El picoplàncton marí, reserva d'organismes i funcions

6 pages, 7 figuresEl plàncton marí està format pel conjunt d'organismes de mides, tipus tròfics i afiliacions taxonòmiques variades que viuen en suspensió en la columna d’aigua. S’ha estimat que el fitoplàncton és responsable de la meitat de la producció primària del planeta. Aquesta enorme producció pot fluir a través de la cadena d’herbívors (zooplàncton i peixos), circular per la xarxa tròfica microbiana (bacteris i protozous) o sedimentar de la capa fòtica. La importància relativa d’aquestes tres vies, en general modulada per la disponibilitat de nutrients degut a processos hidrodinàmics, té grans repercussions per als recursos pesquers, la bomba biològica del carboni i la regulació del clima. Els microorganismes (< 200 µm) són els principals participants del metabolisme del sistema marí, tant del cicle biogeoquímic del carboni (producció i respiració) com dels altres cicles. Gran part d’aquest metabolisme està mediat per microorganismes molt petits (de 0.2 a 2 µm) i relativament desconeguts, el picoplàncton (Sherr & Sherr 2000). Es té una idea força bona de l’abundància i activitat d’alguns tipus de picoplàncton fàcilment reconeixibles (bacteris, cianobacteris, protistes fototròfics i heterotròfics, Fig. 1), que es tracten com a grups homogenis que suposadament funcionen de manera similar. Tanmateix, cadascun d’aquests tipus inclou una enorme diversitat, tant filogenètica (diferents espècies) com funcional (cada espècie pot ocupar un nínxol ecològic diferent), que queda sovint amagada sota una notable uniformitat morfològica. En aquest article presentaré i discutiré breument alguns avanços recents sobre la diversitat (dècada dels noranta) i la funció (segle XXI) del picoplàncton marí. Aquests avanços estan aportant un coneixement fonamental per a la millor comprensió del funcionament dels ecosistemes marins (Karl 2002)Peer Reviewe

Xarxes invisibles : L'art d'esbrinar quants microorganismes marins hi ha, quins són i què fan

7 pages, 5 figures, 1 tableThe greater part of the biomass of living creatures in the ocean is made up of microorganisms. Fundamental to explaining the way those ecosystems work they are responsible for most of the breathing taking place in marine waters and for the heterotrophic use of organic composts. All in all it was not until the end of the 20th century with the development of microscopic instrumentation that their task has been appreciated, putting into doubt the dominant belief that algae are the main generators of primary production (binding carbon). Nowadays, genomics has enabled us to gain insight into the functions of microorganisms that we did not know were present in the plankton.Peer Reviewe

Significant year-round effect of small mixotrophic flagellates on bacterioplankton in an oligotrophic coastal system

14 pages, 7 figures, 1 tableThe seasonal variation in the grazing effect of mixotrophic flagellates on bacterioplankton was assessed during an annual cycle in an oligotrophic coastal station in the northwest Mediterranean Sea. Ingestion rates of fluorescently labeled bacteria were estimated for different size categories of phytoflagellates (PF) and heterotrophic flagellates (HF) in short-term experiments and compared with long-term grazing estimates and published empirical models. The mixotrophic flagellates included haptophyte-like cells, cryptophytes, and dinoflagellates. The group-specific grazing rates (SGR) averaged 1.1 (3–5 µm PF), 1.3 (5–20 µm PF), 4.0 (<5 µm HF), and 15.4 bacteria individual-1 h-1 (5–20 µm HF). Lower SGR but higher abundances of PF resulted in an average mixotroph contribution of 50% to the total flagellate grazing. Remarkably, the effect was relatively high all through the year (35–65%). Regardless of the presence of chloroplasts, flagellates <5 mm in size accounted, on average, for about 80% of total flagellate bacterivory and ingested a large percentage of their cell carbon per day from bacteria. Soluble reactive phosphorus concentration was negatively correlated with the ingestion rate of both groups of PF, suggesting that mixotrophic flagellates would be using their phagotrophic capability to obtain phosphorus when this nutrient is limiting. HF grazing activity showed a marked seasonality, with grazing being higher during the warmer seasons, and clearance rates were positively correlated with water temperature. Total bacterivory accounted for most of the bacterial production. Short-term and long-term bacterivory measurements were highly correlated, confirming that the smallest flagellates were the main causative agent of bacterial loss. The bacterivory values were also well correlated to a published empirical model that considers HF as the only bacterivorous. However, this model underestimated (up to 50%) total flagellate grazing during periods of high effect of mixotrophic flagellatesThis study was supported mainly by a EU project (EVK3-CT-2002-00078) and a Spanish post-doctoral fellowship (SB2001-0166) and also partially funded by three projects supported by the Spanish government (REN2001-2120/MAR; CTM2004-12631/MAR; CTM2004-02586/MAR)Peer reviewe

Accessing the genomic information of unculturable oceanic picoeukaryotes by combining multiple single cells

Mangot, Jean-François et al.-- 12 pages, 7 figures, 2 tables, supplementary information https://dx.doi.org/10.1038/srep41498Pico-sized eukaryotes play key roles in the functioning of marine ecosystems, but we still have a limited knowledge on their ecology and evolution. The MAST-4 lineage is of particular interest, since it is widespread in surface oceans, presents ecotypic differentiation and has defied culturing efforts so far. Single cell genomics (SCG) are promising tools to retrieve genomic information from these uncultured organisms. However, SCG are based on whole genome amplification, which normally introduces amplification biases that limit the amount of genomic data retrieved from a single cell. Here, we increase the recovery of genomic information from two MAST-4 lineages by co-assembling short reads from multiple Single Amplified Genomes (SAGs) belonging to evolutionary closely related cells. We found that complementary genomic information is retrieved from different SAGs, generating co-assembly that features >74% of genome recovery, against about 20% when assembled individually. Even though this approach is not aimed at generating high-quality draft genomes, it allows accessing to the genomic information of microbes that would otherwise remain unreachable. Since most of the picoeukaryotes still remain uncultured, our work serves as a proof-of-concept that can be applied to other taxa in order to extract genomic data and address new ecological and evolutionary questionsThis work was supported by the US NSF grants DEB-1031049 and OCE-821374 (to M.E.S.), by the ANR French projects Oceanomics (ANR-11-BTBR-0008, to C.V.), France Génomique (ANR-10-INBS-09, to P.W.), and Prometheus (ANR-09-PCS-GENM_217, to O.J.), by the EU project SINGEK (H2020-MSCA-ITN-2015-675752, to R.M.), and by the Spanish project MEFISTO (CTM2013-43767-P, MINECO). J.-F.M. was supported by a Marie Curie Intra-European Fellowship (PIEF-GA-2012-331190, EU). R.L. was supported by Juan de la Cierva (JCI-2010-06594, MINECO) and Ramón y Cajal fellowships (RYC-2013-12554, MINECO)Peer Reviewe

Single cell ecology

Cells are the building blocks of life, from single-celled microbes through to multi-cellular organisms. To understand a multitude of biological processes we need to understand how cells behave, how they interact with each other and how they respond to their environment. The use of new methodologies is changing the way we study cells allowing us to study them on minute scales and in unprecedented detail. These same methods are allowing researchers to begin to sample the vast diversity of microbes that dominate natural environments. The aim of this special issue is to bring together research and perspectives on the application of new approaches to understand the biological properties of cells, including how they interact with other biological entities

UPC system for the 2016 MediaEval multimodal person discovery in broadcast TV task

The UPC system works by extracting monomodal signal segments (face tracks, speech segments) that overlap with the person names overlaid in the video signal. These segments are assigned directly with the name of the person and used as a reference to compare against the non-overlapping (unassigned) signal segments. This process is performed independently both on the speech and video signals. A simple fusion scheme is used to combine both monomodal annotations into a single one.Postprint (published version

Púrpura de Schönlein Henoch. A propòsit d'un cas en una esportista

Presentem el cas d'una esportista de natació sincronitzada de 15 anys amb púrpura de Schönlein-Henoch (també coneguda per púrpura anafilactoide), una vasculitis sistèmica de petits vasos, considerada la més freqüent en la infància, i que afecta preferentment nens entre 3 i 15 anys, amb prevalença del sexe masculí sobre el femení (2:1). L'afectació va ser exclusivament cutània en forma de petèquies, amb diversos brots de lesions dèrmiques, i la seva evolució va ser benigna i autolimitada; no va necessitar més tractament que el repòs esportiu (com a prevenció de possibles complicacions més greus) i els controls clínics i analítics adients