deer (WTD) venison are particularly vulnerable to CWD, as millions of WTD are consumed annually. Real-time quaking-induced conversion (RT-QuIC) is a highly sensitive assay amplifying misfolded CWD prions in vitro and has facilitated CWD prion detection in a variety of tissues and excreta. To date, no study has comprehensively examined CWD prion content across bulk skeletal muscle tissues harvested from individual CWD infected WTD. Here, we use RT-QuIC to quantify prion-seeding activity in a variety of skeletal muscles from both wild and farmed CWD-positive WTD. We successfully detected CWD prions in muscles commonly used for consumption (e.g., backstrap, tenderloin, etc.) as well as within tongue and neck samples of WTD. Our results help to establish the utility of RT-QuIC for monitoring CWD prions in venison and suggest that the method is useful for preventing CWD prions from entering animal and human food chains. Moreover, our work indicates that CWD prions are more widely distributed across skeletal muscles of infected WTD than previously reported.

molecular biology↗

bioRxiv2021

Comparison of Chronic Wasting Disease Detection Methods and Procedures: implications for free-ranging white-tailed deer (Odocoileus virginianus) surveillance and management

Throughout North America, chronic wasting disease (CWD) has emerged as perhaps the greatest threat to wild cervid populations, including white-tailed deer (Odocoileus virginianus). White-tailed deer are the most sought after big game species across North America with populations of various subspecies in nearly all Canadian provinces, the contiguous USA, and Mexico. Documented CWD cases have dramatically increased across the white-tailed deer range since the mid-1990s, including in Minnesota. CWD surveillance in free-ranging white-tailed deer and other cervid populations mainly depends upon immunodetection methods (e.g., immunohistochemistry [IHC] and enzyme-linked immunosorbent assay [ELISA]) on medial retropharyngeal lymph nodes and obex. More recent technologies centered on prion protein amplification methods of detection have shown promise as more sensitive and rapid CWD diagnostic tools. Here, we used blinded samples to test the efficacy of real time quaking-induced conversion (RT-QuIC) in comparison to ELISA and IHC for screening tissues, blood, and feces collected in 2019 from white-tailed deer in southeastern Minnesota, where CWD has been routinely detected since 2016. Our results support previous findings that RT-QuIC is a more sensitive tool for CWD detection than current antibody-based methods. Additionally, a CWD testing protocol that includes multiple lymphoid tissues (medial retropharyngeal lymph node, parotid lymph node, and palatine tonsil) per animal may effectively identify a greater number of CWD detections in a white-tailed deer population than a single sample type (i.e., medial retropharyngeal lymph nodes). These results reveal that the variability of CWD pathogenesis, sampling protocol, and testing platform must be considered for the effective detection and management of CWD throughout North America.

ecology↗

bioRxiv2019

Microbial associations and spatial proximity predict North American moose (Alces alces) gastrointestinal community composition

O_LIMicrobial communities are increasingly recognised as crucial for animal health. However, our understanding of how microbial communities are structured across wildlife populations is poor. Mechanisms such as interspecific associations are important in structuring free-living communities, but we still lack an understanding of how important interspecific associations are in structuring gut microbial communities in comparison to other factors such as host characteristics or spatial proximity of hosts.\nC_LIO_LIHere we ask how gut microbial communities are structured in a population of North American moose (Alces alces). We identify key microbial interspecific associations within the moose gut and quantify how important they are relative to key host characteristics, such as body condition, for predicting microbial community composition.\nC_LIO_LIWe sampled gut microbial communities from 55 moose in a population experiencing decline due to a myriad of factors, including pathogens and malnutrition. We examined microbial community dynamics in this population utilizing novel graphical network models that can explicitly incorporate spatial information.\nC_LIO_LIWe found that interspecific associations were the most important mechanism structuring gut microbial communities in moose and detected both positive and negative associations. Models only accounting for associations between microbes had higher predictive value compared to models including moose sex, evidence of previous pathogen exposure, or body condition. Adding spatial information on moose location further strengthened our model and allowed us to predict microbe occurrences with [~]90% accuracy.\nC_LIO_LICollectively, our results suggest that microbial interspecific associations coupled with host spatial proximity are vital in shaping infra communities in a large herbivore. In this case, previous pathogen exposure and moose body condition were not as important in predicting gut microbial community composition. The approach applied here can be used to quantify interspecific associations and gain a more nuanced understanding of the spatial and host factors shaping microbial communities in non-model hosts.\nC_LI

ecology↗