Dynamics of auto- and heterotrophic picoplankton and associated viruses in Lake Geneva

Microbial dynamics have rarely been investigated in Lake Geneva, known as the largest lake in western Europe. From a 5-month survey, we report dynamic patterns of free-living virus, bacteria and small phytoplankton abundances in response to a variety of environmental parameters. For the first time, we fractionated the primary production to separate the contribution of different size-related biological compartments and measured both bacterial and viral production in addition to experiments conducted to quantify the virus-induced bacterial mortality. We observed marked seasonal and vertical variations in picocyanobacteria, bacteria and virus abundances and production. The contribution of picoplankton and nanoplankton production to the total primary production was high (reaching up to 76% of total primary production) in November and the spring–summer transition period, respectively. The impact of viral lysis on both bacteria and picocyanobacteria was significantly higher than grazing activities. Virus-induced picocyanobacterial mortality reached up to 66% of cell removal compared to virus induced (heterotrophic) bacterial mortality, which reached a maximum of 34% in July. Statistical analyzes revealed that temperature and top-down control by viruses are among important factors regulating the picocyanobacterial dynamics in this lake. More generally speaking, our results add to the growing evidence and accepted view nowadays that viruses are an important actor of freshwater microbial dynamics and more globally of the functioning of the microbial food webs

Macrophages Facilitate Resistance to Anti-VEGF Therapy by Altered VEGFR Expression

Abstract Purpose: VEGF-targeted therapies have modest efficacy in cancerpatients, butacquiredresistance iscommon. Themechanisms underlying such resistance are poorly understood. Experimental Design: To evaluate the potential role of immune cells in the development of resistance to VEGF blockade, we first established a preclinical model of adaptive resistance to anti-VEGF therapy. Additional in vitro and in vivo studies were carried out to characterize the role of macrophages in such resistance. Results: Using murine cancer models of adaptive resistance to anti-VEGF antibody (AVA), we found a previously unrecognized roleofmacrophagesinsuchresistance.Macrophageswereactively recruited to the tumor microenvironment and were responsible for the emergence of AVA resistance. Depletion of macrophages following emergence of resistance halted tumor growth and prolonged survival of tumor-bearing mice. In a macrophagedeficient mouse model, resistance to AVA failed to develop, but could be induced by injection of macrophages. Downregulation of macrophage VEGFR-1 and VEGFR-3 expression accompanied upregulation of alternative angiogenic pathways, facilitating escape from anti-VEGF therapy. Conclusions: These findings provide a new understanding of the mechanisms underlying the modest efficacy of current antiangiogenesis therapies and identify new opportunities for combinationapproachesforovarianandothercancers. ClinCancerRes; 23(22); 7034–46. �2017 AACR

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Distinctive Patterns in the Taxonomical Resolution of Bacterioplankton in the Sediment and Pore Waters of Contrasted Freshwater Lakes

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Genome analysis of Marinobacter phage AS1 suggests its close interactions with host Marinobacter sp.

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Seasonal variation in viral-induced mortality of bacterioplankton in the water column of a large mesotrophic lake (Lake Biwa, Japan)

International audienceViruses are ubiquitous and abundant in aquatic systems, yet knowledge of virus-bacteria interactions in thermally stratified water columns of large lakes is limited. We explored the possible factors that affect viral abundance, infection rate, and the relative importance of viral lysis to heterotrophic nanoflagellate (HNF) grazing as a mortality factor of bacterioplankton in the upper (euphotic zone, 5 m) and deeper (aphotic zone, 50 m) layers of the large mesotrophic Lake Biwa,Japan. Data obtained for a full seasonal cycle indicated that bacterial abundance was the best predictor (r2 = 0.85) of viral abundance (range 1.0 × 1010 to 4.1 × 1010 viruses l-1), yielding an average virus:bacteria ratio of 8.2 ± 1.3 (SD). Variation in the frequency of visibly infected cells (range 1.8 to 4.1%) was largely accounted for by the linear combination of bacterial production and HNF abundance (r2 = 0.81, p < 0.001, n = 24). The percentage of daily bacterial production destroyed by viruses was estimated to be high (52.7 ± 16.2%) in the upper layer during the stratification period, which was on average 3.0-fold greater than the percentage of bacterial production consumed by HNF in that layer. In contrast, the corresponding value in the deeper layer was moderate (13.6 ± 5.2%), being 0.6- fold lower than the percentage of bacterial production consumed by HNF. Our data suggest that carbon and nutrient flux patterns controlled by viruses and HNF vary with depth in thermally stratified water columns of Lake Biwa

High and differential viral infection rates within bacterial 'morphopopulations' in a shallow sand pit lake (Lac de Créteil, France).

International audienceThe ecology of viruses in shallow artificial freshwaters is poorly documented and there is no reference for sand pit lakes. We examined the seasonal abundances and infection rates of viruses in the sand pit Lake Créteil (France). Bacteria were the best predictor of viral abundance (4.0-7.8 × 10(10) viruses L(-1) ), with an average virus-to-bacteria ratio of 13.5 ± 1.9. Virus-induced bacterial mortality (range 37-86%, mean 65%) was higher than that in typical pelagic situations. This was related to high specific contact rates between viruses and bacterial hosts and high burst size (BS) estimates. Seasonal fluctuations in viruses and bacteria were rather homeostatic, although temperature was a major driver of microbial activities. Different bacterial morphotypes, i.e. 'morphopopulations', were analysed. Rod cells dominated the total (90%) and infected (89%) communities. Elongated rods were the most infected (45% of infected cells), whereas fat rods exhibited the highest BS estimates (mean=72 viruses per bacterium) due to a larger specific cell volume. We conclude that the lytic activity of viruses is high and heterogeneous for different bacterial-host phenotypes in the sand pit Lake Créteil. A theoretical exercise shows that this can exert a strong influence on the processes occurring in plankton food webs