Temporal stability of European rocky shore assemblages: variation across a latitudinal gradient and the role of habitat‐formers

Compensatory dynamics, overyielding and statistical averaging are mechanisms promoting the temporal stability of natural communities. Using the model of European intertidal rocky shore assemblages and collating 17 datasets, we investigated how the strength of these stability‐enhancing mechanisms varies with latitude and how it can be altered by the loss of habitat‐formers (e.g. canopy‐forming macroalgae). Community stability decreased with increasing latitude, mostly as a consequence of a greater synchronization of species fluctuations. Statistical averaging and overyielding (i.e. richness effect) promoted stability, but their strength did not vary with latitude. An experimental removal of macroalgal canopies caused a strengthening of the statistical averaging effect that was consistent across the latitudinal gradient investigated. Nonetheless, the loss of canopies depressed stability by enhancing the synchronization of species fluctuations on southernmost shores, while it had weak effects on shores at higher latitudes. Variation in life‐history traits among canopy‐forming species and/or in prevailing environmental conditions across a gradient of latitude could underlie variable effects of habitat‐formers on species fluctuations. Our study shows 1) that the stability of intertidal assemblages and strength of compensatory dynamics varies with latitude, 2) that canopy‐forming macroalgae, exerting a strong control on understorey species, can influence the strength of compensatory dynamics and 3) that biological forcing (i.e. facilitation) can be as important as environmental forcing in enhancing the synchronization of species fluctuations.     

Oxidative stress induced by fumonisin B1 in continuous human and rodent neural cell cultures

Fumonisin B₁ (FB₁) is a mycotoxin produced by Fusarium verticillioides, which is a common infectant of corn and other cereal grains. Of concern to human health is also a possible airborne exposure to FB₁-producing strains of F. verticillioides, which may grow in moisture-damaged buildings. In this study, we have characterized oxidative stress-related parameters induced by FB₁ in three different neural cell lines, human SH-SY5Y neuroblastoma, rat C6 glioblastoma and mouse GT1-7 hypothalamic cells. The cells were exposed to graded doses of FB₁ between 0.1 and 100 μM for 0-144 h after which the production of reactive oxygen species (ROS), lipid peroxidation, intracellular glutathione (GSH) levels and cell viability were measured. FB₁ caused a dose-dependent increase of ROS production in C6 glioblastoma and GT1-7 hypothalamic cells but was without an effect in SH-SY5Y cells. Decreased GSH levels, increased MDA-formation, indicative of lipid peroxidation and necrotic cell death were observed in all cell lines after incubation with FB₁. These findings indicate that FB₁ induces oxidative stress in human, rat and mouse neural cell cultures.     

Fluorescent nanoparticles as labels for immunometric assay of C-reactive protein using two-photon excitation assay technology

We describe the use of fluorophore-doped nanoparticles as reporters in a recently developed ArcDia TPX bioaffinity assay technique. The ArcDia TPX technique is based on the use of polymer microspheres as solid-phase reaction carrier, fluorescent bioaffinity reagents, and detection of two-photon excited fluorescence. This new assay technique enables multiplexed, separation-free bioaffinity assays from microvolumes with high sensitivity. As a model analyte we chose C-reactive protein (CRP). The assay of CRP was optimized for assessment of CRP baseline levels using a nanoparticulate fluorescent reporter, 75 nm in diameter, and the assay performance was compared to that of CRP assay based on a molecular reporter of the same fluorophore core. The results show that using fluorescent nanoparticles as the reporter provides two orders of magnitude better sensitivity (87 fM) than using the molecular label, while no difference between precision profiles of the different assay types was found. The new assay method was applied for assessment of baseline levels of CRP in sera of apparently healthy individuals.     

Transmembrane movement of dolichol linked carbohydrates during N-glycoprotein biosynthesis in the endoplasmic reticulum

The process of N-linked glycosylation of secretory proteins is characterized by enzymatic reactions occurring on both sides of the endoplasmic reticulum (ER) membrane. On either side multiple glycosyltransferases participate in the stepwise addition of monosaccharides to core oligosaccharide unit that is attached to the lipid carrier dolichyl pyrophosphate. Cytoplasm-oriented glycosyltransferases use nucleotide-activated sugars as substrates, whereas lumen-oriented transferases that act later in the pathway make use of dolichyl phosphate-linked monosaccharides. The completely assembled core oligosaccharide is transferred to proteins on the lumenal side of the ER. The topological organization of this biosynthetic pathway requires the translocation of lipid-linked mono- and oligo-saccharides across the ER membrane. The transfer of the substrates and intermediates depend on specific translocators, i.e. so called flippases.     

Predicting the cover and richness of intertidal macroalgae in remote areas: a case study in the Antarctic Peninsula

Antarctica is an iconic region for scientific explorations as it is remote and a critical component of the global climate system. Recent climate change causes a dramatic retreat of ice in Antarctica with associated impacts to its coastal ecosystem. These anthropogenic impacts have a potential to increase habitat availability for Antarctic intertidal assemblages. Assessing the extent and ecological consequences of these changes requires us to develop accurate biotic baselines and quantitative predictive tools. In this study, we demonstrated that satellite‐based remote sensing, when used jointly with in situ ground‐truthing and machine learning algorithms, provides a powerful tool to predict the cover and richness of intertidal macroalgae. The salient finding was that the Sentinel‐based remote sensing described a significant proportion of variability in the cover and richness of Antarctic macroalgae. The highest performing models were for macroalgal richness and the cover of green algae as opposed to the model of brown and red algal cover. When expanding the geographical range of the ground‐truthing, even involving only a few sample points, it becomes possible to potentially map other Antarctic intertidal macroalgal habitats and monitor their dynamics. This is a significant milestone as logistical constraints are an integral part of the Antarctic expeditions. The method has also a potential in other remote coastal areas where extensive in situ mapping is not feasible.     

Straight GDP-tubulin protofilaments form in the presence of taxol

Microtubules exist in dynamic equilibrium, growing and shrinking by the addition or loss of tubulin dimers from the ends of protofilaments. The hydrolysis of GTP in beta-tubulin destabilizes the microtubule lattice by increasing the curvature of protofilaments in the microtubule and putting strain on the lattice. The observation that protofilament curvature depends on GTP hydrolysis suggests that microtubule destabilizers and stabilizers work by modulating the curvature of the microtubule lattice itself. Indeed, the microtubule destabilizer MCAK has been shown to increase the curvature of protofilaments during depolymerization. Here, we show that the atomic force microscopy (AFM) of individual tubulin protofilaments provides sufficient resolution to allow the imaging of single protofilaments in their native environment. By using this assay, we confirm previous results for the effects of GTP hydrolysis and MCAK on the conformation of protofilaments. We go on to show that taxol stabilizes microtubules by straightening the GDP protofilament and slowing down the transition of protofilaments from straight to a curved configuration.     

Aurora A,MCAK, and Kif18b promote Eg5-independent spindle formation

Inhibition of the microtubule (MT) motor protein Eg5 results in a mitotic arrest due to the formation of monopolar spindles, making Eg5 an attractive target for anti-cancer therapies. However, Eg5-independent pathways for bipolar spindle formation exist, which might promote resistance to treatment with Eg5 inhibitors. To identify essential components for Eg5-independent bipolar spindle formation, we performed a genome-wide siRNA screen in Eg5-independent cells (EICs). We find that the kinase Aurora A and two kinesins, MCAK and Kif18b, are essential for bipolar spindle assembly in EICs and in cells with reduced Eg5 activity. Aurora A promotes bipolar spindle assembly by phosphorylating Kif15, hereby promoting Kif15 localization to the spindle. In turn, MCAK and Kif18b promote bipolar spindle assembly by destabilizing the astral MTs. One attractive way to interpret our data is that, in the absence of MCAK and Kif18b, excessive astral MTs generate inward pushing forces on centrosomes at the cortex that inhibit centrosome separation. Together, these data suggest a novel function for astral MTs in force generation on spindle poles and how proteins involved in regulating microtubule length can contribute to bipolar spindle assembly.     

Antibody responses against SARS-CoV-2 variants induced by four different SARS-CoV-2 vaccines in health care workers in the Netherlands: A prospective cohort study

BackgroundEmerging and future SARS-CoV-2 variants may jeopardize the effectiveness of vaccination campaigns. Therefore, it is important to know how the different vaccines perform against diverse SARS-CoV-2 variants.Methods and findingsIn a prospective cohort of 165 SARS-CoV-2 naive health care workers in the Netherlands, vaccinated with either one of four vaccines (BNT162b2, mRNA-1273, AZD1222 or Ad26.COV2.S), we performed a head-to-head comparison of the ability of sera to recognize and neutralize SARS-CoV-2 variants of concern (VOCs; Alpha, Beta, Gamma, Delta and Omicron). Repeated serum sampling was performed 5 times during a year (from January 2021 till January 2022), including before and after booster vaccination with BNT162b2. Four weeks after completing the initial vaccination series, SARS-CoV-2 wild-type neutralizing antibody titers were highest in recipients of mRNA-1273, followed by recipients of BNT162b2 (geometric mean titers (GMT) of 358 [95% CI 231–556] and 214 [95% CI 153–299], respectively; p<0.05), and substantially lower in those vaccinated with the adenovirus vector-based vaccines AZD1222 and Ad26.COV2.S (GMT of 18 [95% CI 11–30] and 14 [95% CI 8–25] IU/ml, respectively; p<0.001). VOCs neutralization was reduced in all vaccine groups, with the greatest reduction in neutralization GMT observed against the Omicron variant (fold change 0.03 [95% CI 0.02–0.04], p<0.001). The booster BNT162b2 vaccination increased neutralizing antibody titers for all groups with substantial improvement against the VOCs including the Omicron variant. We used linear regression and linear mixed model analysis. All results were adjusted for possible confounding of age and sex. Study limitations include the lack of cellular immunity data.ConclusionsOverall, this study shows that the mRNA vaccines appear superior to adenovirus vector-based vaccines in inducing neutralizing antibodies against VOCs four weeks after initial vaccination and after booster vaccination, which implies the use of mRNA vaccines for both initial and booster vaccination.

Marit J. van Gils and colleagues investigate antibody responses against diverse emerging SARS-CoV-2 variants induced by four different SARS-CoV-2 vaccines in health care workers in the Netherlands.     

‘In vitro’ and ‘in situ’ decomposition of nuisance macroalgae Cladophora glomerata and Pilayella littoralis

The decomposition of two macroalgal species Cladophora glomerata (CHLOROPHYTA) and Pilayella littoralis (PHAEOPHYTA) was studied in the laboratory and field conditions. These species are known to cause the extensive macroalgal blooms in the whole coastal range of the Baltic Sea. The objective of the experiments was to determine decomposition rates of the macroalgae, follow the changes in tissue nutrient content and validate the role of benthic invertebrates in this process. In the laboratory conditions, the differences in the decomposition rates of the algae were mainly due to the oxygen conditions. The weight loss of C. glomerata was slightly higher in anaerobic conditions than in aerobic conditions. If 99% of initial dry weight of P. littoralis was lost in aerobic conditions then only 20% was lost in anaerobic conditions. In general, the loss of phosphorus and nitrogen in algal tissues followed the weight loss. As an exception, the amount of nitrogen changed very little during the decomposition of C. glomerata. In field conditions, the photosynthetic activity exceeded the decomposition rate of C. glomerata at lower temperatures in spring. The decomposition of P. littoralis was estimated at 49% of its initial dry weight. The addition of benthic invertebrates had no effect on the decomposition process. In summer, the decomposition rates were estimated at 65% for C. glomerata and 68% for P. littoralis being in the same order of magnitude as observed in laboratory conditions. If the decomposition of C. glomerata was faster at the end of the experiment, the most significant losses of weight of P. littoralis took place during the first 2 weeks of deployment. Idotea baltica significantly contributed to the loss of C. glomerata. The decomposition rate of P. littoralis was reduced by the presence of Mytilus edulis and increased by Gammarus oceanicus.