Biology subjects

Henriksson, S.

Publications and source records attributed to Henriksson, S..

8 recordsLinked to original sources

bioRxiv2026

Establishing a baseline for standardised genetic monitoring of Atlantic cod (Gadus morhua) in Sweden

Protecting populations and genetic diversity within them is critical to conserving the resilience and adaptive potential of species. Fisheries management has long had the ambition of managing species at the population level, but mainly define "fish stocks" based on geographical limits, which can lead to overfishing of sensitive populations in areas where many different populations coexist. Modern genetic methods are now sufficiently cost-effective, fast, and accurate to be integrated into fisheries management, enabling genetic identification and monitoring of fish populations. Here, we establish a genetic baseline for the commercially important fish Atlantic cod (Gadus morhua) in the waters surrounding Sweden, by using standardised sampling procedures and developing a genetic panel of 4000 single nucleotide polymorphisms (SNPs) for cost-effective assignment of population-of-origin and inversion genotypes. Using the SNP panel, we resolve the geographical distribution of three genetically distinct cod populations in the region: offshore, coastal/Western Baltic, and Eastern Baltic cod. While there is considerable spatial overlap between the three populations, they are genetically differentiated across the entire genome, as well as in genomic regions associated with chromosomal inversions. In addition, heterozygosity and effective population size estimates suggest differences in genetic diversity and rates of genetic erosion, underscoring the need to monitor the genetic diversity within each population separately. Repeating this methodology across years provides a first suggestion for establishing spatiotemporally resolved genetic monitoring of Atlantic cod in Sweden - simultaneously accounting for both population structure within the species and the genetic diversity within populations.

genomics↗

bioRxiv2025

Atlantic cod (Gadus morhua) ecotypes, not inversion frequencies, underlie divergence in egg buoyancy distribution

Life-history divergence between Atlantic cod (Gadus morhua) ecotypes in Skagerrak is maintained despite gene flow. Fjord and North Sea ecotypes differ in growth, body size, and reproductive ecology. One environmental heterogeneity in Skagerrak is salinity, as coastal habitats experience substantially lower and more variable salinities than offshore waters. Egg buoyancy is highly sensitive to salinity and represents a critical life-history trait shaping survival and recruitment. Inversions on chromosomes 2, 7, and 12 in cod are linked to salinity adaptation and might be important for egg buoyancy and survival. Here, we conducted a buoyancy test on Atlantic cod eggs, spawned from North Sea and Fjord ecotypes, using Coombs apparatus. Genotypes for the inversions on chromosomes 2, 7, and 12 and ecotype were determined in all individuals (N=242). We hypothesized that individuals with different inversion genotypes and ecotypes would have divergent buoyancies. We found that buoyancy was variable and followed a bimodal distribution sorted by ecotype, with Fjord and North Sea individuals having mean buoyancies at neutral salinity (at 7{degrees}C) of 27 and 31 ppt, respectively. Therefore, individuals with intermediate buoyancies might be selected against. This finding is consistent with our expectations, as Fjord ecotypes experience lower salinities compared to North Sea ecotypes. Interestingly, there was little evidence that the inversions on chromosomes 2, 7, and 12 impacted buoyancy. Overall, we provide experimental evidence of the relative contributions of ecotypic background and inversions on a key life history trait, which helps to explain the maintained divergence among ecotypes.

evolutionary biology↗

bioRxiv2025

Chromosomal inversions assist acute salinity and temperature adaptation in Atlantic cod (Gadus Morhua) eggs

Chromosomal inversions, on chromosomes 2, 7, and 12 in Atlantic cod (Gadus morhua), have been consistently associated with environmental gradients, particularly salinity and temperature, across the species natural range. While these correlations suggest a role for local adaptation, the underlying selective mechanisms remain unresolved. Critically, few experiments have yet tested the fitness consequences of these inversions under controlled environmental conditions. Such work is essential to establish causality. Here, we conducted an acute stressor experiment with ten treatments of combined temperature and low salinity stress. Cod eggs (N = 1265) were placed into each treatment for 24 hours, and the number of individuals that floated initially and finally was counted. The ability of an egg to float is directly related to its survival, as sunk individuals cannot survive, and individuals lose buoyancy after they die. Inversion genotypes for the inversions on chromosomes 2, 7, and 12 were determined for individuals from the T03-S25, T07-S25, T16-S25, and T16-S35 treatments. We found that sinking increased with temperature and that more individuals sank in 25 ppt than in 35 ppt after 24 hours. Interestingly, some individuals in the 25 ppt treatments recovered (sank initially but floated finally) after 24 hours. We found evidence that the inversions on chromosomes 2 and 12 might assist with temperature and salinity adaptation, respectively, in cod eggs, while the inversion on chromosome 7 did not affect floating. Our results can inform the management and conservation of this endangered species. Summary statementWe show that chromosomal inversions found in Atlantic cod help with adaptation to short-term temperature and salinity stress at the egg stage.

evolutionary biology↗

bioRxiv2024

Connectivity and population structure in a marginal sea - a review

The current biodiversity crisis calls for conservation measures that limit the negative human impact on important habitats and sensitive wild populations. To effectively protect biodiversity at all levels, including intraspecific diversity, conservation measures should be aligned with the connectivity and genetic structure of wild populations. In this review, we synthesise scientific literature on the connectivity and population structure of marine species in the Skagerrak - a marginal sea in the northeast Atlantic Ocean. We discuss the results in relation to the current management practices in the region, as well as the general transferability of our findings. The Skagerrak is one of the most intensively studied regions within this research field, and our findings show that the overall connectivity with adjacent seas is high, but asymmetric, for most species. Simultaneously, most species have populations in the Skagerrak distinct from both each other, and those in adjacent seas. Most of this population structure is associated with the convoluted Skagerrak coastline - population structure is common both among coastal populations and between coastal and offshore populations. In many mobile species, multiple populations are temporally sympatric in certain areas, but retain their genetic divergence through natal homing or other barriers to gene flow. The presence of population structure despite high connectivity is a challenge for area-based protection measures, and calls for temporally flexible management that also monitors intraspecific genetic diversity on multiple timescales.

ecology↗

bioRxiv2024

A genome-wide genetic screen identified targets for destabilizing the parasitophorous vacuole of Chlamydia trachomatis

The bacterial pathogen Chlamydia trachomatis employs the effector CpoS to suppress a host defense response that aborts intracellular bacterial growth by inducing host cell death. While conducting a CRISPR knock-out screen for genes contributing to this response, we uncovered a mutant deficient for CpoS to display a markedly increased reliance on host cellular ceramide synthesis, compensating for its diminished ability to acquire sphingolipids via modulating membrane trafficking. Employing the power of the just recently established molecular genetic toolbox for Chlamydia, we developed an innovative microscopic reporter system that revealed the mutant to thrive in unstable parasitophorous vacuoles (inclusions), characterized initially by the release of individual bacteria from otherwise intact-appearing vacuoles. CpoS-deficient inclusions were further destabilized by disruptions in ceramide synthesis, while supplementation of sphingoid bases stabilized them, also preventing the defensive host cell death response. Notably, early inclusion destabilization, achieved by simultaneous disruption of two transport routes, caused infection clearance without damaging the host cells. Overall, this study highlights the inclusions role as a refuge, demonstrates CpoS to maintain inclusion integrity by ensuring sphingolipid supply, and provides directions for a future therapeutic exploitation. SIGNIFICANCEA wide range of clinically significant microbes evolved to hide from the intrinsic defenses of their host cells by thriving within membrane-enclosed pathogen-containing vacuoles. This raises the intriguing possibility that such vacuoles could be targeted therapeutically. The bacterial pathogen Chlamydia trachomatis could be an exceptionally well-suited target for such innovative medicines given its medical importance and strict dependence on host cells. However, progress has been stalled by the lack of sensitive tools for detecting inclusion damage. Here, we resolved this major technical roadblock and uncovered the pathogen to employ the secreted effector CpoS, a modulator of membrane trafficking, to stabilize its vacuole by ensuring adequate sphingolipid supply. These methodological advances and mechanistic insights should promote the development of vacuole-destabilizing therapeutics.

microbiology↗

bioRxiv2022

Mixed origin of juvenile Atlantic cod (Gadus morhua) along the Swedish west coast

Cryptic population structure in exploited fish species poses a major challenge for fisheries management. Atlantic cod (Gadus morhua) is a species in which the presence of sympatric ecotypes has been known for a long time, for instance off the coast of Northern Norway. More recently, two sympatric ecotypes of cod have also been documented in the Skagerrak and Kattegat; one ecotype is of an apparent offshore origin and undertakes spawning migrations to the North Sea, and the other is resident at the coast throughout its life. However, their relative contributions of juveniles to the Swedish west coast remain poorly understood. The lack of adult cod along the Skagerrak and Kattegat coasts in recent years has led to the hypothesis that the offshore ecotype is the main source of juveniles to the area, but recent studies have shown large proportions of coastal cod inside Norwegian Skagerrak fjords. In this study, juvenile cod were collected at a high spatial resolution along the Swedish west coast, and genetically assigned to each of the two ecotypes. The results reveal that there is a considerable proportion of juvenile coastal cod in the southern Kattegat, Oresund, and in inshore Swedish Skagerrak, but that the offshore ecotype dominates in offshore areas. Model selection suggests that differences in bottom depth, rather than distance from the open sea, may explain the heterogenous spatial distribution of the two ecotypes. In addition, the two ecotypes displayed differences at loci known to be associated with environmental adaptation, suggesting that their spatial distribution is maintained by natural selection in response to specific environmental conditions.

genomics↗

bioRxiv2021

Cytoskeleton-extracellular matrix interaction is required to maintain mitochondrial Ca2+ control in mouse skeletal muscle fibre

Cells rapidly lose their physiological phenotype upon disruption of their extracellular matrix (ECM)-intracellular cytoskeleton interactions. Here, we investigated acute effects of ECM disruption on cellular and mitochondrial morphology, transcriptomic signatures, and Ca2+ handling in adult mouse skeletal muscle fibers. Adult skeletal muscle fibers were isolated from mouse toe muscle either by collagenase-induced dissociation of the ECM or by mechanical dissection that leaves the contiguous ECM intact. Experiments were generally performed four hours after cell isolation. At this time, there were striking differences in the gene expression patterns between fibers isolated with the two methods; 24h after cell isolation, enzymatically dissociated fibers had transcriptomic signatures resembling dystrophic phenotypes. Mitochondrial appearance was grossly similar in the two groups, but 3D electron microscopy revealed shorter and less branched mitochondria in enzymatically dissociated than in mechanically dissected fibers. Similar increases in free cytosolic [Ca2+] during repeated tetanic stimulation were accompanied by marked mitochondrial Ca2+ uptake only in enzymatically dissociated muscle fibers. The aberrant mitochondrial Ca2+ uptake was partially prevented by the mitochondrial Ca2+ uniporter inhibitor Ru360 and by cyclosporine A and NV556, which inhibit the mitochondrial protein Ppif (also called cyclophilin D). Importantly, inhibition of Ppif with NV556 significantly improved survival of mice with mitochondrial myopathy in which muscle mitochondria take up excessive amounts of Ca2+ even with an intact ECM. In conclusion, skeletal muscle fibers isolated by collagenase-induced dissociation of the ECM display aberrant mitochondrial Ca2+ uptake, which involves a Ppif-dependent mitochondrial Ca2+ influx resembling that observed in mitochondrial myopathies.

physiology↗

bioRxiv2020

Disinfection chemicals mode of action on the bacterial spore structure and their Raman spectra

Contamination of toxic spore-forming bacteria is problematic since spores can survive a plethora of disinfection chemicals. It is also problematic to rapidly detect if the disinfection chemical was active, leaving spores dead. Robust decontamination strategies, as well as reliable detection methods to identify dead from viable spores, are thus critical. Vibrational detection methods such as Raman spectroscopy has been suggested for rapid diagnostics and differentiation of live and dead spores. We investigate in this work, using laser tweezers Raman spectroscopy, the changes in Raman spectra of Bacillus thuringiensis spores treated with sporicidal agents such as chlorine dioxide, peracetic acid, and sodium hypochlorite. We also imaged treated spores using SEM and TEM to verify if any changes to the spore structure can be correlated to the Raman spectra. We found that chlorine dioxide did not change the Raman spectrum or the spore structure; peracetic acid shows a time-dependent decrease in the characteristic DNA/DPA peaks and [~]20 % of the spores were degraded and collapsed; spores treated with sodium hypochlorite show an abrupt drop in DNA and DPA peaks within 20 minutes all though the spore structure was overall intact, however, the exosporium layer was reduced. Structural changes appeared over several minutes, compared to the inactivation time of the spores, which is less than a minute. We conclude that vibrational spectroscopy provides powerful means to detect changes in spores but it might be problematic to identify if spores are live or dead after a decontamination procedure.

biophysics↗