The microbial carbon pump and climate change.

The ocean has been a regulator of climate change throughout the history of Earth. One key mechanism is the mediation of the carbon reservoir by refractory dissolved organic carbon (RDOC), which can either be stored in the water column for centuries or released back into the atmosphere as CO2 depending on the conditions. The RDOC is produced through a myriad of microbial metabolic and ecological processes known as the microbial carbon pump (MCP). Here, we review recent research advances in processes related to the MCP, including the distribution patterns and molecular composition of RDOC, links between the complexity of RDOC compounds and microbial diversity, MCP-driven carbon cycles across time and space, and responses of the MCP to a changing climate. We identify knowledge gaps and future research directions in the role of the MCP, particularly as a key component in integrated approaches combining the mechanisms of the biological and abiotic carbon pumps for ocean negative carbon emissions.

Genomic insights into the adaptation of Synechococcus to the coastal environment on Xiamen.

Synechococcus are widely distributed in the global ocean, from the pelagic zone to coastal waters. However, little is known about Synechococcus in coastal seawater due to limitations in isolation and culture conditions. In this study, a combination of metagenomic sequencing technology, flow cytometry sorting, and multiple displacement amplification was used to investigate Synechococcus in the coastal seawater of Xiamen Island. The results revealed 18 clades of Synechococcus and diverse metabolic genes that appear to contribute to their adaptation to the coastal environment. Intriguingly, some metabolic genes related to the metabolism of carbohydrates, energy, nucleotides, and amino acids were found in 89 prophage regions that were detected in 16,258 Synechococcus sequences. The detected metabolic genes can enable prophages to contribute to the adaptation of Synechococcus hosts to the coastal marine environment. The detection of prophages also suggests that the cyanophages have infected Synechococcus. On the other hand, the identification of 773 genes associated with antiviral defense systems indicates that Synechococcus in Xiamen have evolved genetic traits in response to cyanophage infection. Studying the community diversity and functional genes of Synechococcus provides insights into their role in environmental adaptation and marine ecosystems.

Virus-Host Interactions Drive Contrasting Bacterial Diel Dynamics in the Ocean.

Marine organisms perform a sea of diel rhythmicity. Planktonic diel dynamics have been shown to be driven by light, energy resources, circadian rhythms, and the coordinated coupling of photoautotrophs and heterotrophic bacterioplankton. Here, we explore the diel fluctuation of viral production and decay and their impact on the total and active bacterial community in the coastal and open seawaters of the South China Sea. The results showed that the night-production diel pattern of lytic viral production was concurrent with the lower viral decay at night, contributing to the accumulation of the viral population size during the night for surface waters. The diel variations in bacterial activity, community composition, and diversity were found highly affected by viral dynamics. This was revealed by the finding that bacterial community diversity was positively correlated to lytic viral production in the euphotic zone of the open ocean but was negatively related to lysogenic viral production in the coastal ocean. Such distinct but contrasting correlations suggest that viral life strategies can not only contribute to diversifying bacterial community but also potentially piggyback their host to dominate bacterial community, suggesting the tightly synchronized depth-dependent and habitat-specific diel patterns of virus-host interactions. It further implies that viruses serve as an ecologically important driver of bacterial diel dynamics across the ocean, highlighting the viral roles in bacterial ecological and biogeochemical processes in the ocean.

Influencing factors of knowledge, attitude and behavior in children's palliative care among pediatric healthcare workers: a cross-sectional survey in China.

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: The total score of the PHWs' knowledge, attitude and behavior about CPC was 69.98, which was at a moderate level. PHWs' CPC knowledge, attitude, and behavior are positively correlated.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.

Tests on a scale for measuring the core competencies of paediatric specialist nurses: An exploratory quantitative study.

AIM: This study aimed to develop a tool to measure paediatric specialist nurses' core competencies and examine the scale's validity and reliability. DESIGN: An exploratory quantitative study. METHODS: This study was performed in April 2022 with 302 paediatric specialist nurses in mainland China. Items were created through a literature review, a qualitative interview, and the Delphi method. The data were evaluated using descriptive statistics, independent sample t-test, explanatory factor analysis, Pearson correlation coefficient, Cronbach's alpha coefficient and split-half reliability. RESULTS: The final scale consisted of five factors and 32 items. The factors were communication, coordination and judgement abilities; professional technology mastery ability; specialist knowledge mastery ability; medical-related processes; and evidence-based nursing competencies. The explained total variance of the five factors was 62.216%. The scale-level and item-level CVI of this scale was 1.00, and the mean CVR of the total scale was 0.788. The Pearson correlation coefficients of each dimension and the total dimension of the scale was 0.709-0.892, and within each dimension, it was 0.435-0.651. The Cronbach's α of this scale was 0.944, and its split-half reliability was 0.883.

Repeated introduction of micropollutants enhances microbial succession despite stable degradation patterns.

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.

Unique T4-like phages in high-altitude lakes above 4500 m on the Tibetan Plateau.

Viruses are the most abundant biological entities in the biosphere; however, little is known about viral ecology in high altitude lakes. Here, we characterized viruses from 13 lakes, nine of which located ≥4500 m above sea level, on the Tibetan Plateau, the highest plateau on Earth. The abundance of virus-like particle (VLP) in Tibetan lakes ranged from 4.8 ± 0.2 × 105 VLPs mL-1 to 6.0 ± 0.2 × 107 VLPs mL-1 and the virus-to-bacterium ratio was in the lower range of values reported for other lakes. The viral population size was positively correlated with turbidity and negatively correlated with particulate organic carbon concentration. Highly diverse VLP morphologies, including large (~300 nm) morphotypes, were observed. Phylogenetic analysis of T4-like bacteriophages based on major capsid gene (g23) identified a novel viral group, which were detected in abundance in hyposaline and mesosaline Tibetan lakes. Adaptation to lake evolution, water source (glacier-fed or non-glacier-fed) and environmental conditions (e.g., salinity, phosphorus concentration and productivity) are likely responsible for the variation in T4-like myovirus community composition in contrasting Tibetan lakes. This first investigation of viruses in high-altitude alpine lakes above 4500 m could contribute to our understanding of viral ecology in global alpine lakes.

Viral control of biomass and diversity of bacterioplankton in the deep sea.

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.

Seasonal dynamics of bacterial communities in the surface seawater around subtropical Xiamen Island, China, as determined by 16S rRNA gene profiling.

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.

Estimating Primary Production of Picophytoplankton Using the Carbon-Based Ocean Productivity Model: A Preliminary Study.

Picophytoplankton are acknowledged to contribute significantly to primary production (PP) in the ocean while now the method to measure PP of picophytoplankton (PPPico) 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 PPPico, 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 PPPico whose principle is based on the group-specific abundance, cellular carbon conversion factor (CCF), and temperature-derived growth rate of picophytoplankton. Comparative analysis showed that the estimated PPPico using CbPM method is significantly and positively related (r2 = 0.53, P < 0.001, n = 171) to the measured 14C uptake. This significant relationship suggests that CbPM has the potential to estimate the PPPico over large spatial and temporal scales. Currently this model application may be limited by the use of invariant cellular CCF and the relatively small data sets to validate the model which may introduce some uncertainties and biases. Model performance will be improved by the use of variable conversion factors and the larger data sets representing diverse growth conditions. Finally, we apply the CbPM-based model on the collected data during four cruises in the Bohai Sea in 2005. Model-estimated PPPico ranged from 0.1 to 11.9, 29.9 to 432.8, 5.5 to 214.9, and 2.4 to 65.8 mg C m-2 d-1 during March, June, September, and December, respectively. This study shed light on the estimation of global PPPico using carbon-based production model.

Distributions and relationships of virio- and picoplankton in the epi-, meso- and bathypelagic zones of the Western Pacific Ocean.

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° 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 × 102-6.3 × 104, <34-2.8 × 103, 3.9 × 104-1.3 × 106 cells mL-1 and 5.1 × 105-2.7 × 107 mL-1, respectively), and Prochlorococcus were low (<2.3 × 102-1.0 × 105 cells mL-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. r2 = 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 (r2 = 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.

Comment on "Dilution limits dissolved organic carbon utilization in the deep ocean".

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 marine inducible prophage vB_CibM-P1 isolated from the aerobic anoxygenic phototrophic bacterium Citromicrobium bathyomarinum JL354.

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.

Horizontal and vertical distribution of marine virioplankton: a basin scale investigation based on a global cruise.

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±0.73×10(7) ml(-1) in global surface oceans and decreased from the areas with high chlorophyll concentration (on average, 1.47±0.78×10(7) ml(-1)) to the oligotrophic subtropical gyres (on average, 6.34±2.18×10(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.

Antagonistic roles of abscisic acid and cytokinin during response to nitrogen depletion in oleaginous microalga Nannochloropsis oceanica expand the evolutionary breadth of phytohormone function.

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.

Microbial production of recalcitrant dissolved organic matter: long-term carbon storage in the global ocean.

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.