Peptidylarginine Deiminase (PAD) and Post-Translational Protein Deimination—Novel Insights into Alveolata Metabolism, Epigenetic Regulation and Host–Pathogen Interactions

The alveolates (Superphylum Alveolata) comprise a group of primarily single-celled eukaryotes that have adopted extremely diverse modes of nutrition, such as predation, photoautotrophy and parasitism. The alveolates consists of several major phyla including the apicomplexans, a large group of unicellular, spore forming obligate intracellular parasites, and chromerids, which are believed to be the phototrophic ancestors of the parasitic apicomplexans. Molecular pathways involved in Alveolata host–pathogen interactions, epigenetic regulation and metabolism in parasite development remain to be fully understood. Peptidylarginine deiminases (PADs) are a phylogenetically conserved enzyme family which causes post-translational protein deimination, affecting protein function through the conversion of arginine to citrulline in a wide range of target proteins, contributing to protein moonlighting in physiological and pathological processes. The identification of deiminated protein targets in alveolate parasites may therefore provide novel insight into pathogen survival and host-pathogen interactions. The current study assessed PAD homologues and deiminated protein profiles of two alveolate parasites, Piridium sociabile (Chromerida) and Merocystis kathae (Apicomplexa). Histological analysis verified strong cytoplasmic PAD expression in both Alveolates, detected deiminated proteins in nuclear and cytoplasmic compartments of the alveolate parasites and verified the presence of citrullinated histone H3 in Alveolata nucleus, indicating roles in epigenetic regulation. Histone H3 citrullination was also found significantly elevated in the host tissue, indicative of neutrophil extracellular trap formation, a host-defence mechanism against a range of pathogens, particularly those that are too large for phagocytosis. Proteomic analysis of deiminated proteins from both Alveolata identified GO and KEGG pathways strongly relating to metabolic and genetic regulation, with some species-specific differences between the apicomplexan and the chromerid. Our findings provide novel insights into roles for the conserved PAD/ADI enzyme family in the regulation of metabolic and epigenetic pathways in alveolate parasites, possibly also relating to their life cycle and host–pathogen interactions

Experimental challenges with Renibacterium salmoninarum in Arctic charr Salvelinus alpinus

Arctic charr Salvelinus alpinus L. is an important species in Icelandic aquaculture and the most common wild salmonid in Iceland. A study on the course of infection with the bacterium Renibacterium salmoninarum was conducted using 3 different challenge methods in brackish and fresh water. Bacterial isolation, ELISA and PCR tests were used for detection of the bacterium in multiple organ samples. In an experiment, run for 34 wk in brackish water, infection was established by intraperitoneal injection with 5 × 106 colony forming units (CFU) fish-1. There were external and internal symptoms of bacterial kidney disease (BKD) and mortalities between 6 and 13 wk after injection. A cohabitation trial was run simultaneously and infection was well established after 4 wk, as demonstrated by the detection methods applied. Symptoms of BKD were not seen and all but 1 cohabitant survived. In a separate experiment, infection was established by pumping a fixed amount of water from a tank with fingerlings infected by intraperitoneal injection into tanks with naïve fish, in fresh or brackish water, for 6 wk. Fish in the inflow tanks were reared for an additional 3 wk. There were neither macroscopic symptoms nor mortalities. ELISA and PCR tests showed that infection started to take hold after 3 wk. The challenge trials demonstrated that Arctic charr is susceptible to R. salmoninarum. Cohabitation and inflow of water from tanks with infected fish provide useful models for further studies on R. salmoninarum infection acquired in a natural way in Arctic charr.The authors are indebted to Islands-bleikja at Grindavik (Samherji hf., Akureyri, Iceland) for providing the fish used in the study, to the staff at Sudurnes Science and Learning Centre for attendance to the experimental fish and to Sigurour Snorrason and Asthildur Erlingsdottir for constructive criticism on the manuscript. This work received grants from the AVS R&D Fund of Ministry of Fisheries and Agriculture in Iceland no. R 10 0093-10 and R 13 074-13.Peer Reviewe

Hidden Infections and Changing Environments

0000-0001-7279-715XThe file attached is the Accepted/final draft post-refereeing version of the article

Harmless sea snail parasite causes mass mortalities in numerous commercial scallop populations in the northern hemisphere

Publisher's version (útgefin grein)Apicomplexans comprise a group of unicellular, often highly pathogenic, obligate parasites exploiting either one or two hosts to complete a full reproductive cycle. For decades, various scallop populations have suffered cyclical mass mortality events, several of which shown to be caused by apicomplexan infections. We report the first dual mollusc life cycle for an apicomplexan: a species highly pathogenic in various pectinid bivalve species, but apathogenic when infecting the common whelk as Merocystis kathae. The sympatric distribution of the common whelk and scallops in the North Atlantic makes transmission extremely effective, occurring via the gastrointestinal tract, by scavenging and predation in whelks and unselective filter feeding in scallops. Infective sporozoites from whelks utilize scallops´ haemocytes to reach muscular tissue, where asexual reproduction occurs. Phylogenetically, this apicomplexan is robustly placed within the Aggregatidae and its inclusion in analyses supports a common ancestry with other basal invertebrate apicomplexans. Scallops seem able to regulate lowlevel infections of M. kathae as they exist in normal populations while epizootics occur during high levels of exposure from locally infected whelks. A targeted removal of whelks from valuable scallop grounds would be advantageous to minimize the occurrence of M. kathae epizootics and prevent damaging economic losses.We acknowledge the staff at the Marine and Freshwater Research Institute in Iceland and Grant Campell at Scothatch scallop ranch, for sampling of research material.Peer Reviewe

Redescription and phylogenetic position of Myxobolus ‘eglefini’ and Myxobolus platessae n. comb. (Myxosporea), parasites in the cartilage of some North Atlantic marine fishes, with notes on the phylogeny and classification of the Platysporina

publishedVersio

Literacy in Denmark. Country Report. Short Version

European Literacy Policy Network (ELINET

Multiple Independent Origins of Apicomplexan-Like Parasites

The apicomplexans are a group of obligate animal pathogens that include Plasmodium (malaria), Toxoplasma (toxoplasmosis), and Cryptosporidium (cryptosporidiosis) [1]. They are an extremely diverse and specious group but are nevertheless united by a distinctive suite of cytoskeletal and secretory structures related to infection, called the apical complex, which is used to recognize and gain entry into animal host cells. The apicomplexans are also known to have evolved from free-living photosynthetic ancestors and retain a relict plastid (the apicoplast), which is non-photosynthetic but houses a number of other essential metabolic pathways [2]. Their closest relatives include a mix of both photosynthetic algae (chromerids) and non-photosynthetic microbial predators (colpodellids) [3]. Genomic analyses of these free-living relatives have revealed a great deal about how the alga-parasite transition may have taken place, as well as origins of parasitism more generally [4]. Here, we show that, despite the surprisingly complex origin of apicomplexans from algae, this transition actually occurred at least three times independently. Using single-cell genomics and transcriptomics from diverse uncultivated parasites, we find that two genera previously classified within the Apicomplexa, Piridium and Platyproteum, form separately branching lineages in phylogenomic analyses. Both retain cryptic plastids with genomic and metabolic features convergent with apicomplexans. These findings suggest a predilection in this lineage for both the convergent loss of photosynthesis and transition to parasitism, resulting in multiple lineages of superficially similar animal parasites

A portrait of the immune response to proliferative kidney disease (PKD) in rainbow trout

This work was supported by the European Commission under the Horizon H2020 research and innovation programme (Grant H2020‐634429 ParaFishControl) and by the European Research Council (ERC Consolidator Grant 2016 725061 TEMUBLYM). CB was supported by the SNSF Post‐Doc Mobility grant P400PB_183824.Peer reviewedPublisher PD