MOSAiC Extended Acknowledgement

For years, the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), together with the international MOSAiC partners, had been planning and developing the scientific, logistical and financial concept for the implementation of the MOSAiC expedition. The planning and organization of this endeavor was an enormous e˙ort, involving more than 80 institutions from 20 countries. The number of groups and individuals that significantly contributed to the success of the drift observatory goes far beyond the scope of usual polar expeditions

Climate Science Special Report: Fourth National Climate Assessment (NCA4), Volume I

New observations and new research have increased our understanding of past, current, and future climate change since the Third U.S. National Climate Assessment (NCA3) was published in May 2014. This Climate Science Special Report (CSSR) is designed to capture that new information and build on the existing body of science in order to summarize the current state of knowledge and provide the scientific foundation for the Fourth National Climate Assessment (NCA4)

Intestinal microbiota and the innate immune system – a crosstalk in Crohn’s disease pathogenesis

Crohn’s disease (CD) is a chronic, relapsing inflammatory disorder that can occur anywhere along the gastrointestinal tract. The precise etiology of CD is still unclear but it is widely accepted that a complex series of interactions between susceptibility genes, the immune system and environmental factors are implicated in the onset and perpetuation of the disease. Increasing evidence from experimental and clinical studies implies the intestinal microbiota in disease pathogenesis, thereby supporting the hypothesis that chronic intestinal inflammation arises from an abnormal immune response against the microorganisms of the intestinal flora in genetically susceptible individuals. Given that CD patients display changes in their gut microbiota composition, collectively termed “dysbiosis,” the question raises whether the altered microbiota composition is a cause of disease or rather a consequence of the inflammatory state of the intestinal environment. This review will focus on the crosstalk between the gut microbiota and the innate immune system during intestinal inflammation, thereby unraveling the role of the microbiota in CD pathogenesis

The gut microbiome: scourge, sentinel or spectator?

The gut microbiota consists of trillions of prokaryotes that reside in the intestinal mucosa. This long-established commensalism indicates that these microbes are an integral part of the eukaryotic host. Recent research findings have implicated the dynamics of microbial function in setting thresholds for many physiological parameters. Conversely, it has been convincingly argued that dysbiosis, representing microbial imbalance, may be an important underlying factor that contributes to a variety of diseases, inside and outside the gut. This review discusses the latest findings, including enterotype classification, changes brought on by dysbiosis, gut inflammation, and metabolic mediators in an attempt to underscore the importance of the gut microbiota for human health. A cautiously optimistic idea is taking hold, invoking the gut microbiota as a medium to track, target and treat a plethora of diseases

Induction of regulatory T cells: A role for probiotics and prebiotics to suppress autoimmunity.

Regulatory T cells (Tregs) are comprised of a heterogeneous population of cells that play a vital role in suppressing inflammation and maintaining immune tolerance. Given the crucial role of Tregs in maintaining immune homeostasis, it is probably not surprising that many microbial species and their metabolites have the potential to induce Tregs. There is now great interest in the therapeutic potential of probiotics and prebiotics based strategies for a range of autoimmune disorders. This review will summarise recent findings concerning the role of probiotics and prebiotics in induction of Tregs to ameliorate the autoimmune conditions. In addition, the article is focused to explain the different mechanisms of Treg induction and function by these probiotics and prebiotics, based on the available studies till date. The article further proposes that induction of Tregs by probiotics and prebiotics could lead to the development of new therapeutic approach towards curbing the autoimmune response and as an alternative to detrimental immunosuppressive drugs

Hybrid cosmic ray measurements using the IceAct telescopes in coincidence with the IceCube and IceTop detectors

IceAct is a proposed surface array of compact (50 cm diameter) and cost-effective Imaging Air Cherenkov Telescopes installed at the site of the IceCube Neutrino Observatory at the geographic South Pole. Since January 2019, two IceAct telescope demonstrators, featuring 61 silicon photomultiplier (SiPM) pixels have been taking data in the center of the IceTop surface array during the austral winter. We present the first analysis of hybrid cosmic ray events detected by the IceAct imaging air-Cherenkov telescopes in coincidence with the IceCube Neutrino Observatory, including the IceTop surface array and the IceCube in-ice array. By featuring an energy threshold of about 10 TeV and a wide field-of-view, the IceAct telescopes show promising capabilities of improving current cosmic ray composition studies: measuring the Cherenkov light emissions in the atmosphere adds new information about the shower development not accessible with the current detectors, enabling significantly better primary particle type discrimination on a statistical basis. The hybrid measurement also allows for detailed feasibility studies of detector cross-calibration and of cosmic ray veto capabilities for neutrino analyses. We present the performance of the telescopes, the results from the analysis of two years of data, and an outlook of a hybrid simulation for a future telescope array

Host-Bacterial Symbiosis in Health and Disease

All animals live in symbiosis. Shaped by eons of co-evolution, host bacterial associations have developed into prosperous relationships creating mechanisms for mutual benefits to both microbe and host. No better example exists in biology than the astounding numbers of bacteria harbored by the lower gastrointestinal tract of mammals. The mammalian gut represents a complex ecosystem consisting of an extraordinary number of resident commensal bacteria existing in homeostasis with the host’s immune system. Most impressive about this relationship may be the concept that the host not only tolerates, but has evolved to require colonization by beneficial microorganisms, known as commensals, for various aspects of immune development and function. The microbiota provides critical signals that promote maturation of immune cells and tissues, leading to protection from infections by pathogens. Gut bacteria also appear to contribute to non-infectious immune disorders such as inflammatory bowel disease and autoimmunity. How the microbiota influences host immune responses is an active area of research with important implications for human health. This review synthesizes emerging findings and concepts that describe the mutualism between the microbiota and mammals, specifically emphasizing the role of gut bacteria in shaping an immune response that mediates the balance between health and disease. Unlocking how beneficial bacteria affect the development of the immune system may lead to novel and natural therapies based on harnessing the immunomodulatory properties of the microbiota

Interleukin-15 promotes intestinal dysbiosis with butyrate deficiency associated with increased susceptibility to colitis

Dysbiosis resulting in gut-microbiome alterations with reduced butyrate production are thought to disrupt intestinal immune homeostasis and promote complex immune disorders. However, whether and how dysbiosis develops before the onset of overt pathology remains poorly defined. Interleukin-15 (IL-15) is upregulated in distressed tissue and its overexpression is thought to predispose susceptible individuals to and have a role in the pathogenesis of celiac disease and inflammatory bowel disease (IBD). Although the immunological roles of IL-15 have been largely studied, its potential impact on the microbiota remains unexplored. Analysis of 16S ribosomal RNA-based inventories of bacterial communities in mice overexpressing IL-15 in the intestinal epithelium (villin-IL-15 transgenic (v-IL-15tg) mice) shows distinct changes in the composition of the intestinal bacteria. Although some alterations are specific to individual intestinal compartments, others are found across the ileum, cecum and feces. In particular, IL-15 overexpression restructures the composition of the microbiota with a decrease in butyrate-producing bacteria that is associated with a reduction in luminal butyrate levels across all intestinal compartments. Fecal microbiota transplant experiments of wild-type and v-IL-15tg microbiota into germ-free mice further indicate that diminishing butyrate concentration observed in the intestinal lumen of v-IL-15tg mice is the result of intrinsic alterations in the microbiota induced by IL-15. This reconfiguration of the microbiota is associated with increased susceptibility to dextran sodium sulfate-induced colitis. Altogether, this study reveals that IL-15 impacts butyrate-producing bacteria and lowers butyrate levels in the absence of overt pathology, which represent events that precede and promote intestinal inflammatory diseases

Pathways and modification of the upper and intermediate waters of the Arctic Ocean,

The purpose of this study is to investigate the pathways and the ventilation of source water masses of the upper and intermediate waters of the Arctic Ocean. For the Arctic and subarctic domain, a coupled ice-ocean general circulation model is set up to be integrated for several decades. It is driven by a climatological seasonal cycle of monthly mean atmospheric data from 1980-89 and by restored sea surface salinities. Passive tracers are used to visualise and interpret the modelled flow and to compare it with observations.The model is able to reproduce known features of the Arctic Ocean circulation like the inflow of two branches of Atlantic origin via the Fram Strait and the Barents Sea and their subsequent passage at mid depths in several cyclonic circulation cells. The fate of these Atlantic source water masses, river water and Bering Strait inflow water in the model are studied. The branch crossing the Barents Sea is subject to an intense heat loss and ice formation. As a result water of this branch leaves the shelf towards the central part of the Arctic Ocean not only at the surface but also in denser varieties which finally feed the central Arctic at halocline and mid depths. The lightest part turns northward and finally westward joining the Transpolar Drift, the densest part (200-1000 m depth) move eastward along the continental slope. A similar path is taken by the Atlantic water branch from the Fram Strait. The inflowing branch over the Barents Sea turns out to be the dominant source for the lower Atlantic Water layer in the Arctic Ocean in this investigation.Atlantic tracers starting in Fram Strait need 6 years to reach the northern Laptev Sea slope. Travel times to return to Fram Strait are 15 - 20 years along the Lomonossov Ridge and about 30 years along the continental slope of the Canadian Basin. Tracers which mark the Pacific Water or the Mackenzie river water flow eastward and leave the Arctic mainly via the Canadian Archipelago. The Siberian river water tracers at the surface penetrate far into the Canadian Basin before they join the Transpolar Drift. The travel times of the river water from the river mouths are 2-3 years to the shelf edge and 12-14 years to Fram Strait