Pacific oyster holobiont in the changing environment :a microbial perspective

Animal's fitness does not depend only on its own traits, as almost every aspect of animal's biology is profoundly affected by its associated microbiota. Among other, the microbiota play an important role in health and disease: they protect their host against infections as well as act as opportunistic pathogens. The latter usually occurs if host's immune defense has been compromised due to abiotic or biotic stress. Global climate change can promote such shifts towards pathogenicity, as rising temperatures impose stress on the host and at the same time may cause increase in virulence of microbes. One example of such environmentally-dependent disease outbreaks involving opportunistic pathogens are the summer mortalities of Pacific oysters (Crassostrea gigas). Although the climate change supported the spread of this invasive intertidal bivalve to coastal habitats all over the world, it also caused the mortality events to ocurr always farther north. Involved in these mortalities are the oyster commensals and opportunistic pathogens of the genus Vibrio sp., which impose strong selection pressure and thus cause rapid adaptation of Pacific oysters to their local Vibrio populations. The Pacific oyster is also an important aquaculture species that is being routinely translocated for commercial purposes to new habitats, where it is exposed to foreign microbes. Response of the oyster-associated microbial communities to this new biotic environment or to changes in abiotic conditions is largely unknown. However, understanding how the oyster microbiota are shaped by (a)biotic disturbances...Die Fitness eines Tieres hängt nicht nur von seinen eigenen Merkmalen ab - praktisch jeder Aspekt der Biologie von Tieren wird tiefgreifend von mit ihnen assoziierten Mikroorganismen beeinflusst. Mikroorganismen spielen unter anderem eine wichtige Rolle für den Gesundheitszustand: sie schützen ihren Wirt vor Infektionen, sind gleichzeitig aber auch opportunistische Pathogene. Letzteres tritt vor allem dann auf, wenn die Immunabwehr des Wirtstiers durch biotischen oder abiotischen Stress geschwächt ist. Der globale Klimawandel kann solche Verschiebungen zu pathogenem Verhalten begünstigen, da steigende Temperaturen Stress für den Wirt bedeuten und gleichzeitig die Virulenz von Mikroorganismen erhöhen können. Ein Beispiel für solche umweltabhängigen, durch Bakterien hervorgerufenen Krankheitsausbrüche ist die Sommersterblichkeit einer Muschel, der Pazifischen Auster (Crassostrea gigas). Auch wenn der Klimawandel die Ausbreitung dieser Art in Küstenökosystemen weltweit unterstützt hat, breiten sich auf Grund steigender Temperaturen gleichzeitig die sommerlichen Austernsterben immer weiter nach Norden aus. Hervorgerufen wird das Austernsterben durch kommensalische, opportunistisch pathogene Bakterien der Gattung Vibrio, die einen starken Selektionsdruck ausüben und eine schnelle Anpassung der Austern an lokale Vibrio-Populationen bewirken. Als eine bedeutende Art in der Aquakultur und wird die Pazifische Auster aus kommerziellen Gründen häufig in neue Habitate eingeführt, wo sie neuen Mikroorganismen ausgesetzt ist. Wie mit den Austern assoziierte Mikroorganismen-Gemeinschaften auf solche neuen biotischen Umgebungen und auf Veränderungen der abiotischen Bedingungen reagieren, ist weitgehend unbekannt. Zu verstehen, wie Mikroorganismen in Austern durch (a)biotische Störungen beeinflusst werden, ist jedoch eine Voraussetzung für die Abschätzung ihrer Auswirkungen auf die Fitness von Austern..

Genomic and Transcriptomic Differentiation of Independent Invasions of the Pacific Oyster Crassostrea gigas

Upon colonizing new habitats, invasive species face a series of new selection pressures as a result of changing abiotic conditions and novel biotic interactions with native species. These new selection pressures can be accommodated by different mechanisms that act on different levels and across different time scales: (1) By changing transcriptomic profiles, species can react by plasticity within individual physiological limitations. (2) Invasive populations can adapt by fixing beneficial genetic variants in response to the newly encountered selection pressures. Here, we compare the genomic and transcriptomic landscapes of two independent invasions of the Pacific Oyster (Crassostrea gigas) into the North Sea. In detail, we combine ddRAD sequencing on the genomic level with RNAseq on the transcriptomic level to reveal outlier loci (SNPs) indicative of adaptation, as well as transcriptomic profiles from a translocation experiment to show immediate physiological reactions between two populations characterizing the two independent invasions. Generally, we found low physical congruence between differentially regulated genes and outlier loci, indicating that different genes are involved on the different time scales. Functionally matching outlier loci and differentially expressed genes were however found for spliceosomal modification of mRNA and particularly for transposon activation, indicating that these variation creating processes might be connected across eco-physiological and evolutionary time scales. By contrasting and identifying functional congruence between population outlier loci and population specific transcriptomic profiles, we can thus reveal a glimpse at the traits and processes characterizing specific mechanisms involved in successful invasions

Dual transcriptomics reveals co-evolutionary mechanisms of intestinal parasite infections in blue mussels Mytilus edulis

On theoretical grounds, antagonistic co-evolution between hosts and their parasites should be a widespread phenomenon but only received little empirical support sofar. Consequently, the underlying molecular mechanisms and evolutionary stepsremain elusive, especially in nonmodel systems. Here, we utilized the natural history of invasive parasites to document the molecular underpinnings of co-evolutionary trajectories. We applied a dual-species transcriptomics approach to experimental cross-infections of blue mussel <i>Mytilus edulis</i> hosts and their invasive parasitic copepods <i>Mytilicola intestinalis</i> from two invasion fronts in the Wadden Sea. We identified differentially regulated genes from an experimental infection contrast for hosts (infected vs. control) and a sympatry contrast (sympatric vs. allopatric combinations)for both hosts and parasites. The damage incurred by <i>Mytilicola</i> infection and the following immune response of the host were mainly reflected in cell division processes,wound healing, apoptosis and the production of reactive oxygen species(ROS). Furthermore, the functional coupling of host and parasite sympatry contrasts revealed the concerted regulation of chitin digestion by a Chitotriosidase 1 homologin hosts with several cuticle proteins in the parasite. Together with the coupled regulation of ROS producers and antagonists, these genes represent candidates that mediate the different evolutionary trajectories within the parasite’s invasion. The host–parasite combination-specific coupling of these effector mechanisms suggests that underlying recognition mechanisms create specificity and local adaptation. In this way, our study demonstrates the use of invasive species’ natural history to elucidate molecular mechanisms of host–parasite co-evolution in the wild

Spatial and Temporal Dynamics of Pacific Oyster Hemolymph Microbiota across Multiple Scales

Unveiling the factors and processes that shape the dynamics of host associated microbial communities (microbiota) under natural conditions is an important part of understanding and predicting an organism's response to a changing environment. The microbiota is shaped by host (i.e., genetic) factors as well as by the biotic and abiotic environment. Studying natural variation of microbial community composition in multiple host genetic backgrounds across spatial as well as temporal scales represents a means to untangle this complex interplay. Here, we combined a spatially-stratified with a longitudinal sampling scheme within differentiated host genetic backgrounds by reciprocally transplanting Pacific oysters between two sites in the Wadden Sea (Sylt and Texel). To further differentiate contingent site from host genetic effects, we repeatedly sampled the same individuals over a summer season to examine structure, diversity and dynamics of individual hemolymph microbiota following experimental removal of resident microbiota by antibiotic treatment. While a large proportion of microbiome variation could be attributed to immediate environmental conditions, we observed persistent effects of antibiotic treatment and translocation suggesting that hemolymph microbial community dynamics is subject to within-microbiome interactions and host population specific factors. In addition, the analysis of spatial variation revealed that the within-site microenvironmental heterogeneity resulted in high small-scale variability, as opposed to large-scale (between-site) stability. Similarly, considerable within-individual temporal variability was in contrast with the overall temporal stability at the site level. Overall, our longitudinal, spatially-stratified sampling design revealed that variation in hemolymph microbiota is strongly influenced by site and immediate environmental conditions, whereas internal microbiome dynamics and oyster-related factors add to their long-term stability. The combination of small and large scale resolution of spatial and temporal observations therefore represents a crucial but underused tool to study host-associated microbiome dynamics

Response of the human gut and saliva microbiome to urbanization in Cameroon.

Urban populations from highly industrialized countries are characterized by a lower gut bacterial diversity as well as by changes in composition compared to rural populations from less industrialized countries. To unveil the mechanisms and factors leading to this diversity loss, it is necessary to identify the factors associated with urbanization-induced shifts at a smaller geographical scale, especially in less industrialized countries. To do so, we investigated potential associations between a variety of dietary, medical, parasitological and socio-cultural factors and the gut and saliva microbiomes of 147 individuals from three populations along an urbanization gradient in Cameroon. We found that the presence of Entamoeba sp., a commensal gut protozoan, followed by stool consistency, were major determinants of the gut microbiome diversity and composition. Interestingly, urban individuals have retained most of their gut eukaryotic and bacterial diversity despite significant changes in diet compared to the rural areas, suggesting that the loss of bacterial microbiome diversity observed in industrialized areas is likely associated with medication. Finally, we observed a weak positive correlation between the gut and the saliva microbiome diversity and composition, even though the saliva microbiome is mainly shaped by habitat-related factors

Experimental Infection of the Biomphalaria glabrata Vector Snail by Schistosoma mansoni Parasites Drives Snail Microbiota Dysbiosis.

Host-parasite interaction can result in a strong alteration of the host-associated microbiota. This dysbiosis can affect the fitness of the host; can modify pathogen interaction and the outcome of diseases. Biomphalaria glabrata is the snail intermediate host of the trematode Schistosoma mansoni, the agent of human schistosomiasis, causing hundreds of thousands of deaths every year. Here, we present the first study of the snail bacterial microbiota in response to Schistosoma infection. We examined the interplay between B. glabrata, S. mansoni and host microbiota. Snails were infected and the microbiota composition was analysed by 16S rDNA amplicon sequencing approach. We demonstrated that the microbial composition of water did not affect the microbiota composition. Then, we characterised the Biomphalaria bacterial microbiota at the individual scale in both naive and infected snails. Sympatric and allopatric strains of parasites were used for infections and re-infections to analyse the modification or dysbiosis of snail microbiota in different host-parasite co-evolutionary contexts. Concomitantly, using RNAseq, we investigated the link between bacterial microbiota dysbiosis and snail anti-microbial peptide immune response. This work paves the way for a better understanding of snail/schistosome interaction and should have critical consequences in terms of snail control strategies for fighting schistosomiasis disease in the field

Hemolymph microbiome of Pacific oysters in response to temperature, temperature stress and infection

Microbiota provide their hosts with a range of beneficial services, including defense from external pathogens. However, host-associated microbial communities themselves can act as a source of opportunistic pathogens depending on the environment. Marine poikilotherms and their microbiota are strongly influenced by temperature, but experimental studies exploring how temperature affects the interactions between both parties are rare. To assess the effects of temperature, temperature stress and infection on diversity, composition and dynamics of the hemolymph microbiota of Pacific oysters (Crassostrea gigas), we conducted an experiment in a fully-crossed, three-factorial design, in which the temperature acclimated oysters (8 or 22 °C) were exposed to temperature stress and to experimental challenge with a virulent Vibrio sp. Strain. We monitored oyster survival and repeatedly collected hemolymph of dead and alive animals to determine the microbiome composition by 16s rRNA gene amplicon pyrosequencing. We found that the microbial dynamics and composition of communities in healthy animals (including infection survivors) were significantly affected by temperature and temperature stress, but not by infection. The response was mediated by changes in the incidence and abundance of operational taxonomic units (OTUs) and accompanied by little change at higher taxonomic levels, indicating dynamic stability of the hemolymph microbiome. Dead and moribund oysters, on the contrary, displayed signs of community structure disruption, characterized by very low diversity and proliferation of few OTUs. We can therefore link short-term responses of host-associated microbial communities to abiotic and biotic factors and assess the potential feedback between microbiota dynamics and host survival during disease

Polyphasic approach to the taxonomy of the selected oscillatorian strains (Cyanobacteria)

Morphology and ultrastructure of 25 oscillatorian strains was examined and phylogenetic analysis of 16S rDNA oscillatorian sequences was conducted. Genera Phormidium and Oscillatoria were shown to be polyphyletic. Although morphologically similar strains are found in different branches of the phylogenetic tree, considerable correlation between molecular, ultrastructural and some morphological and ecological traits was detected in several lineages

ACQUISIOTION OF OWNERSHIP BY LODGEMENT

Dosjelost (uzukapija), stjecanje vlasništva na stvari koja pripada drugome posjedovanjem stvari kroz vrijeme propisano zakonom. Dosjelošću se faktičko stanje nakon stanovita vremena legalizira i pretvara u pravno stanje. Dosjelost je originarni način stjecanja vlasništva, jer se vlasništvo stječe bez oslona na pravo i volju dosadašnjeg vlasnika. Vrijeme potrebno za dosjelost počinje teći kad posjednik stupi u samostalan posjed, a završava istekom posljednjeg dana vremena potrebnoga za dosjelost. U vrijeme potrebno za dosjelost uračunava se i neprekidan posjed prednika sadašnjeg posjednika koji je morao biti zakonit, istinit i pošten ili barem pošten i samostalan. Pravo vlasništva na nekretninama u društvenom vlasništvu nije se moglo steći dosjelošću zbog izričite zakonske zabrane. Tek 8. listopada 1991. kad je stupio na snagu Zakon o preuzimanju ZOVO kao zakon Republike Hrvatske, a kojim je ukinut čl. 29. počelo je teći vrijeme potrebno za dosjelost na nekretninama u društvenom vlasništvu.Usucaption, taking ownership of things that belong to another by possessing things through time prescribed by law. By the usucaption the factual situation after some time legalizes and transforms itself into legal status. Usucaption is the original way of acquiring ownership, because ownership is acquired without the right and will of the current owner. The time it takes to get starts to flow when the possessor gets into a stand alone property, and ends with the expiration of the last day of the time required for the occupation. At the time required for the occupation, there is an uninterrupted possession of the predecessor of the present possessor, who must have been legitimate, true and honest, or at least honest and independent. The right to own property in public ownership could not be acquired by law enforcement because of the explicit legal prohibition. Until October 8, 1991, when the Law on Takeover of the Law on basic ownership rights put into effect as a law of the Republic of Croatia, which cancel Art. 29. it has begun to take the time required for usucaption in social property ownership