Comparative Population Genomics Unveils Congruent Secondary Suture Zone in Southwest Pacific Hydrothermal Vents.

How the interplay of biotic and abiotic factors shapes current genetic diversity at the community level remains an open question, particularly in the deep sea. Comparative phylogeography of multiple species can reveal the influence of past climatic events, geographic barriers, and species life history traits on spatial patterns of genetic structure across lineages. To shed light on the factors that shape community-level genetic variation and to improve our understanding of deep-sea biogeographic patterns, we conducted a comparative population genomics study on seven hydrothermal vent species co-distributed in the Back-Arc Basins of the Southwest Pacific region.

A community perspective on the concept of marine holobionts: current status, challenges, and future directions.

Host-microbe interactions play crucial roles in marine ecosystems. However, we still have very little understanding of the mechanisms that govern these relationships, the evolutionary processes that shape them, and their ecological consequences. The holobiont concept is a renewed paradigm in biology that can help to describe and understand these complex systems.

Real-life implementation of guidelines on the hospital-to-home transition for older patients: a cohort study in general practice.

Background: hospital discharge is a critical event for older patients. The French guidelines recommended the swift transmission of a discharge summary to the general practitioner (GP) and a primary care consultation within 7 days. The relevance and feasibility of these guidelines have not previously been assessed.

Global host molecular perturbations upon in situ loss of bacterial endosymbionts in the deep-sea mussel Bathymodiolus azoricus assessed using proteomics and transcriptomics.

Background: Colonization of deep-sea hydrothermal vents by most invertebrates was made efficient through their adaptation to a symbiotic lifestyle with chemosynthetic bacteria, the primary producers in these ecosystems. Anatomical adaptations such as the establishment of specialized cells or organs have been evidenced in numerous deep-sea invertebrates. However, very few studies detailed global inter-dependencies between host and symbionts in these ecosystems.

High rates of apoptosis visualized in the symbiont-bearing gills of deep-sea Bathymodiolus mussels.

Symbiosis between Bathymodiolus and Gammaproteobacteria allows these deep-sea mussels to live in toxic environments such as hydrothermal vents and cold seeps. The quantity of endosymbionts within the gill-bacteriocytes appears to vary according to the hosts environment; however, the mechanisms of endosymbiont population size regulation remain obscure. We investigated the possibility of a control of endosymbiont density by apoptosis, a programmed cell death, in three mussel species.

Qualitative thematic analysis of the phenomenology of near-death experiences.

Near-death experiences (NDEs) refer to profound psychological events that can have an important impact on the experiencers' (NDErs) lives. Previous studies have shown that NDEs memories are phenomenologically rich. In the present study, we therefore aimed to extract the common themes (referred to as "features" in the NDE literature) reported by NDErs by analyzing all the concepts stored in the narratives of their experiences.

Identification and gene expression of multiple peptidoglycan recognition proteins (PGRPs) in the deep-sea mussel Bathymodiolus azoricus, involvement in symbiosis?

The relationship between the deep-sea mussel Bathymodiolus azoricus and its thiotrophic (SOX) and methanotrophic (MOX) symbionts has been ecologically and functionally well studied. Endosymbiosis is common in deep-sea hydrothermal vent fauna, yet little is known about the molecular mechanisms underlying the regulation of interactions between host and symbionts. In this study we focused on a group of pattern recognition receptors (PRR), called PGRPs that are able to recognize the peptidoglycan of bacterial cell wall.

Multiple I-Type Lysozymes in the Hydrothermal Vent Mussel Bathymodiolus azoricus and Their Role in Symbiotic Plasticity.

The aim of this study was first to identify lysozymes paralogs in the deep sea mussel Bathymodiolus azoricus then to measure their relative expression or activity in different tissue or conditions. B. azoricus is a bivalve that lives close to hydrothermal chimney in the Mid-Atlantic Ridge (MAR).

Physico-Chemical Heterogeneity of Organic-Rich Sediments in the Rifle Aquifer, CO: Impact on Uranium Biogeochemistry.

The Rifle alluvial aquifer along the Colorado River in west central Colorado contains fine-grained, diffusion-limited sediment lenses that are substantially enriched in organic carbon and sulfides, as well as uranium, from previous milling operations. These naturally reduced zones (NRZs) coincide spatially with a persistent uranium groundwater plume. There is concern that uranium release from NRZs is contributing to plume persistence or will do so in the future.

Selective forces acting during multi-domain protein evolution: the case of multi-domain globins.

Multi-domain proteins form the majority of proteins in eukaryotes. During their formation by tandem duplication or gene fusion, new interactions between domains may arise as a result of the structurally-forced proximity of domains. The proper function of the formed proteins likely required the molecular adjustment of these stress zones by specific amino acid replacements, which should be detectable by the molecular signature of selection that governed their changes.

Globin's structure and function in vesicomyid bivalves from the Gulf of Guinea cold seeps as an adaptation to life in reduced sediments.

Vesicomyid bivalves form dense clam beds in both deep-sea cold seeps and hydrothermal vents. The species diversity within this family raises questions about niche separation and specific adaptations. To compare their abilities to withstand hypoxia, we have studied the structure and function of erythrocyte hemoglobin (Hb) and foot myoglobin (Mb) from two vesicomyid species, Christineconcha regab and Laubiericoncha chuni, collected from the Regab pockmark in the Gulf of Guinea at a depth of 3,000 m.

A new barrier to dispersal trapped old genetic clines that escaped the Easter Microplate tension zone of the Pacific vent mussels.

Comparative phylogeography of deep-sea hydrothermal vent species has uncovered several genetic breaks between populations inhabiting northern and southern latitudes of the East Pacific Rise. However, the geographic width and position of genetic clines are variable among species. In this report, we further characterize the position and strength of barriers to gene flow between populations of the deep-sea vent mussel Bathymodiolus thermophilus.

Conjugating effects of symbionts and environmental factors on gene expression in deep-sea hydrothermal vent mussels.

Background: The deep-sea hydrothermal vent mussel Bathymodiolus azoricus harbors thiotrophic and methanotrophic symbiotic bacteria in its gills. While the symbiotic relationship between this hydrothermal mussel and these chemoautotrophic bacteria has been described, the molecular processes involved in the cross-talking between symbionts and host, in the maintenance of the symbiois, in the influence of environmental parameters on gene expression, and in transcriptome variation across individuals remain poorly understood. In an attempt to understand how, and to what extent, this double symbiosis affects host gene expression, we used a transcriptomic approach to identify genes potentially regulated by symbiont characteristics, environmental conditions or both.

Insights into metazoan evolution from Alvinella pompejana cDNAs.

Background: Alvinella pompejana is a representative of Annelids, a key phylum for evo-devo studies that is still poorly studied at the sequence level. A. pompejana inhabits deep-sea hydrothermal vents and is currently known as one of the most thermotolerant Eukaryotes in marine environments, withstanding the largest known chemical and thermal ranges (from 5 to 105°C).

Determining gene flow and the influence of selection across the equatorial barrier of the East Pacific Rise in the tube-dwelling polychaete Alvinella pompejana.

Background: Comparative phylogeography recently performed on the mitochondrial cytochrome oxidase I (mtCOI) gene from seven deep-sea vent species suggested that the East Pacific Rise fauna has undergone a vicariant event with the emergence of a north/south physical barrier at the Equator 1-2 Mya. Within this specialised fauna, the tube-dwelling polychaete Alvinella pompejana showed reciprocal monophyly at mtCOI on each side of the Equator (9 degrees 50'N/7 degrees 25'S), suggesting potential, ongoing allopatric speciation. However, the development of a barrier to gene flow is a long and complex process.

Origin and evolution of the unique tetra-domain hemoglobin from the hydrothermal vent scale worm Branchipolynoe.

Hemoglobin is the most common respiratory pigment in annelids. It can be intra or extracellular, and this latter type can form large multimeric complexes. The hydrothermal vent scale worms Branchipolynoe symmytilida and Branchipolynoe seepensis express an extracellular tetra-domain hemoglobin (Hb) that is unique in annelids.

Comparative phylogeography among hydrothermal vent species along the East Pacific Rise reveals vicariant processes and population expansion in the South.

The use of sequence polymorphism from individual mitochondrial genes to infer past demography has recently proved controversial because of the recurrence of selective sweeps acting over genes and the need for unlinked multilocus data sets. However, comparative analyses using several species for one gene and/or multiple genes for one species can serve as a test for potential selective effects and clarify our understanding of historical demographic effects. This study compares nucleotide polymorphisms in mitochondrial cytochrome oxidase I across seven deep-sea hydrothermal vent species that live along the volcanically active East Pacific Rise.

Structural study of Carcinus maenas hemocyanin by native ESI-MS: interaction with L-lactate and divalent cations.

The interaction of L-lactate and divalent cations with Carcinus maenas hemocyanin has been probed by electrospray ionization mass spectrometry under conditions preserving noncovalent interactions (native ESI-MS). C. maenas native hemocyanin in the hemolymph occurs mainly as dodecamers and to a lesser extent as hexamers.

The structural analysis of large noncovalent oxygen binding proteins by MALLS and ESI-MS: a review on annelid hexagonal bilayer hemoglobin and crustacean hemocyanin.

Understanding the function of macromolecular complexes is related to a precise knowledge of their structure. These large complexes are often fragile high molecular mass noncovalent multimeric proteins. Classical biochemical methods for determination of their native mass and subunit composition were used to resolve their quaternary structure, sometimes leading to different models.

[Chemoautotrophic endosymbioses: contemporary models for symbiogenesis?].

Oxygen appears to be one of the key factors in understanding the evolution of life on Earth. Almost absent during more than 2 billion years, its subsequent increase is correlated with the emergence of oxygenic photosynthesis by Cyanobacteria, followed by aerobic Prokaryotes and eventually Eukaryotes, all primitively aerobic, and more recently, the development of complex multicellular organisms. However, in some reduced environments, still present at the surface of the Earth and even more so in ocean depths (hydrothermal vents, cold seeps, massive organic falls,.

Identification of proteins involved in the functioning of Riftia pachyptila symbiosis by Subtractive Suppression Hybridization.

Background: Since its discovery around deep sea hydrothermal vents of the Galapagos Rift about 30 years ago, the chemoautotrophic symbiosis between the vestimentiferan tubeworm Riftia pachyptila and its symbiotic sulfide-oxidizing gamma-proteobacteria has been extensively studied. However, studies on the tubeworm host were essentially targeted, biochemical approaches. We decided to use a global molecular approach to identify new proteins involved in metabolite exchanges and assimilation by the host.

Identification, sequencing, and localization of a new carbonic anhydrase transcript from the hydrothermal vent tubeworm Riftia pachyptila.

The vestimentiferan annelid Riftia pachyptila forms dense populations at hydrothermal vents along the East Pacific Rise at a depth of 2600 m. It harbors CO(2)-assimilating sulfide-oxidizing bacteria that provide all of its nutrition. To find specific host transcripts that could be important for the functioning of this symbiosis, we used a subtractive suppression hybridization approach to identify plume- or trophosome-specific proteins.

Respiratory adaptations to the deep-sea hydrothermal vent environment: the case of Segonzacia mesatlantica, a crab from the Mid-Atlantic Ridge.

Segonzacia mesatlantica (Crustacea; Decapoda; Brachyura) is the only endemic crab species known from the Mid-Atlantic Ridge (MAR) hydrothermal vents. Known from all explored sites in the Atlantic, its wide distribution makes this species a model to study physiological adaptation, and specifically respiratory strategies. Native haemocyanin (Hc) comprises four non-covalent associations in equilibrium formed by monomers, hexamers, dodecamers and octadecamers made up of approximately 75 kDa polypeptide chains.