Mass mortality events of invasive freshwater bivalves: Current understanding and potential directions for future research

Mass mortality events, the rapid, catastrophic die-off of organisms, have recently been recognized as important events in controlling population size, but are difficult to quantify given their infrequency. These events can lead to large inputs of animal carcasses into aquatic ecosystems, which can have ecosystem scale impacts. Invasive freshwater bivalves such as the Asian clam Corbicula fluminea, the zebra mussel Dreissena polymorpha, the golden mussel Limnoperna fortunei, and the Chinese pond mussel Sinanodonta woodiana can attain high densities and biomass and play important roles in aquatic ecosystems through filtration, bioturbation, and excretion. Invasive bivalve species can best be described as R-selected species and appear not to have the same tolerance to abiotic stressors as native species, causing them to be prone to mass mortality events in their invasive range. In contrast to their ecological effects while alive, the frequency and impacts of mass mortality events of invasive freshwater bivalves are not well-understood. Here we review the causes and impacts of mass mortality events, as well as identify important questions for future research. Extreme abiotic conditions, including both drought and flooding, as well as high and low temperatures were the primary drivers of mass mortality events. Short-term impacts of mass mortality events include large pulses of nitrogen and increased oxygen stress due to large amounts of soft tissue decomposition, while shells can impact habitat availability and nutrient cycling for decades. Impacts on biological communities (bacteria, fungi, and macroinvertebrates) are less studied but some examples exist concerning C. fluminea. Better documentation of mass mortality events, particularly their magnitude and frequency, is needed to fully understand the impacts invasive bivalve species have on ecosystems, especially as climate change may make mass mortality events more frequent and/or have a larger magnitude.This work was supported by funding from the School of Science and Engineering at Merrimack College

31st Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2016) : part two

Background The immunological escape of tumors represents one of the main ob- stacles to the treatment of malignancies. The blockade of PD-1 or CTLA-4 receptors represented a milestone in the history of immunotherapy. However, immune checkpoint inhibitors seem to be effective in specific cohorts of patients. It has been proposed that their efficacy relies on the presence of an immunological response. Thus, we hypothesized that disruption of the PD-L1/PD-1 axis would synergize with our oncolytic vaccine platform PeptiCRAd. Methods We used murine B16OVA in vivo tumor models and flow cytometry analysis to investigate the immunological background. Results First, we found that high-burden B16OVA tumors were refractory to combination immunotherapy. However, with a more aggressive schedule, tumors with a lower burden were more susceptible to the combination of PeptiCRAd and PD-L1 blockade. The therapy signifi- cantly increased the median survival of mice (Fig. 7). Interestingly, the reduced growth of contralaterally injected B16F10 cells sug- gested the presence of a long lasting immunological memory also against non-targeted antigens. Concerning the functional state of tumor infiltrating lymphocytes (TILs), we found that all the immune therapies would enhance the percentage of activated (PD-1pos TIM- 3neg) T lymphocytes and reduce the amount of exhausted (PD-1pos TIM-3pos) cells compared to placebo. As expected, we found that PeptiCRAd monotherapy could increase the number of antigen spe- cific CD8+ T cells compared to other treatments. However, only the combination with PD-L1 blockade could significantly increase the ra- tio between activated and exhausted pentamer positive cells (p= 0.0058), suggesting that by disrupting the PD-1/PD-L1 axis we could decrease the amount of dysfunctional antigen specific T cells. We ob- served that the anatomical location deeply influenced the state of CD4+ and CD8+ T lymphocytes. In fact, TIM-3 expression was in- creased by 2 fold on TILs compared to splenic and lymphoid T cells. In the CD8+ compartment, the expression of PD-1 on the surface seemed to be restricted to the tumor micro-environment, while CD4 + T cells had a high expression of PD-1 also in lymphoid organs. Interestingly, we found that the levels of PD-1 were significantly higher on CD8+ T cells than on CD4+ T cells into the tumor micro- environment (p < 0.0001). Conclusions In conclusion, we demonstrated that the efficacy of immune check- point inhibitors might be strongly enhanced by their combination with cancer vaccines. PeptiCRAd was able to increase the number of antigen-specific T cells and PD-L1 blockade prevented their exhaus- tion, resulting in long-lasting immunological memory and increased median survival

Liquid Cell and Environmental TEM: Frontier Techniques Applied to Geochemical Interface Reactions

International audienceLiquid cell and environmental transmission electron microscopy (LC-TEM and eTEM, respectively) are two relatively new techniques that allow for the real time measurement and in situ study of reactions between solids and liquids (LC-TEM) and solids and gases (eTEM). Both techniques offer unprecedented opportunities for exploring, at the subnanometer-scale, the dynamics and mechanisms of interfacial processes that directly control the reactivities of minerals or glasses in contact with liquids and/or gases

Liquid Cell and Environmental TEM: Frontier Techniques Applied to Geochemical Interface Reactions

International audienceLiquid cell and environmental transmission electron microscopy (LC-TEM and eTEM, respectively) are two relatively new techniques that allow for the real time measurement and in situ study of reactions between solids and liquids (LC-TEM) and solids and gases (eTEM). Both techniques offer unprecedented opportunities for exploring, at the subnanometer-scale, the dynamics and mechanisms of interfacial processes that directly control the reactivities of minerals or glasses in contact with liquids and/or gases

Liquid Cell and Environmental TEM: Frontier Techniques Applied to Geochemical Interface Reactions

International audienceLiquid cell and environmental transmission electron microscopy (LC-TEM and eTEM, respectively) are two relatively new techniques that allow for the real time measurement and in situ study of reactions between solids and liquids (LC-TEM) and solids and gases (eTEM). Both techniques offer unprecedented opportunities for exploring, at the subnanometer-scale, the dynamics and mechanisms of interfacial processes that directly control the reactivities of minerals or glasses in contact with liquids and/or gases

Liquid Cell and Environmental TEM: Frontier Techniques Applied to Geochemical Interface Reactions

International audienceLiquid cell and environmental transmission electron microscopy (LC-TEM and eTEM, respectively) are two relatively new techniques that allow for the real time measurement and in situ study of reactions between solids and liquids (LC-TEM) and solids and gases (eTEM). Both techniques offer unprecedented opportunities for exploring, at the subnanometer-scale, the dynamics and mechanisms of interfacial processes that directly control the reactivities of minerals or glasses in contact with liquids and/or gases

Nucleation pathways of sulfate minerals

International audienceSulfate minerals are abundant materials both on Earth and Mars [1]. Despite their significant role in both natural and engineered environments, MSO4-H2O systems have received surprisingly little attention in the recent flurry of studies addressing alternative (i.e. non-classical) mechanisms of solution-mediated mineral formation [2]. One exception is CaSO4, where extensive experimental work has revealed a rather complex mineralization process, involving different stages and precursor species [3,4]. Spurred by those findings, we have now extended our research using a broad variety of experimental techniques (e.g. in situ SAXS/WAXS, powder-XRD, (cryo)-TEM, potentiometric titration, induction time measurements, etc.) to other sulfate phases such as celestite (SrSO4) and barite (BaSO4). We found that these sulphate phases also undergo a multi-step formation pathway involving transient precursor species under certain physiochemical solution conditions. In particular, we present the effects of supersaturation, ionic strength, and solution hydrodynamics on the precipitation dynamics and stability/persistence of the different precursor phases. Based on the obtained experimental evidence, we construct a tentative unified model for sulfate crystallization from solution. Finally, the key questions that still need to be resolved before a holistic model of the nucleation pathway of solid phases in the MSO4-H2O system is attained will be highlighted. [1] Alpers et al., (2000) Reviews in Mineralogy and Geochemistry, 40. [2] Van Driessche et al. (2017) New Perspective on Mineral Nucleation and Growth, Springer-verlag. [3]Van Driessche et al (2012) Science, 336, 69-72. [4] Stwaski et al (2016) Nat. Commun. 7, 11177

Confined Nucleation of Strontium Sulfate

International audienceDespite their importance on Earth and Mars, sulfate minerals have largely escaped notice in the recent flurry of studies regarding alternative mechanisms of solution-mediated mineral precipitation. An exception is calcium sulfate, where experiments have revealed a complex mineralization process involving many different stages and precursors depending on the physicochemical solution conditions

Confined Nucleation of Strontium Sulfate

International audienceDespite their importance on Earth and Mars, sulfate minerals have largely escaped notice in the recent flurry of studies regarding alternative mechanisms of solution-mediated mineral precipitation. An exception is calcium sulfate, where experiments have revealed a complex mineralization process involving many different stages and precursors depending on the physicochemical solution conditions

Deciphering strontium sulfate precipitation via Ostwald’s rule of stages: From prenucleation clusters to solution-mediated phase tranformation

Multiple-step nucleation pathways have been observed during mineral formation in both inorganic and biomineral systems. These pathways can involve precursor aqueous species, amorphous intermediates, or metastable phases. Despite the widespread occurrence of these processes, elucidating the precise nucleation steps and the transformation mechanisms between each step remains a challenging task. Using a suite of potentiometric, microscopic, and spectroscopic tools, we studied the nucleation pathway of SrSO 4 as a function of the physico-chemical solution parameters. Our observations reveal that below a threshold supersaturation, nucleation is driven by bound species, akin to the prenucleation cluster model, which directly leads to the formation of the stable phase celestine, SrSO 4 . At higher supersaturations, this situation is altered, with nucleation dominated by the consumption of free ions. Importantly, this change in nucleation mechanism is coupled to the formation of a hemihydrate metastable phase, SrSO 4 · 1/2H 2 O, which eventually transforms into celestine, adhering to Ostwald’s rule of stages. This transformation is a solution-mediated process, also occurring in the presence of a fluid film and is controlled by the physico-chemical parameters of the surrounding environment. It proceeds through the dissolution of the metastable phase and the de novo crystallization of the final phase. Overall, our results reveal that ion association taking place during the prenucleation stage dictates whether the nucleation pathway goes through an intermediate phase or not. This also underlines that although Ostwald’s rule of stages is a common process, it is not a prerequisite for mineral formation—even in systems where it can occur