Search

A range of volatile organic compounds (VOCs) have been found to be released during zooplankton grazing on microalgae cultivated for commercial purposes. However, production of grazing-derived VOCs from environmentally relevant species and their potential contribution to oceanic emissions to the atmosphere remains largely unexplored. Here, we aimed to qualitatively explore the suite of VOCs produced due to grazing using laboratory cultures of the marine microalga Isochrysis galbana and the herbivorous heterotrophic dinoflagellate Oxyrrhis marina with and without antibiotic treatment. The VOCs were measured using a Vocus proton-transfer-reaction time-of-flight mass spectrometer, coupled to a segmented flow coil equilibrator. We found alternative increases of dimethyl sulfide by up to 0.2 nmol dm−3 and methanethiol by up to 10 pmol dm−3 depending on the presence or absence of bacteria regulated by antibiotic treatment. Additionally, toluene and xylene increased by about 30 pmol dm−3 and 10 pmol dm−3, respectively during grazing only, supporting a biological source for these compounds. Overall, our results highlight that VOCs beyond dimethyl sulfide are released due to grazing, and prompt further quantification of this source in budgets and process-based understanding of VOC cycling in the surface ocean

Yaiza Castillo, bioquímica i doctora en biotecnologia ens parla dels microorganismes marins

[Resumen] Introducción: La prematuridad es una condición de primera urgencia sanitaria experimentada por un gran número de neonatos. Constituye la causa de múltiples morbilidades, incluidas neurológicas y respiratorias, debido a la propia interrupción del desarrollo embrionario y las exposiciones posteriores en la UCIN en la procura de la supervivencia de esta población. La ventilación mecánica, tanto invasiva como no invasiva, es un método utilizado con frecuencia en este campo por sus beneficios, pero su uso puede generar e incluso agravar efectos perjudiciales en la salud derivando en un peor pronóstico del crecimiento y funcionamiento del cerebro. Objetivo: El objetivo principal de esta revisión sistemática es identificar el papel de la ventilación mecánica como posible causa de alteraciones estructurales en el cerebro inmaduro de los niños prematuros. Material y método: Se realizó una búsqueda bibliográfica en las bases de datos Cochrane Library Plus, Pubmed, Medline, Scopus, Dialnet Plus, Web Of Science y LILACS; durante abril y mayo del año 2021. Posteriormente, se valoraría el nivel de evidencia y el grado de recomendación mediante la escala Oxford, y la calidad metodológica mediante el JCR. Resultados: Un total de 6 artículos (5 estudios de cohortes y 1 revisión bibliográfica) cumplieron los criterios de inclusión y fueron seleccionados para la elaboración de esta revisión. Un estudio de cohortes era retrospectivo y analizaba el riesgo asociado a la ventilación mecánica y patologías del neurodesarrollo (físicas y cognitivas) encontrando una relación directa entre ambos. El resto eran prospectivos, de los cuales tres señalaron que esta técnica influía negativamente en toda la masa cerebral (sustancia blanca y sustancia gris); y un cuarto indicó que la ventilación mecánica provoca anomalías en el electroencefalograma por amplitud, pero que no perduran en el tiempo. Por último, la revisión bibliográfica describía los procesos fisiopatológicos desencadenados po, [Abstract] Background: Prematurity is a condition of first health emergency experienced by a large number of newborns. It is the cause of multiple morbidities, including neurological and respiratory, due to the interruption of embryonic development itself and subsequent exposures in the NICU in the search for the survival of this population. Mechanical ventilation, both invasive and non-invasive, is a method frequently used in this field due to its benefits, but its use can generate and even aggravate harmful effects on health, resulting in a worse prognosis for brain growth and function. Objective: The aim of this systematic review is to identify the role of mechanical ventilation as a possible cause of structural alterations in the immature brain of premature infants. Methods: A bibliographic search was made in the Cochrane Library Plus, Pubmed, Medline, Scopus, Dianet Plus, Web of Science and LILACS databases; during April and May 2021. Subsequently, the level of evidence and the grade of recommendation would be assessed using the Oxford scale, and the methodological quality using the JCR. Outcomes: A total of 6 articles (5 cohort studies and 1 bibliographic review) met the inclusion criteria and were selected for the drafting of this review. A cohort study was retrospective and analysed the risk associated with mechanical ventilation and neurodevelopmental pathologies (physical and cognitive), finding a direct relationship between the two. The rest were prospective, of which three indicated that this technique had a negative influence on the total brain volume (white matter and gray matter); and a fourth study indicated that mechanical ventilation causes abnormalities in the aEEG, but that they do not persist over time. Finally, the bibliographic review described the pathophysiological processes triggered by mechanical ventilation and compared its different modalities. Conclusions: After the analysis of the scientific literature, it was concluded that mechanical, [Resumo] Introdución: A prematuridade é unha condición de primeira urxencia sanitaria experimentada por un gran número de neonatos. Constitúe a causa de múltiples morbilidades, incluídas neurolóxicas e respiratorias, debido á propia interrupción do desenvolvemento embrionario e as exposicións posteriores na UCIN na procura da supervivencia desta poboación. A ventilación mecánica, tanto invasiva como non invasiva, é un método utilizado con frecuencia neste campo polos seus beneficios, pero o seu uso pode xerar e incluso agravar efectos prexudiciais na saúde derivando nun peor prognóstico do crecemento e funcionamento do cerebro. Obxectivo: O obxectivo principal desta revisión sistemática é identificar o papel da ventilación mecánica como posible causa de alteracións estruturais no cerebro inmaturo dos nenos prematuros. Material e método: Realizouse unha busca bibliográfica nas bases de datos Cochrane Library Plus, Pubmed, Medline, Scopus, Dialnet Plus, Web Of Science y LILACS; durante abril e maio do ano 2021. Posteriormente, valorouse o nivel de evidencia e o grado de recomendación mediante a escala Oxford, e a calidade metodolóxica mediante o JCR. Resultados: Un total de 6 artigos (5 estudos de cohortes e 1 revisión bibliográfica) cumpriron os criterios de inclusión e foron seleccionados para a elaboración desta revisión. Un estudo de cohortes era retrospectivo e analizaba o resgo asociado á ventilación mecánica e patoloxías do desenvolvemento neurolóxico (físicas y cognitivas) atopando unha relación directa entre ambos. O resto eran prospectivos, dos cales tres sinalaron que esta técnica influía negativamente en toda a masa cerebral (sustancia branca e sustancia gris); e un cuarto indicou que a ventilación mecánica provoca anomalías no electroencefalograma por amplitude, pero non perduran no tempo. Por último, a revisión bibliográfica describía os procesos fisiopatolóxicos desencadeados pola ventilación mecánica e comparaba as súas distintas modalidades. Conclusió

Els virus marins són les entitats biològiques més abundants que hi ha al mar. En un mil·lilitre (ml) en trobem deu milions i en tot l’oceà 1030. Infecten a tots els éssers vius des de balenes fins a procariotes (bacteris i arqueus). Sent aquests darrers molt abundants (un milió per ml), són els seus hostes preferits. Per tant, la major proporció de virus que hi ha al mar són bacteriòfags (del grec, ‘menjadors de bacteris’) de doble cadena de DNA encara que també se’n troben d’RNA. Tenen un paper cabdal a les xarxes tròfiques microbianes. Quan lisen els seus hostes (per exemple, bacteris i fitoplàncton), el contingut cel·lular ric en matèria orgànica dissolta passa a la columna d’aigua. Part d’aquesta matèria orgànica pot ser aprofitada pels bacteris per créixer i remineralitzada a nutrients inorgànics (N, P, S), que podran ser utilitzats pel fitoplàncton. Per tant, els virus desenvolupen un paper important en el control de l’abundància i diversitat de les comunitats microbianes i en els cicles biogeoquímics a l’oceà. Però no tots els virus són lítics; n’hi ha que s’integren en el genoma de l’hoste i esdevenen pròfags. El pròfag passa a ser un virus temperat i la cèl·lula portadora és el lisogen i pot transmetre’l a moltes generacions (cicle lisogènic), ja que la constitució genètica del bacteri canvia degut als nous gens que aporta el virus. A conseqüència de canvis ambientals i altres factors, el cicle lisogènic pot revertir al cicle lític, i llençar la nova progènie vírica fora amb el contingut cel·lular de l’hoste. Els diferents tipus de cicle d’infecció (lític, Marine viruses are the most abundant biological entities in the sea. We find 10 million in 1 ml and 1030 in the entire ocean. They infect all living beings, from whales to prokaryotes (bacteria and archaea). Since prokaryotes are very abundant (1 million per ml), they are the viruses’ favourite hosts. The largest proportion of viruses in the sea are double-stranded DNA bacteriophages, although RNA viruses are also found. In marine systems, viruses play a key role in the food web. When they lyse their hosts, they cause the cellular content rich in dissolved organic matter and recycled inorganic nutrients to enter the water column, where it is used by other bacteria and/or by photosynthetic microorganisms for their growth. Consequently, viruses control the abundance and diversity of the microbial communities and play a key role in the biogeochemical cycles in the ocean. But not all viruses are lytic: some integrate themselves into their host’s genome and become prophages or temperate viruses. The carrier cell of the prophage or temperate virus is a lysogen and the prophage can be transmitted to further generations, causing changes in its genome. Environmental changes or cellular stress could revert the lysogenic cycle to the lytic cycle, releasing new viral progeny with the cellular content of the host. The different types of infection (lytic and lysogenic) make marine viruses the largest reservoir of genetic diversity, either stealing genes and/or transferring them to their hosts. Lastly, viruses also could play an important role in the regulation of the climate, contributing to the production of condensation nuclei that act as seeds for the formation of clouds, considered cooling elements of our planet.Keywords: viruses, microorganisms, lysis, lysogeny, condensation nuclei.

We explored how changes of viral abundance and community composition among four contrasting regions in the Southern Ocean relied on physicochemical and microbiological traits. During January–February 2015, we visited areas north and south of the South Orkney Islands (NSO and SSO) characterized by low temperature and salinity and high inorganic nutrient concentration, north of South Georgia Island (NSG) and west of Anvers Island (WA), which have relatively higher temperatures and lower inorganic nutrient concentrations. Surface viral abundance (VA) was highest in NSG (21.50 ± 10.70 × 106 viruses mL−1) and lowest in SSO (2.96 ± 1.48 × 106 viruses mL−1). VA was positively correlated with temperature, prokaryote abundance and prokaryotic heterotrophic production, chlorophyll a, diatoms, haptophytes, fluorescent organic matter, and isoprene concentration, and was negatively correlated with inorganic nutrients (NO3−, SiO42−, PO43−), and dimethyl sulfide (DMS) concentrations. Viral communities determined by randomly amplified polymorphic DNA–polymerase chain reaction (RAPD-PCR) were grouped according to the sampling location, being more similar within them than among regions. The first two axes of a canonical correspondence analysis, including physicochemical (temperature, salinity, inorganic nutrients—NO3−, SiO42−, and dimethyl sulfoniopropionate -DMSP- and isoprene concentrations) and microbiological (chlorophyll a, haptophytes and diatom, and prokaryote abundance and prokaryotic heterotrophic production) factors accounted for 62.9% of the variance. The first axis, temperature-related, accounted for 33.8%; the second one, salinity-related, accounted for 29.1%. Thus, different environmental situations likely select different hosts for viruses, leading to distinct viral communities.

[EN] Marine viruses are the most abundant biological entities in the sea. We find 10 million in 1 ml and 1030 in the entire ocean. They infect all living beings, from whales to prokaryotes (bacteria and archaea). Since prokaryotes are very abundant (1 million per ml), they are the viruses’ favourite hosts. The largest proportion of viruses in the sea are double-stranded DNA bacteriophages, although RNA viruses are also found. In marine systems, viruses play a key role in the food web. When they lyse their hosts, they cause the cellular content rich in dissolved organic matter and recycled inorganic nutrients to enter the water column, where it is used by other bacteria and/or by photosynthetic microorganisms for their growth. Consequently, viruses control the abundance and diversity of the microbial communities and play a key role in the biogeochemical cycles in the ocean. But not all viruses are lytic: some integrate themselves into their host’s genome and become prophages or temperate viruses. The carrier cell of the prophage or temperate virus is a lysogen and the prophage can be transmitted to further generations, causing changes in its genome. Environmental changes or cellular stress could revert the lysogenic cycle to the lytic cycle, releasing new viral progeny with the cellular content of the host. The different types of infection (lytic and lysogenic) make marine viruses the largest reservoir of genetic diversity, either stealing genes and/or transferring them to their hosts. Lastly, viruses also could play an important role in the regulation of the climate, contributing to the production of condensation nuclei that act as seeds for the formation of clouds, considered cooling elements of our planet, [CAT] Els virus marins són les entitats biològiques més abundants que hi ha al mar. En un mil·lilitre (ml) en trobem deu milions i en tot l’oceà 1030. Infecten a tots els éssers vius des de balenes fins a procariotes (bacteris i arqueus). Sent aquests darrers molt abundants (un milió per ml), són els seus hostes preferits. Per tant, la major proporció de virus que hi ha al mar són bacteriòfags (del grec, ‘menjadors de bacteris’) de doble cadena de DNA encara que també se’n troben d’RNA. Tenen un paper cabdal a les xarxes tròfiques microbianes. Quan lisen els seus hostes (per exemple, bacteris i fitoplàncton), el contingut cel·lular ric en matèria orgànica dissolta passa a la columna d’aigua. Part d’aquesta matèria orgànica pot ser aprofitada pels bacteris per créixer i remineralitzada a nutrients inorgànics (N, P, S), que podran ser utilitzats pel fitoplàncton. Per tant, els virus desenvolupen un paper important en el control de l’abundància i diversitat de les comunitats microbianes i en els cicles biogeoquímics a l’oceà. Però no tots els virus són lítics; n’hi ha que s’integren en el genoma de l’hoste i esdevenen pròfags. El pròfag passa a ser un virus temperat i la cèl·lula portadora és el lisogen i pot transmetre’l a moltes generacions (cicle lisogènic), ja que la constitució genètica del bacteri canvia degut als nous gens que aporta el virus. A conseqüència de canvis ambientals i altres factors, el cicle lisogènic pot revertir al cicle lític, i llençar la nova progènie vírica fora amb el contingut cel·lular de l’hoste. Els diferents tipus de cicle d’infecció (lític i lisogènic) fan que els virus marins siguin el reservori més gran de diversitat genètica, ja que transfereixen gens dels hostes infectats a d’altres hostes. Finalment, els virus també tenen un paper important en la regulació del clima, ja que contribueixen a la producció de nuclis de condensació que són la llavor per a la formació de núvols, els quals es consideren elements que intervenen en el refr

[EN] In 1892, the Russian biologist Dmitri Ivanovsky described a non-bacterial pathogen that infected tobacco plants. He did not know it, but he had just discovered a new biological entity: viruses. These infectious agents are still a conundrum for scientists. It is not even known if they are alive or not, since they do not have their own metabolism and they need cells (prokaryotes and eukaryotes) to be able to reproduce. They could therefore be defined as ‘obligate parasites’. What completely well known is that viruses are the most abundant biological units on earth. In total, it is estimated that there are 10^31 viruses inhabiting the planet, a number that far exceeds the number of stars (10^24) in the observable universe. To illustrate this, it is said that, placed side by side, viruses could form a chain of about 10 million light years. [...], [ES] En el año 1892, el biólogo ruso Dmitri Ivanovsky describió un patógeno no-bacteriano que infectaba a las plantas del tabaco. No lo sabía, pero acababa de descubrir una nueva entidad biológica: los virus. Estos agentes infecciosos siguen siendo en la actualidad un enigma. Ni siquiera se sabe si están vivos o no, ya que no tienen metabolismo propio y les hacen falta células (procariotas y eucariotas) para poder reproducirse. Se podrían definir, por lo tanto, como ‘parásitos obligados’. Lo que sí que se sabe a ciencia cierta es que los virus son las unidades biológicas más abundantes del planeta. En total, se estima que habitan en la Tierra aproximadamente 10^31 virus, una cifra que supera con creces la cantidad de estrellas (10^24) que hay en el universo observable. Para ilustrarlo, se dice que, puestos uno al lado del otro, los virus podrían llegar a formar una cadena de unos 10 millones de años luz. [...], [CAT] L'any 1892, el biòleg rus Dmitri Ivanovsky va descriure un patogen no-bacterià que infectava les plantes del tabac. No ho sabia, però acabava de descobrir una nova entitat biològica: els virus. Aquests agents infecciosos continuen sent en l'actualitat un enigma. Ni tan sols se sap del cert si estan vius o no, ja que no tenen metabolisme propi i els calen cèl·lules (procariotes i eucariotes) per poder reproduir-se. Es podrien definir, per tant, com a ‘paràsits obligats’. El que sí que se sap del cert és que els virus són les unitats biològiques més abundants del planeta. En total, s'estima que habiten a la Terra aproximadament 10^31 virus, una xifra que supera amb escreix la quantitat d'estrelles (10^24) que hi ha a l'univers observable. Per il·lustrar-ho, es diu que, posats un al costat de l'altre, els virus podrien arribar a formar una cadena d'uns 10 milions d'anys llum. [...]

One of the major challenges in viral ecology is to assess the impact of viruses in controlling the abundance of specific hosts in the environment. To this end, techniques that enable the detection and quantification of virus-host interactions at the single-cell level are essential. With this goal in mind, we implemented virus fluorescence in situ hybridization (VirusFISH) using as a model the marine picoeukaryote Ostreococcus tauri and its virus Ostreococcus tauri virus 5 (OtV5). VirusFISH allowed the visualization and quantification of the proportion of infected cells during an infection cycle in experimental conditions. We were also able to quantify the abundance of free viruses released during cell lysis, discriminating OtV5 from other mid-level fluorescence phages in our non-axenic infected culture that were not easily distinguishable with flow cytometry. Our results showed that although the major lysis of the culture occurred between 24 and 48 h after OtV5 inoculation, some new viruses were already produced between 8 and 24 h. With this work, we demonstrate that VirusFISH is a promising technique to study specific virus-host interactions in non-axenic cultures and establish a framework for its application in complex natural communities

We explored how changes of viral abundance and community composition among four contrasting regions in the Southern Ocean relied on physicochemical and microbiological traits. During January–February 2015, we visited areas north and south of the South Orkney Islands (NSO and SSO) characterized by low temperature and salinity and high inorganic nutrient concentration, north of South Georgia Island (NSG) and west of Anvers Island (WA), which have relatively higher temperatures and lower inorganic nutrient concentrations. Surface viral abundance (VA) was highest in NSG (21.50 ± 10.70 × 106 viruses mL−1) and lowest in SSO (2.96 ± 1.48 × 106 viruses mL−1). VA was positively correlated with temperature, prokaryote abundance and prokaryotic heterotrophic production, chlorophyll a, diatoms, haptophytes, fluorescent organic matter, and isoprene concentration, and was negatively correlated with inorganic nutrients (NO3−, SiO42−, PO43−), and dimethyl sulfide (DMS) concentrations. Viral communities determined by randomly amplified polymorphic DNA–polymerase chain reaction (RAPD-PCR) were grouped according to the sampling location, being more similar within them than among regions. The first two axes of a canonical correspondence analysis, including physicochemical (temperature, salinity, inorganic nutrients—NO3−, SiO42−, and dimethyl sulfoniopropionate -DMSP- and isoprene concentrations) and microbiological (chlorophyll a, haptophytes and diatom, and prokaryote abundance and prokaryotic heterotrophic production) factors accounted for 62.9% of the variance. The first axis, temperature-related, accounted for 33.8%; the second one, salinity-related, accounted for 29.1%. Thus, different environmental situations likely select different hosts for viruses, leading to distinct viral communities

The VirusFISH method requires that we design, synthetize and label the probes that will hybridize to our virus of interest. In this section we explain what is needed for this purpose

Viruses are the most abundant biological entities on Earth and have fundamental ecological roles in controlling microbial communities. Yet, although their diversity is being increasingly explored, little is known about the extent of viral interactions with their protist hosts as most studies are limited to a few cultivated species. Here, we exploit the potential of single‐cell genomics to unveil viral associations in 65 individual cells of 11 essentially uncultured stramenopiles lineages sampled during the Tara Oceans expedition. We identified viral signals in 57% of the cells, covering nearly every lineage and with narrow host specificity signal. Only seven out of the 64 detected viruses displayed homologies to known viral sequences. A search for our viral sequences in global ocean metagenomes showed that they were preferentially found at the DCM and within the 0.2–3 µm size fraction. Some of the viral signals were widely distributed, while others geographically constrained. Among the viral signals we detected an endogenous mavirus virophage potentially integrated within the nuclear genome of two distant uncultured stramenopiles. Virophages have been previously reported as a cell's defence mechanism against other viruses, and may therefore play an important ecological role in regulating protist populations. Our results point to single‐cell genomics as a powerful tool to investigate viral associations in uncultured protists, suggesting a wide distribution of these relationships, and providing new insights into the global viral diversity

Marine viruses are the most abundant entities (107 viruses mL-1) and the main reservoir of genomic diversity in the oceans. Theyare key players in the marine microbial food webs, controlling the abundances and shaping the diversity of microbes, and thus im-pacting the biogeochemical cycles. Several questions have arisen since the discovery of the relevance of viruses in the marine en-vironment: who are they? How many are there? and especially, who infects whom? Nowadays, it is possible to count the viralabundances (e.g. through flow cytometry, epifluorescence microscopy, etc.), but there is still a large gap on knowing who infectswhom. Although the development of high throughput sequencing gives information on viral diversity and potential hosts, it is difficultto visualize each specific virus-host interaction. With that goal in mind, we are currently working with a technique called VirusFISH(Virus Fluorescent in situ Hybridization). With this technique, we are able to visualize, thanks to fluorescence microscopy, the inter-actions between viruses and their eukaryotic hosts at different stages over time. Also, we are able to detect and count a specificvirus within the natural community. How does it work? We design and synthetize several fluorescently labeled probes (~10 DNAmolecules of 300bp length each), that will specifically attach to the genome of our virus of interest. Thus, we can monitor the timingand magnitude of infections in natural microbial communities, and understand the impact of the virus in the abundance and functionof its host

In aquatic systems it is described that lysogeny (a prophage inserted in the DNA of the bacterial host) should be the dominant viral life cycle in oligotrophic waters, which are characterized by a low nutrient concentration, low primary production and slow growing bacterial cells. While, according to the kill the winner hypothesis lytic phages prevail in high productive systems where bacterial hosts are abundant. However, the analysis of several public datasets revealed that lysogeny increased in eutrophic systems. These findings are in agreement with the recently proposed Piggyback-the–Winner model, which also suggests that lysogeny is more successful than the lytic cycle when bacterial hosts are abundant. The model assumes that viruses “exploit” their hosts through lysogeny instead of killing them, making this fact advantageous for both. Thus, the prophage stage of the virus is propagated from the “happily” growing bacteria to the new bacterial generations, being the host protected by the prophage from new viral infections and predation by grazers. The finding that aquatic environments with high host abundances has fewer virus per host when the host abundance is low, challenge the paradigm on the relative roles of lytic and lysogeny viral strategies

Marine viruses are the most abundant biological entities in marine ecosystems, and due to their life cycle’ they have an impact on biogeochemical cycles, contributing in making life possible in the oceans. These days, there is a large and well-established knowledge on what regards to viruses’ role in the marine ecosystems. They influence the particle size distribution, particle sinking rates, bacterial and algal biodiversity, and the release of organic compounds derived from biological metabolism. However, little is known about the influence that the interaction between environmental and biological factors may have on marine viruses’ communities. In Antarctic and the sub-Antarctic waters, phytoplankton blooms occur during the Austral summer, and is then when viruses and bacteria can reach their greatest abundance and activity rates. These algal blooms are usually dominated by different taxonomic groups: diatoms, dinoflagellates, haptophytes, cryptomones, etc. Besides, phytoplankton communities are accompanied by bacterial communities, and they are influenced by environmental conditions. Then, all these interactions may have a role in the function and structure of marine viruses. To test which are the main drivers contributing to shape viral community distribution and structure, four environmentally contrasting locations were sampled during the Austral summer-2015. Three locations were near Orkney and Anvers Islands close to the Antarctic Peninsula, and one in the South Georgia Islands in the sub-Antarctic Ocean. These locations presented different physicochemical and biological conditions (e.g. temperature, salinity, viral and bacterial abundance, phytoplankton taxa...). We characterized the physicochemical conditions and the phytoplankton community of these locations, and we studied the marine viral community structure by using the fingerprint technique: Randomly amplified polymorphic DNA-PCR (RAPD) that allowed to group similar viral communities. Indeed, the four

The emergence of single cell genomics (SCG) has revolutionized microbial ecology by retrieving genomic information from microorganisms that are ecologically relevant but still refractory to being cultured. This approach offers also the possibility to untangle putative ecological interactions between uncultured protists and other organisms at a single cell level (i.e. infection, prey capture or symbiosis). Here, we have investigated the presence of viral signal among cells of 11 Stramenopiles protist lineages isolated during the Tara Oceans expedition. On a total of 65 Single Amplified Genomes (SAGs) analyzed, 37 presented viral signatures. The new detected viral contigs, generally fragmented, were possible to assign to known viral genomes thanks to new published bioinformatics tools. We were able to relate one of these viral sequences to a Mavirus virophage, which occurred in 4 SAGs belonging to a pigmented uncultured Chrysophyte (Chrysophyte G1) and in 1 SAG affiliated to the clade A of MAST-3 (MAST-3A), among other viral and phage signals in 4 other different SAGs lineages. The virophages associated to the Chrysophyte G1 and MAST-3A lineages were over 95% similar to the annotated Maverick-related virophage infecting Cafeteria roenbergensis. Virophages are DNA viruses readily integrating into an eukaryotic genome (provirophage) where they act as an inducible antiviral defense system against a larger infectious virus (for instance CroV in Cafeteria roenbergensis). Moreover, an investigation of their global distribution in open sea environments will be performed using metagenomic and metatranscriptomic data from the Tara Ocean expedition

Microbes comprise >90% of the biomass in the world's oceans, drive biogeochemical cycles, and have turnover rates ranging from hours to days. Despite the central role of microbes in marine systems, there is no robust way to evaluate taxon-specific mortality. Previously, we reported that there are millions of free-ribosomes per mL of seawater that are released by cell lysis, and that these can be used to estimate taxon-specific cell lysis. Here, ribosome decay and production rates were used to estimate taxon-specific microbial mortality in surface waters of the Red Sea. Free-ribosome production, indicative of cell lysis, was detected in 953 out of 1308 prokaryotic taxa after incubations with or without mitomycin C. In 261 taxa (~27%), ribosome production only occurred with mitomycin C addition, suggesting that lysis was caused by prophage induction. Overall, 60 different dynamic patterns of free-ribosomes and cells were detected across five time points in the experiment. Using the rate of ribosome production, and ribosome copy number per cell, the mortality rate of prokaryotes was estimated to average 1.3±0.64 d-1 in the controls and 2.47±0.89 d-1 in Mitomycin C treatments, and varied among taxa and treatments. Some taxa had high rates of mortality, including the genera Acinetobacter, AEGEAN-169 marine group, Phyllobacterium, Microbacterium, Halomonas and Thalassospira. Our results show high-mortality-rates are coupled to high growth rates and high relative-abundances, suggesting that r-selected have higher lysis rates. The ability to estimate taxon-specific mortality rate as the result of cell lysis adds an important tool in our quest to explain the distribution, abundance and roles of specific microbial taxa in nature

During the Austral summer 2009 we studied three areas surrounding the Antarctic Peninsula: the Bellingshausen Sea, the Bransfield Strait and the Weddell Sea. We aimed to investigate, whether viruses or protists were the main agents inducing prokaryotic mortality rates, and the sensitivity to temperature of prokaryotic heterotrophic production and mortality based on the activation energy (Ea) for each process. Seawater samples were taken at seven depths (0.1–100 m) to quantify viruses, prokaryotes and protists abundances, and heterotrophic prokaryotic production (PHP). Viral lytic production, lysogeny, and mortality rates of prokaryotes due to viruses and protists were estimated at surface (0.1–1 m) and at the Deep Fluorescence Maximum (DFM, 12–55 m) at eight representative stations of the three areas. The average viral lytic production ranged from 1.0 ± 0.3 × 107 viruses ml−1 d−1 in the Bellingshausen Sea to1.3 ± 0.7 × 107 viruses ml−1 d−1 in the Bransfield Strait, while lysogeny, when detectable, recorded the lowest value in the Bellingshausen Sea (0.05 ± 0.05 × 107 viruses ml−1 d−1) and the highest in the Weddell Sea (4.3 ± 3.5 × 107 viruses ml−1 d−1). Average mortality rates due to viruses ranged from 9.7 ± 6.1 × 104 cells ml−1 d−1 in the Weddell Sea to 14.3 ± 4.0 × 104 cells ml−1 d−1 in the Bellingshausen Sea, and were higher than averaged grazing rates in the Weddell Sea (5.9 ± 1.1 × 104 cells ml−1 d−1) and in the Bellingshausen Sea (6.8 ± 0.9 × 104 cells ml−1 d−1). The highest impact on prokaryotes by viruses and main differences between viral and protists activities were observed in surface samples: 17.8 ± 6.8 × 104 cells ml−1 d−1 and 6.5 ± 3.9 × 104 cells ml−1 d−1 in the Weddell Sea; 22.1 ± 9.6 × 104 cells ml−1 d−1 and 11.6 ± 1.4 × 104 cells ml−1 d−1 in the Bransfield Strait; and 16.1 ± 5.7 × 104 cells ml−1 d−1 and 7.9 ± 2.6 × 104 cells ml−1 d−1 in the Bellingshausen Sea, respectively. Furthermore, the rate of lysed cells and PHP showed higher sensitivity to

Viruses are a key component of marine ecosystems, but the assessment of their global role in regulating microbial communities and the flux of carbon is precluded by a paucity of data, particularly in the deep ocean. We assessed patterns in viral abundance and production and the role of viral lysis as a driver of prokaryote mortality, from surface to bathypelagic layers, across the tropical and subtropical oceans. Viral abundance showed significant differences between oceans in the epipelagic and mesopelagic, but not in the bathypelagic, and decreased with depth, with an average power-law scaling exponent of −1.03 km−1 from an average of 7.76 × 106 viruses ml−1 in the epipelagic to 0.62 × 106 viruses ml−1 in the bathypelagic layer with an average integrated (0 to 4000 m) viral stock of about 0.004 to 0.044 g C m−2, half of which is found below 775 m. Lysogenic viral production was higher than lytic viral production in surface waters, whereas the opposite was found in the bathypelagic, where prokaryotic mortality due to viruses was estimated to be 60 times higher than grazing. Free viruses had turnover times of 0.1 days in the bathypelagic, revealing that viruses in the bathypelagic are highly dynamic. On the basis of the rates of lysed prokaryotic cells, we estimated that viruses release 145 Gt C year−1 in the global tropical and subtropical oceans. The active viral processes reported here demonstrate the importance of viruses in the production of dissolved organic carbon in the dark ocean, a major pathway in carbon cycling

The developments of techniques that allow us to obtain single amplified genomes (SAGs) have revolutionized the study of microorganisms without the need of culturing them. Here, we show the results of a SAG study on two kinds of marine Stramenopiles: the Chrysophite sp. G1 and the Marine Stramenopile 3A (MAST-3A). Our aim was to unveil new viral signatures present in SAGs using the data obtained in the TaraOcean expedition. The results obtained show the occurrence of a complete Mavirus virophage inside the genome of Chrysophite G1, here called G1_Chryso_Virophage, and another complete virophage inside the genome of MAST3A, here called MAST3A_Virophage. The G1_Chryso_Virophage is 95.72% similar with the annotated Maverick-related virophage infecting Cafeteria roerbengensis, while MAST3A_Virophage presents a 94.8% of similarity (alignments performed with MAFFT). Therefore, we conclude that we unveil two different kinds of new virophages, from the same family but infecting different species

Marine viruses, together with other planktonic microorganisms, play an important role on the marine ecosystem functioning, and their activity can contribute on the marine aerosol composition. During the interdisciplinary PEGASO expedition, we visit four contrasting areas of the Southern Ocean (Antarctic and sub-antarctic), with high (South Giorgia Island) to low degree (Orkney Islands) of microplanktonic biomass and activity and derived secondary compounds concentration. In this study we aimed to (I) describe different viral community abundance and structures (distribution and diversity) among four contrasted areas; (II) relate them with their main hosts (bacteria and phytoplankton) as well as with physicochemical variables and (III) uncover their relation with metabolic secondary compounds generated by marine microbiological activity, which in turn, can be related with the marine aerosol composition

The developments of techniques that allow us to obtain single amplified genomes (SAGs) have revolutionized the study of microorganisms without the need of culturing them. Here, we show the results of a SAG study on two kinds of marine Stramenopiles: the Chrysophite sp. G1 and the Marine Stramenopile 3A (MAST-3A). Our aim was to unveil new viral signatures present in SAGs using the data obtained in the TaraOcean expedition. The results obtained show the occurrence of a complete Mavirus virophage inside the genome of Chrysophite G1, here called G1_Chryso_Virophage, and another complete virophage inside the genome of MAST3A, here called MAST3A_Virophage. The G1_Chryso_Virophage is 95.72% similar with the annotated Maverick-related virophage infecting Cafeteria roerbengensis, while MAST3A_Virophage presents a 94.8% of similarity (alignments performed with MAFFT). Therefore, we conclude that we unveil two different kinds of new virophages, from the same family but infecting different species

During the Austral summer 2009 we studied three areas surrounding the Antarctic Peninsula: the Bellingshausen Sea, the Bransfield Strait and the Weddell Sea. We aimed to investigate, whether viruses or protists were the main agents inducing prokaryotic mortality rates, and the sensitivity to temperature of prokaryotic heterotrophic production and mortality based on the activation energy (Ea) for each process. Seawater samples were taken at seven depths (0.1–100 m) to quantify viruses, prokaryotes and protists abundances, and heterotrophic prokaryotic production (PHP). Viral lytic production, lysogeny, and mortality rates of prokaryotes due to viruses and protists were estimated at surface (0.1–1 m) and at the Deep Fluorescence Maximum (DFM, 12–55 m) at eight representative stations of the three areas. The average viral lytic production ranged from 1.0 ± 0.3 × 107 viruses ml−1 d−1 in the Bellingshausen Sea to1.3 ± 0.7 × 107 viruses ml−1 d−1 in the Bransfield Strait, while lysogeny, when detectable, recorded the lowest value in the Bellingshausen Sea (0.05 ± 0.05 × 107 viruses ml−1 d−1) and the highest in the Weddell Sea (4.3 ± 3.5 × 107 viruses ml−1 d−1). Average mortality rates due to viruses ranged from 9.7 ± 6.1 × 104 cells ml−1 d−1 in the Weddell Sea to 14.3 ± 4.0 × 104 cells ml−1 d−1 in the Bellingshausen Sea, and were higher than averaged grazing rates in the Weddell Sea (5.9 ± 1.1 × 104 cells ml−1 d−1) and in the Bellingshausen Sea (6.8 ± 0.9 × 104 cells ml−1 d−1). The highest impact on prokaryotes by viruses and main differences between viral and protists activities were observed in surface samples: 17.8 ± 6.8 × 104 cells ml−1 d−1 and 6.5 ± 3.9 × 104 cells ml−1 d−1 in the Weddell Sea; 22.1 ± 9.6 × 104 cells ml−1 d−1 and 11.6 ± 1.4 × 104 cells ml−1 d−1 in the Bransfield Strait; and 16.1 ± 5.7 × 104 cells ml−1 d−1 and 7.9 ± 2.6 × 104 cells ml−1 d−1 in the Bellingshausen Sea, respectively. Furthermore, the rate of lysed cells and PHP showed higher sensitivity to

The Viral tagging technique is a promising method for detecting virus-host interactions both in culture and in natural samples. We have applied this technique to Pseudoalteromonas-Phage models getting successful results. We monitored the attachment process of different viral-host systems using flow cytometry. Our preliminary results suggest that there are two kinds of infections: the fast attaching viruses that infect bacteria in about 30 minutes, and the slow attaching viruses that infect bacteria in about 2 hours. After this period of time the percentage of labeled bacteria decreased suggesting that lysis occurs. Lysis was confirmed by spectrophotometry. We have observed that to get reliable outcomes with this technique it is important to control parameters as temperature, bacterial generation times, and dyes incubation time among others. The final objective is to use this technique for detecting the interaction between viruses and hosts in nature during annual cycles, allowing us to know how viral infections respond to biological, physical and chemical changes

Samples from the MALASPINA circumnavigation expedition (2010‐2011) were collected to study the influence of microbial abundances in the distribution of the fluorescent dissolved organic matter (FDOM). The FDOM excitation‐emission matrix (EEM) data, obtained using a Fluoromax‐4 spectrofluorimeter, were examined with Parallel Factor Analysis (PARAFAC). The PARAFAC analysis identified four components, two of them associated with humic‐like substances (C1 and C2) and the other two with protein‐like compounds (C3 and C4). In the specific context of this study, we will only refer to the protein‐like components: C3 corresponds to classic peak‐T, which is related to the essential aminoacid tryptophan (excitation‐emission 290/340 nm); and C4, associated to classic peak‐B, is related to the non‐essential aminoacid tyrosine (excitation‐emission 270/310 nm). We study the relationships between these two FDOM compounds and viruses and bacteria abundances compiled in the Malaspina database which includes values from 5 different oceanic basins (North Atlantic, South Atlantic, Indian, North Pacific and South Pacific). Samples were collected from 0 m to 4000 m depth, distinguishing three different layers (epipelagic 0‐200 m, mesopelagic 200‐1000 m, and bathypelagic 1000‐4000 m). Our aim was to determine if the dynamics of these FDOM components followed the evolution of the bacteria and/or viruses abundances. To achieve this objective we applied residual analyses to exclude the variability due to physicochemical parameters (temperature and salinity). When the whole database was considered, these parameters accounted for a high percentage (~60%) of both virus and prokaryotic variability. The residual analyses shown, in general, that the C3 component was significantly correlated to virus abundance. In contrast, only a weak C3‐prokaryotic abundance relationship was found in the mesopelagic zone of the North Pacific basin. On the other hand, C4 shown, in general, no clear relationship nei