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Background Palliative care has become a key medical field worldwide. Although research relating to adult palliative care is well-established, less is known about children's palliative care (CPC). Therefore, this study investigated the knowledge, attitude and behavior of pediatric healthcare workers (PHWs) regarding CPC and analyzed the influencing factors for the implementation and development of CPC. Methods A cross-sectional survey of 407 PHWs was carried out in a Chinese province from November 2021 to April 2022. The questionnaire consisted of two parts: a general information form and questions on the knowledge, attitude and behavior of PHWs about CPC. Data were analyzed using t-test, ANOVA and multiple regression analysis. Results A total of 412 questionnaires were distributed in this survey, of which 407 were valid, with a valid return rate of 98.79%. The total score of the PHWs’ knowledge, attitude and behavior about CPC was 69.98, which was at a moderate level. The most important influencing factors were working years, highest education, professional title, job position, marital status, religion, grade of hospital (I, II or III), type of medical institution, experience of caring for a terminally ill child/kinsfolk and total hours of CPC education and training received. Conclusions In this study, PHWs in a Chinese province had the lowest scores on the knowledge dimension of CPC, with moderate attitude and behavior and various influencing factors. In addition to professional title, highest education and working years, it is also worth noting that the type of medical institution and marital status also affected the score. Continuing education and training of PHWs in CPC should be emphasized by the administrators of relevant colleges and medical institutions. Future research should start with the above-mentioned influencing factors and focus on setting up targeted training courses and evaluating the post-training effects.

The increasing-volume release of micropollutants into natural surface waters has raised great concern due to their environmental accumulation. Persisting micropollutants can impact multiple generations of organisms, but their microbially-mediated degradation and their influence on community assembly remain understudied. Here, freshwater microbes were treated with several common micropollutants, alone or in combination, and then transferred every 5 days to fresh medium containing the same micropollutants to mimic the repeated exposure of microbes. Metabarcoding of 16S rRNA gene makers was chosen to study the succession of bacterial assemblages following micropollutant exposure. The removal rates of micropollutants were then measured to assess degradation capacity of the associated communities. The degradation of micropollutants did not accelerate over time but altered the microbial community composition. Community assembly was dominated by stochastic processes during early exposure, via random community changes and emergence of seedbanks, and deterministic processes later in the exposure, via advanced community succession. Early exposure stages were characterized by the presence of sensitive microorganisms such as Actinobacteria and Planctomycetes, which were then replaced by more tolerant bacteria such as Bacteroidetes and Gammaproteobacteria. Our findings have important implication for ecological feedback between microbe-micropollutants under anthropogenic climate change scenarios.

The high-volume release of micropollutants into natural surface waters has raised concern due to their environmental accumulation. Persisting micropollutants can impact multiple generations of organisms via press disturbances, but their microbially-mediated degradation and the influence on community assembly remain understudied. Here, freshwater microbial communities in microcosms were treated with four common micropollutants, alone or in combination, and then transferred in stages to fresh medium containing the same level of micropollutants to mimic the recurrent exposure of microbes under environmentally relevant conditions. Our results showed that the degradation of micropollutants was closely linked to the community succession, and that recurrent exposure to micropollutants enhanced the degradation capacity. The partitioning analysis of ecological processes revealed that community assembly was dominated by stochastic processes during early exposure, via random community changes, and by deterministic processes later in the exposure. Analyzing individual taxa abundances over time revealed two distinct bacterial responses, in which a larger proportion of sensitive than tolerant taxa was present in the disturbed communities, and the abundances of the most sensitive taxa were significantly associated with micropollutant degradation. This study clearly showed that microbial communities are generally vulnerable to persisting micropollutants in aquatic environments, which has important implications for pollution management, especially regarding microbial dynamics and ecosystem functioning in micropollutant removal.

This study investigated the microbial structure in the surface seawater from five coastal sites around Xiamen Island, China, over four seasons to evaluate seasonal environmental fluctuations impact on them. This subtropical island is characterized by long, hot, humid summers, and short, mild, dry winters. All sites were dominated by Proteobacteria, Bacteroidetes, Cyanobacteria, and Firmicutes; microbial community composition was similar across four seasons. However, larger proportions of Gammaproteobacteria and Bacillus were observed during the summer than during any other season. The high ratio of Bacillus, Bacteroidetes, and Clostridia richness to Alphaproteobacteria richness in the summer, suggested that the sites we tested were heavily affected by waste water to other seasons. Correlation-based network analyses among the bacterial species and environmental variables indicated important connections between physiochemical variables and specific taxonomic groups. Collectively, our results suggested that seasonal shifts and wastewater pollution together shape the structures of the microbial communities around Xiamen Island.

Author(s): Xia, X; Wang, Y; Yang, Y; Luo, T; Van Nostrand, JD; Zhou, J; Jiao, N; Zhang, R | Abstract: Ocean acidification (OA), a consequence of increased global carbon dioxide (CO2) emissions, is considered a major threat to marine ecosystems. Its effects on bacterioplankton activity, diversity, and community composition have received considerable attention. However, the direct impact of OA on heterotrophic bacterioplankton is often masked by the significant response of phytoplankton due to the close coupling of heterotrophic bacterioplankton and autotrophs. Here we investigated the responses of a heterotrophic bacterioplankton assemblage to high pCO2 (790-ppm) treatment in warm tropical western Pacific waters by conducting a microcosm experiment in dark for 12ndays. Heterotrophic bacterioplankton abundance and production were enhanced by OA over the first 6ndays of incubation, while the diversity and species richness were negatively affected. Bacterioplankton community composition in the high pCO2 treatment changed faster than that in the control. The molecular ecological network analysis showed that the elevated CO2 changed the overall connections among the bacterial community and resulted in a simple network under high CO2 condition. Species-specific responses to OA were observed and could be attributed to the different life strategies and to the ability of a given species to adapt to environmental conditions. In addition, high-throughput functional gene array analysis revealed that genes related to carbon and nitrogen cycling were positively affected by acidification. Together, our findings suggest that OA has direct effects on heterotrophic bacterioplankton in a low-latitude warm ocean and may therefore affect global biogeochemical cycles.

In this work, the microalloying approach was adopted to improve the mechanical properties of Mg-6Zn-0.5Zr alloy by co-addition of trace Cu and Ce elements. The results showed that the grain size of the Mg-6Zn-0.5Zr-0.5Cu-0.5Ce alloy was refined, and MgZnCu and Mg-Zn-Ce phases formed by the microalloying of Cu and Ce. In addition, high-density nano-scale precipitates were found in the matrix after extrusion. The alloy with Cu and Ce addition showed a basal texture with a stronger texture intensity. The yield strength, ultimate tensile strength and elongation of the as-extruded Mg-6Zn-0.5Zr-0.5Cu-0.5Ce alloy were 304 MPa, 345 MPa and 20.0%, respectively. This work demonstrated a close microstructure-strength relationship in which the refined grain size and abundant nano-scale precipitates led to an increase in the tensile yield strength of approximately 59 MPa compared with that of the Cu and Ce free alloy.

The China Seas include the South China Sea, East China Sea, Yellow Sea, and Bohai Sea. Located off the Northwestern Pacific margin, covering 4700000 km2 from tropical to northern temperate zones, and including a variety of continental margins/basins and depths, the China Seas provide typical cases for carbon budget studies. The South China Sea being a deep basin and part of the Western Pacific Warm Pool is characterized by oceanic features; the East China Sea with a wide continental shelf, enormous terrestrial discharges and open margins to the West Pacific, is featured by strong cross-shelf materials transport; the Yellow Sea is featured by the confluence of cold and warm waters; and the Bohai Sea is a shallow semi-closed gulf with strong impacts of human activities. Three large rivers, the Yangtze River, Yellow River, and Pearl River, flow into the East China Sea, the Bohai Sea, and the South China Sea, respectively. The Kuroshio Current at the outer margin of the Chinese continental shelf is one of the two major western boundary currents of the world oceans and its strength and position directly affect the regional climate of China. These characteristics make the China Seas a typical case of marginal seas to study carbon storage and fluxes. This paper systematically analyzes the literature data on the carbon pools and fluxes of the Bohai Sea, Yellow Sea, East China Sea, and South China Sea, including different interfaces (land-sea, sea-air, sediment-water, and marginal sea-open ocean) and different ecosystems (mangroves, wetland, seagrass beds, macroalgae mariculture, coral reefs, euphotic zones, and water column). Among the four seas, the Bohai Sea and South China Sea are acting as CO2 sources, releasing about 0.22 and 13.86– 33.60 Tg C yr−1 into the atmosphere, respectively, whereas the Yellow Sea and East China Sea are acting as carbon sinks, absorbing about 1.15 and 6.92 –23.30 Tg C yr−1 of atmospheric CO2, respectively. Overall, if only the CO2 exchange at the sea-air interface is considered, the Chinese marginal seas appear to be a source of atmospheric CO2, with a net release of 6.01 –9.33 Tg C yr−1 , mainly from the inputs of rivers and adjacent oceans. The riverine dissolved inorganic carbon(DIC) input into the Bohai Sea and Yellow Sea, East China Sea, and South China Sea are 5.04, 14.60, and 40.14 Tg C yr−1 , respectively. The DIC input from adjacent oceans is as high as 144.81 Tg C yr−1 , significantly exceeding the carbon released from the seas to the atmosphere. In terms of output, the depositional fluxes of organic carbon in the Bohai Sea, Yellow Sea, East China Sea, and South China Sea are 2.00, 3.60, 7.40, and 5.92 Tg C yr−1 , respectively. The fluxes of organic carbon from the East China Sea and South China Sea to the adjacent oceans are 15.25–36.70 and 43.93 Tg C yr−1 , respectively. The annual carbon storage of mangroves, wetlands, and seagrass in Chinese coastal waters is 0.36 –1.75 Tg C yr−1 , with a dissolved organic carbon (DOC) output from seagrass beds of up to 0.59 Tg C yr−1 . Removable organic carbon flux by Chinese macroalgae mariculture account for 0.68 Tg C yr−1 and the associated POC depositional and DOC releasing fluxes are 0.14 and 0.82 Tg C yr−1 , respectively. Thus, in total, the annual output of organic carbon, which is mainly DOC, in the China Seas is 81.72 –104.56 Tg C yr−1 . The DOC efflux from the East China Sea to the adjacent oceans is 15.00 –35.00 Tg C yr−1 . The DOC efflux from the South China Sea is 31.39 Tg C yr−1 . Although the marginal China Seas seem to be a source of atmospheric CO2 based on the CO2 flux at the sea-air interface, the combined effects of the riverine input in the area, oceanic input, depositional export, and microbial carbon pump (DOC conversion and output) indicate that the China Seas represent an important carbon storage area.

In this study, an approach is proposed to improve the microstructure and mechanical properties of Mg-4Zn-0.5Zr alloy by combining trace Cu and rare earth Ce addition. The results showed that Cu and...

Viral abundance in deep-sea environments is high. However, the biological, ecological and biogeochemical roles of viruses in the deep sea are under debate. In the present study, microcosm incubations of deep-sea bacterioplankton (2,000 m deep) with normal and reduced pressure of viral lysis were conducted in the western Pacific Ocean. We observed a negative effect of viruses on prokaryotic abundance, indicating the top-down control of bacterioplankton by virioplankton in the deep-sea. The decreased bacterial diversity and a different bacterial community structure with diluted viruses indicate that viruses are sustaining a diverse microbial community in deep-sea environments. Network analysis showed that relieving viral pressure decreased the complexity and clustering coefficients but increased the proportion of positive correlations for the potentially active bacterial community, which suggests that viruses impact deep-sea bacterioplankton interactions. Our study provides experimental evidences of the crucial role of viruses in microbial ecology and biogeochemistry in deep-sea ecosystems., Rui Zhang et al. demonstrate that reduced viral pressure decreases the diversity of deep-sea bacterioplankton in the western Pacific Ocean. This study suggests that viruses sustain a diverse microbial community in deep-sea environments.

The influence of temperature conditions on the grain refinement of pure Cu solidified with low-voltage pulsed magnetic field (LVPMF) was investigated. With the pouring temperature (Tp) and mould temperature (Tm) increasing, the solidified microstructure of pure Cu was gradually changed from fine equiaxed grains to coarse columnar grains and then to the mixed structure of coarse equiaxed grains and columnar grains. Little change was observed from the microstructure of pure Cu solidified with and without LVPMF for the low Tp and Tm. But for the high Tp and Tm, applying LVPFM remarkably reduced the coarse columnar grains and obtained fine equiaxed grains. The grain refinement by LVPFM is considered to be caused by the electromagnetic flow. The smaller cooling rate resulted by higher Tp and Tm offers much acting time for LVPMF and thus better grain refinement can be achieved.

The bathypelagic zone is a large, dark, cold, high-pressure environment that undergoes extensive material and energy exchanges with the upper ocean and the deep biosphere. Viruses are important parts of the deep ocean, and transportation of surface viruses has been considered as an important source of deep-sea viruses. However, limited information is available about the activity and decay of surface viruses in the deep-sea ecosystem. Therefore, this study investigated the stability of representative viral isolates of three morphological types with different sizes infecting autotrophic and heterotrophic bacteria by incubation in the dark under high hydrostatic pressure (HHP) of 30 MPa (corresponding to the pressure at a depth of about 3000 m) and 4 °C for two years. Cyanophage S-CBP1 and two roseophages, RDCBΦ1 and vB_DshS-R4C, were able to infect their hosts after long-term incubation under HHP. However, cyanophages S-CBWM1 and S-SCSM1, as well as roseophages RDCBΦ3 and vB_DshP-R2C, decayed and/or inactivated completely. The sensitivity of viral isolates to HHP might be related to their morphological characteristics, especially their capsid sizes. In addition, HHP treatment of environmental viral populations showed 92.2% reduction of low-fluorescence viruses and total loss of high-fluorescence viruses. The first experimental evidence from this study showed a large variability in the pressure effects on the stability and infectivity of different viruses and suggests that viruses isolated from the ocean's surface may survive under deep-sea conditions.

Picophytoplankton are acknowledged to contribute significantly to primary production in the ocean while now the method to measure primary production of picophytoplankton at large scales is not yet well established. Although the traditional 14C method and new technologies based on the use of stable isotopes (e.g. 13C) can be employed to accurately measure in situ primary production of picophytoplankton, the time-consuming and labor-intensive shortage of these methods constrain their application in a survey on large spatiotemporal scales. To overcome this shortage, a modified carbon-based ocean productivity model (CbPM) is proposed for estimating the primary production of picophytoplankton whose principle is based on the group-specific abundance, cellular carbon conversion factor and temperature derived growth rate of picophytoplankton. Comparative analysis showed that the estimated primary production of picophytoplankton using CbPM method is significantly and positively related (r2= 0.53, P

As the most abundant biological entities in the ocean, viruses influence host mortality and nutrient recycling mainly through lytic infection. Yet, the ecological characteristics of virioplankton and viral impacts on host mortality and biogeochemical cycling in the deep sea are largely unknown. In the present study, viral abundance and lytic infection were investigated throughout the water column in the western Pacific Ocean. Both the prokaryotic and viral abundance and production showed a significantly decreasing trend from epipelagic to meso- and bathypelagic waters. Viral abundance decreased from 0.36–1.05 × 1010 particles L−1 to 0.43–0.80 × 109 particles L−1, while the virus : prokaryote ratio varied from 7.21 to 16.23 to 2.45–23.40, at the surface and 2000 m, respectively. Lytic viral production rates in surface and 2000 m waters were, on average, 1.03 × 1010 L−1 day−1 and 5.74 × 108 L−1 day−1. Relatively high percentages of prokaryotic cells lysed by viruses at 1000 and 2000 m were observed, suggesting a significant contribution of viruses to prokaryotic mortality in the deep ocean. The carbon released by viral lysis in deep western Pacific Ocean waters was from 0.03 to 2.32 μg C L−1 day−1. Our findings demonstrated a highly dynamic and active viral population in these deep waters and suggested that virioplankton play an important role in the microbial loop and subsequently biogeochemical cycling in deep oceans.

Prochlorococcus, the smallest but most abundant marine primary producer, plays an important role in carbon cycling of the global ocean. As a phototroph, Prochlorococcus is thought to be confined to the euphotic zone, with commonly observed maximum depths of ~ 150–200 m, but here we show for the first time the substantial presence of Prochlorococcus populations in the dark ocean ("deep Prochlorococcus" hereafter). Intensive studies at the Luzon Strait in the western Pacific Ocean show that the deep Prochlorococcus populations are exported from the euphotic zone. Multiple physical processes including internal solitary waves could be responsible for the transportation. These findings reveal a novel mechanism for picoplankton carbon export other than the known mechanisms such as sinking of phytodetritus and aggregates or grazing-mediated transportation.

National Natural Science Foundation of China [41171050, 40871045, 40810019001, 40830743, 40874033]; Ministry of Science and Technology of the People's Republic of China [2012CB956101]; Chinese Academy of Science [KZCX2-YW-JC106]

Mg alloy foams with different cell sizes, fixed porosity, and uniform structure were prepared by direct foaming method. The microstructure characteristics and quasi-static compressive behaviors of the foams were investigated. The results showed that the pores in the foams were polygon with the porosity of 87%. Decreasing the cell size is beneficial to eliminating the big cell edges in the foams. The foams with smaller average cell size possess better deformation stability when being compressed. Decrease of the average cell size improves the strength of the foams by sharing the load with more and smaller cells; however too small average cell size can impair the strength because no enough metals hold the integrity of the new cell walls. The densification strain hardly changes with the varying average cell size and fixed porosity.

The corrosion resistance property and the corrosion evolution of as-cast AZ91 alloy with rare earth Y addition are investigated by using immersion tests, electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS). The results show that the proper amount of Y in the alloys can improve the corrosion resistance of AZ91 alloys effectively. With the increment of Y, the corrosion rate of the modified AZ91 alloys by Y addition was markedly less than that of AZ91 alloy. The corrosion rate of AZ91 alloy with 0.3 wt.% Y was the slightest, but further addition of Y content over 0.3 wt.% make the corrosion heavier. The XPS analysis suggests that the compound film of AZ91 alloy with 0.3 wt.% Y is mainly composed of Mg(OH)(2) and MgCO(3) without any Al(OH)(3) and Al(2)O(3), in addition, Y(2)O(3) phase is found in the compound film of AZ91 alloy with 0.3 wt.% Y, which benefits to stabilize the surface film. (C) 2011 Elsevier Ltd. All rights reserved.

The biological pump is a process whereby CO(2) in the upper ocean is fixed by primary producers and transported to the deep ocean as sinking biogenic particles or as dissolved organic matter. The fate of most of this exported material is remineralization to CO(2), which accumulates in deep waters until it is eventually ventilated again at the sea surface. However, a proportion of the fixed carbon is not mineralized but is instead stored for millennia as recalcitrant dissolved organic matter. The processes and mechanisms involved in the generation of this large carbon reservoir are poorly understood. Here, we propose the microbial carbon pump as a conceptual framework to address this important, multifaceted biogeochemical problem.

The fatigue deformation behavior of as-extruded AM30 magnesium alloy has been investigated under different strain amplitudes in this paper, and the microstructure and fractograph during the cyclic deformation have been analyzed by use of the optical microscope (OM) and the scanning electronic microscope (SEM). The results show that there are many {1 0 –1 2} twins in the fatigue specimens of the extruded AM30 alloy, and with the increase of total strain amplitude, the twins become coarser and longer. Otherwise, there are many twin bands composed of many tiny lenticular type twins ({1 0 –1 2}〈1 0 –1 1〉 twin) near the fatigue fracture, which become more with increase of total strain amplitude.

The influence of different contents of rare earth Y on the corrosion resistance of AZ91 alloy was investigated by the salt spray test and electrochemical measurements. It was found that the proper amount of Y was effective on improving the corrosion resistance of AZ91 alloy. The optimal modification effect was obtained when the Y content in the alloys was 0.3 wt.%. However, with the increase of rare earth Y, the corrosion rate became bigger slightly, and further addition of Y content over 0.3 wt.% resulted in the increment of the corrosion rate. It is suggested that the excessive rare earth Y can reduce the corrosion resistance of AZ91 alloy.

The bacterial diversity and abundance in the snow of East Rongbuk glacier, Mt. Everest were examined through 16S rRNA gene clone library and flow cytometry approaches. In total, 35 16S rRNA gene sequences were obtained, which belong to α, β, γ-Proteobacteria, Actinobacteria, Firmicutes, CFB, Cyanobacteria, Eukaryotic chloroplast, and TM7 candidate phylum respectively. γ-Proteobacteria was the dominant bacterial group in this region, while the genera Acinetobacter and Leclercia were dominant on the genus level. The community structure varied seasonally. The bacterial abundance in summer snow was higher than that in winter. Moreover, the snow bacterial community structures in both seasons were diverse, with not only common species but season-specific species. The common species most likely originated from the Tibet Plateau. Bacteria in summer snow are affiliated with marine environment, whereas bacteria in winter snow are closely related to more diverse environments and show the feature of resistance to cold. Seasonal variations of abundance and bacterial diversity were most probably due to the seasonal characteristics of climate and atmospheric circulation in Mt. Everest.

Seasonal investigation of virus dynamics by flow cytometry was conducted in the Yangtze river estuarine area in April, August, November 2002 and February 2003, and a supplemental investigation in the inner estuary and downstream of the river was conducted in October 2005. The majority of the total viral abundance was bacteriophage and only 5.4% of the total was algal virus. Total viral abundance varied with season and location, ranging from 6.75×105–1.68×107 particles/ml, and the virus:bacterium ratio (VBR) ranged from 1.52 to 72.02 with a mean of 8.7. In the present study, viral abundance peaked in both the summer and the winter, unlike the typical seasonal pattern reported in the literature, in which viral abundance peaks in the summer when bacterial hosts are also at their most abundant. However, the driving forces for the two peaks reported here were totally different, the summer viral abundance peak coupled with the development of bacterial hosts which were controlled largely by temperature year-round and by trophic state occasionally, while the winter one seemed to be multi-factor controlled. The host-phage interaction was no longer predominant in control of the winter viral abundance as bacterial abundance was lowest in this season. The winter low temperature would help maintain a high viral abundance as high temperatures might increase viral inactivation and viral decay; the VBR peak values actually occurred in the winter. More importantly, the high virus-containing freshwater discharge in winter due to a higher proportion of anthropogenic sewage relative to low natural flooding in winter run-off, turned out to be the first factor contributing to the high winter viral abundance and VBR values. In addition, the variation of intrusion of warm and relatively oligotrophic water from oceanic currents played a role alternating the distribution patterns of temperature, salinity and trophic conditions and consequently the distribution patterns of virus and bacteria seasonally and spatially. Dynamics of virus in the Yangtze river estuarine area is thus characterized by distinct seasonal and spatial variations due to natural forcing and by pronounced alternation of the regular patterns due to anthropogenic impacts.

Proliferating cell nuclear antigen (PCNA) was detected in Prorocentrum donghaiense Lu and Dunaliella salina Teodoresco by enhanced chemiluminescence techniques with one mono-antibody. The observed band detected on western blots of P. donghaiense and D. salina had a molecular weight of 36‐33 kDa rather than a PCNA-like protein with a size of 55 kDa reported in the dinoflagellates Crypthecodinium cohnii Biecheler and Gymnodinium catenatum Brav. The abundance of PCNA proteins was growth-stage dependent. Whole-cell immunoflurescence labeling showed that the PCNA antibody specifically stained the target proteins in P. donghaiense and D. salina, and PCNA is only present in the nucleus during the cell cycle. Synchronized cells of P. donghaiense show a cell cycle specific expression pattern with the highest expression in S phase and little expression in the G1 and G2/M phases. The results demonstrated that the PCNA-like proteins could be a marker for the estimation of marine phytoplankton growth rates. The different sizes of the PCNA-like proteins observed in dinoflagellates could be related to the variety of dinoflagellate chromosomal structure.

A simplified protocol for determination of bacterial membrane potential (MP) by flow cytometry with 3,3'-dihexyloxacarbocyanine iodide (DiOC 6 (3)) as the MP probe was established, and was applied to an aerobic anoxygenic phototrophic bacterium (AAPB strain, Roseobacter clade) with an Escherichia coli strain as a reference. It was shown to be capable of precise indication of the physiological states of the cells as well as cellular responses to environmental factors. Based on the experimental results, a MP curve model was proposed for characterization of species-specific fea- tures, which offers parameters including the maximum MP of the curve (MP max ), the time to reach the MP max (T max ), the slope of the exponential phase of the MP curve (K MP ), and the minimum (threshold) concentration of a particular substrate required for the organism to reach its MP max (S max ). These parameters are functions of substrates and incubation conditions for a single species, and can be used for comparison between different species under the same conditions. The MP max , T max , and K MP of the AAPB strain were quite different form those of the E. coli strain, and the AAPB strain was shown to be less sensitive to temperature and pH changes than the E. coli strain.

Arrieta et al . (Reports, 17 April 2015, p. 331) propose that low concentrations of labile dissolved organic carbon (DOC) preclude prokaryotic consumption of a substantial fraction of DOC in the deep ocean and that this dilution acts as an alternative mechanism to recalcitrance for long-term DOC storage. Here, we show that the authors’ data do not support their claims.

A prophage vB_CibM-P1 was induced by mitomycin C from the epipelagic strain Citromicrobium bathyomarinum JL354, a member of the alpha-IV subcluster of marine aerobic anoxygenic phototrophic bacteria (AAPB). The induced bacteriophage vB_CibM-P1 had Myoviridae-like morphology and polyhedral heads (approximately capsid 60-100 nm) with tail fibers. The vB_CibM-P1 genome is ~38 kb in size, with 66.0% GC content. The genome contains 58 proposed open reading frames that are involved in integration, DNA packaging, morphogenesis and bacterial lysis. VB_CibM-P1 is a temperate phage that can be directly induced in hosts. In response to mitomycin C induction, virus-like particles can increase to 7 × 10(9) per ml, while host cells decrease an order of magnitude. The vB_CibM-P1 bacteriophage is the first inducible prophage from AAPB.

International audience; This paper reviews progress on understanding biological carbon sequestration in the ocean with special reference to the microbial formation and transformation of recal-citrant dissolved organic carbon (RDOC), the microbial carbon pump (MCP). We propose that RDOC is a concept with a wide continuum of recalcitrance. Most RDOC compounds maintain their levels of recalcitrance only in a specific environmental context (RDOC t). The ocean RDOC pool also contains compounds that may be inaccessible to microbes due to their extremely low concentration (RDOC c). This differentiation allows us to appreciate the linkage between microbial source and RDOC composition on a range of temporal and spatial scales. Analyses of biomarkers and isotopic records show intensive MCP processes in the Proterozoic oceans when the MCP could have played a significant role in regulating climate. Understanding the dynamics of the MCP in conjunction with the better constrained biological pump (BP) over geological timescales could help to predict future climate trends. Integration of the MCP and the BP will require new research approaches and opportunities. Major goals include understanding the interactions between particulate organic carbon (POC) and RDOC that contribute to sequestration efficiency, and the concurrent determination of the chemical composition of organic carbon, microbial community composition and enzymatic activity. Molecular biomarkers and isotopic tracers should be employed to link water column processes Published by Copernicus Publications on behalf of the European Geosciences Union. 5286 N. Jiao et al.: Mechanisms of microbial carbon sequestration in the ocean to sediment records, as well as to link present-day observations to paleo-evolution. Ecosystem models need to be developed based on empirical relationships derived from bioassay experiments and field investigations in order to predict the dynamics of carbon cycling along the stability continuum of POC and RDOC under potential global change scenarios. We propose that inorganic nutrient input to coastal waters may reduce the capacity for carbon sequestration as RDOC. The nutrient regime enabling maximum carbon storage from combined POC flux and RDOC formation should therefore be sought.

Despite the fact that marine viruses have been increasingly studied in the last decade, there is little information on viral abundance and distribution on a global scale. In this study, we report on a global-scale survey covering the Pacific, Atlantic, and Indian Oceans on viral distribution using flow cytometry. Viruses were stained with the SYBR Green I, which targets only dsDNA viruses. The average viral abundance was 1.10 +/- 0.73x10(7) ml(-1) in global surface oceans and decreased from the areas with high chlorophyll concentration (on average, 1.47 +/- 0.78x10(7) ml(-1)) to the oligotrophic subtropical gyres (on average, 6.34 +/- 2.18x10(6) ml(-1)). On a large-spatial-scale, viruses displayed significant relationships with both heterotrophic and autotrophic picoplankton abundance, suggesting that viral distribution is dependent on their host cell abundance. Our study provided a basin scale pattern of marine viral distributions and their relationship with major host cells, indicating that viruses play a significant role in the global marine ecosystem.

The origin of phytohormones is poorly understood, and their physiological roles in microalgae remain elusive. Genome comparison of photosynthetic autotrophic eukaryotes has revealed that the biosynthetic pathways of abscisic acid (ABA) and cytokinins (CKs) emerged in unicellular algae. While ABA and CK degradation mechanisms emerged broadly in algal lineages, complete vascular plant-type conjugation pathways emerged prior to the rise of Streptophyta. In microalgae, a complete set of proteins from the canonical ABA and CK sensing and signaling pathways is not essential, but individual components are present, suggesting stepwise recruitment of phytohormone signaling components. In the oleaginous eustigmatophyte Nannochloropsis oceanica IMET1, UHPLC-MS/MS detected a wide array of plant hormones, despite a phytohormone profile that is very distinct from that of flowering plants. Time-series transcriptional analysis during nitrogen depletion revealed activation of the ABA biosynthetic pathway and antagonistic transcription of CK biosynthetic genes. Correspondingly, the ABA level increases while the dominant bioactive CK forms decrease. Moreover, exogenous CKs stimulate cell-cycle progression while exogenous ABA acts as both an algal growth repressor and a positive regulator in response to stresses. The presence of such functional flowering plant-like phytohormone signaling systems in Nannochloropsis sp. suggests a much earlier origin of phytohormone biosynthesis and degradation than previously believed, and supports the presence in microalgae of as yet unknown conjugation and sensing/signaling systems that may be exploited for microalgal feedstock development.

Virio- and picoplankton mediate important biogeochemical processes and the environmental factors that regulate their dynamics, and the virus-host interactions are incompletely known, especially in the deep sea. Here we report on their distributions and relationships with environmental factors at 21 stations covering a latitudinal range (2-23 degrees N) in the Western Pacific Ocean. This region is characterized by a complex western boundary current system. Synechococcus, autotrophic picoeukaryotes, heterotrophic prokaryotes and virus-like particles (VLPs) were high (< 2.4 Chi 10(2)-6.3 Chi 10(4), < 34-2.8 Chi 10(3), 3.9 Chi 10(4)-1.3 Chi 10(6) cellsmL(-1) and 5.1 Chi 10(5)-2.7 Chi 10(7) mL(-1), respectively), and Prochlorococcus were low (< 2.3 Chi 10(2)-1.0 Chi 10(5) cellsmL(-1)) in the Luzon Strait and the four most southerly stations, where upwelling occurs. Covariations in the abundances of VLPs with heterotrophic and autotrophic picoplankton, and their correlation (i.e. r(2) = 0.63 and 0.52, respectively) suggested a strong host dependence in the epi-and mesopelagic zones. In the bathypelagic zone, only abiotic factors significantly influenced VLPs abundance variation ( r(2) = 0.12). This study shows that the dynamics of virio- and picoplankton in this Western Pacific are controlled by suite of complex and depth-dependent relationship among physical and biological factors that in turn link the physical hydrography of the western boundary current system with microbial-mediated biogeochemical processes.

N. Jiao1, C. Robinson2, F. Azam3, H. Thomas4, F. Baltar5, H. Dang1, N. J. Hardman-Mountford6, M. Johnson2, D. L. Kirchman7, B. P. Koch8, L. Legendre9,10, C. Li11, J. Liu1, T. Luo1, Y.-W. Luo1, A. Mitra12, A. Romanou13, K. Tang1, X. Wang14, C. Zhang15, and R. Zhang1 1State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China 2School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK 3Scripps Institution of Oceanography, UCSD, La Jolla, CA 920193, USA 4Dalhousie University, Halifax, Nova Scotia, Canada 5Department of Marine Science, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand 6CSIRO Marine and Atmospheric Research, Floreat, WA 6014, Australia 7School of Marine Science and Policy, University of Delaware, DE 19958, USA 8Alfred-Wegener-Institut Helmholtz-Zentrum fur Polarund Meeresforschung, 27570 Bremerhaven, Germany 9Sorbonne Universites, UPMC Univ. Paris 06, UMR7093, Laboratoire d’Oceanographie de Villefranche, 06230 Villefranche-sur-Mer, France 10CNRS, UMR7093, Laboratoire d’Oceanographie de Villefranche, 06230 Villefranche-sur-Mer, France 11State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China 12Centre for Sustainable Aquatic Research, Swansea University, Swansea, UK 13Dept. of Applied Physics and Applied Math., Columbia University and NASA-Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA 14South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China 15Tongji University, Shanghai, China