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

2013 ◽  
Vol 10 (7) ◽  
pp. 8715-8746 ◽  
Author(s):  
A. Parvathi ◽  
X. Zhong ◽  
A. S. Pradeep Ram ◽  
S. Jacquet
Keyword(s):  
Primary Production ◽  
Western Europe ◽  
Transition Period ◽  
Critical Role ◽  
Environmental Parameters ◽  
Lake Geneva ◽  
Microbial Dynamics ◽  
Viral Lysis ◽  
Bacterial Mortality ◽  
The Impact

Abstract. Microbial dynamics has been rarely investigated in Lake Geneva, which is paradoxically the largest lake in Western Europe. From a 5 month survey, we report dynamic patterns of free living viruses, 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 appreciate 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 in November and 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% compared to virus induced bacterial mortality that reached a maximum of 34% in July. Statistical analyses revealed a complex interplay between biological abundances and/or activity with environmental factors in Lake Geneva. Our results provide new evidence on the critical role played by viruses in freshwater microbial dynamics and more globally on the functioning of the microbial food webs. This study highlights the importance of further considering this biological compartment for a better understanding of the plankton ecology of Lake Geneva, especially for modeling purposes and in a context of reoligotrophication and warming of this ecosystem.

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

2014 ◽  
Vol 18 (3) ◽  
pp. 1073-1087 ◽  
Author(s):  
A. Parvathi ◽  
X. Zhong ◽  
A. S. Pradeep Ram ◽  
S. Jacquet
Keyword(s):  
Primary Production ◽  
Western Europe ◽  
Transition Period ◽  
Environmental Parameters ◽  
Lake Geneva ◽  
Microbial Dynamics ◽  
Viral Lysis ◽  
Bacterial Mortality ◽  
Total Primary Production ◽  
The Impact

Abstract. 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.

scholarly journals Assessing the microbial community dynamics and the role of bacteriophages in bacterial mortality in Lake Geneva

2006 ◽  
Vol 19 (2) ◽  
pp. 115-126 ◽  
Author(s):  
Solange Duhamel ◽  
Isabelle Domaizon-Pialat ◽  
Sébastien Personnic ◽  
Stéphan Jacquet
Keyword(s):  
Community Dynamics ◽  
Heterotrophic Bacteria ◽  
Critical Role ◽  
Lake Geneva ◽  
Bacterial Mortality ◽  
Microbial Community Dynamics ◽  
First Time ◽  
New Evidence

SummaryThe aims of this work were to study, for the first time, the succession of microbial communities (from viruses to ciliates) in the largest occidental European lake (Lake Geneva) and to perform two one-weekin situexperiments in March-April (Exp1) and May (Exp2) 2004 in order to assess both small flagellate protozoan and virus-induced mortality of heterotrophic bacteria. Both nanoflagellates and viruses could be responsible for 31 to 42% of the total daily mortality of heterotrophic bacteria. In May (Exp2), viruses could explain up to 10% of the bacterial mortality whereas flagellates were responsible for 32% of the bacterioplankton removal. These results provide new evidence for the critical role played by viruses in the functioning of the microbial food webs and highlight the importance of further considering this biological compartment for a better understanding of the plankton ecology of Lake Geneva.

scholarly journals Seasonal variations of viral- and nanoflagellate-mediated mortality of heterotrophic bacteria in the coastal ecosystem of subtropical Western Pacific

2012 ◽  
Vol 9 (12) ◽  
pp. 17235-17261 ◽  
Author(s):  
A.-Y. Tsai ◽  
G.-C. Gong ◽  
J. Hung
Keyword(s):  
Growth Rates ◽  
Seasonal Variations ◽  
Heterotrophic Bacteria ◽  
Bacterial Biomass ◽  
Dilution Method ◽  
Mortality Factors ◽  
Viral Lysis ◽  
Bacterial Mortality ◽  
Aquatic Food ◽  
The Impact

Abstract. Since viral lysis and nanoflagellate grazing differ in their impact on the aquatic food web, it is important to assess the relative importance of both bacterial mortality factors. In this study, an adapted version of the modified dilution method was applied to simultaneously estimate the impact of both viral and nanoflagellate grazing on the mortality of heterotrophic bacteria. A series of experiments was conducted monthly from April to December 2011 and April to October 2012. The growth rates of bacteria we measured ranged from 0.078 h−1 (April 2011) to 0.42 h−1 (September 2011), indicating that temperature can be important in controlling the seasonal variations of bacterial growth. Furthermore, it appeared that seasonal changes in nanoflagellate grazing and viral lysis could account for 34% to 68% and 13% to 138% of the daily removal of bacterial production, respectively. We suggest that nanoflagellates grazing might play a key role in controlling bacterial biomass and might exceed the impact of viral lysis during the summer period (July to August), because of the higher abundance of nanoflagellates at that time. Viral lysis, on the other hand, was identified as the main cause of bacterial mortality between September and December. Based on these findings in this study, the seasonal variations in bacterial abundance we observed can be explained by a scenario in which both growth rates and loss rates (grazing + viral lysis) influence the dynamics of the bacteria community.

scholarly journals Seasonal variations of virus- and nanoflagellate-mediated mortality of heterotrophic bacteria in the coastal ecosystem of subtropical western Pacific

2013 ◽  
Vol 10 (5) ◽  
pp. 3055-3065 ◽  
Author(s):  
A. Y. Tsai ◽  
G.-C. Gong ◽  
J. Hung
Keyword(s):  
Growth Rates ◽  
Seasonal Variations ◽  
Heterotrophic Bacteria ◽  
Bacterial Biomass ◽  
Dilution Method ◽  
Mortality Factors ◽  
Viral Lysis ◽  
Bacterial Mortality ◽  
Aquatic Food ◽  
The Impact

Abstract. Since viral lysis and nanoflagellate grazing differ in their impact on the aquatic food web, it is important to assess the relative importance of both bacterial mortality factors. In this study, an adapted version of the modified dilution method was applied to simultaneously estimate the impact of both virus and nanoflagellate grazing on the mortality of heterotrophic bacteria. A series of experiments was conducted monthly from April to December 2011 and April to October 2012. The growth rates of bacteria we measured ranged from 0.078 h−1 (April 2011) to 0.42 h−1 (September 2011), indicating that temperature can be important in controlling the seasonal variations of bacterial growth. Furthermore, it appeared that seasonal changes in nanoflagellate grazing and viral lysis could account for 34% to 68% and 13% to 138% of the daily removal of bacterial production, respectively. We suggest that nanoflagellate grazing might play a key role in controlling bacterial biomass and might exceed the impact of viral lysis during the summer period (July to August) because of the higher abundance of nanoflagellates at that time. Viral lysis, on the other hand, was identified as the main cause of bacterial mortality between September and December. Based on these findings in this study, the seasonal variations in bacterial abundance we observed can be explained by a scenario in which both growth rates and loss rates (grazing + viral lysis) influence the dynamics of the bacteria community.

High-resolution spatiotemporal heterogeneities of water optical properties in a large lake to infer physical and biogeochemical drivers of primary production

2020 ◽  
Author(s):  
Camille Minaudo ◽  
Daniel Odermatt ◽  
Bieito Fernandez-Castro ◽  
Hannah E. Chmiel ◽  
Sébastien Lavanchy ◽  
...  
Keyword(s):  
Optical Properties ◽  
Primary Production ◽  
Transition Period ◽  
Alternative Methods ◽  
Lake Geneva ◽  
Short Term ◽  
Large Lakes ◽  
Vertical Heterogeneity ◽  
Basin Scale ◽  
Over The Top

<p>Measuring primary production (PP) is of major importance to evaluate how lakes are recovering from eutrophication, and better constrain their role in global biogeochemical cycles. The classical sampling method involving radiolabelled carbon incubated in bottles at selected depths is associated with heavy logistics and prevents scientists from sampling the short-term dynamics of PP. Therefore, we investigate alternative methods based on oxygen sensors and optical properties.</p><p>To explore the interplay between biogeochemical and physical processes and how they are related to PP in large lakes, we have deployed since October 2018 a sophisticated autonomous profiler in Lake Geneva, Switzerland. The so-called Thetis profiler measures with a centimeter resolution backscattering and fluorescence at discrete wavelengths, hyperspectral absorption and attenuation, hyperspectral reflectance, along with temperature, dissolved oxygen and conductivity. The profiler was deployed over contrasted seasons and recorded these parameters every three hours over the top 50 m of the water column.</p><p>Observations revealed large spatiotemporal heterogeneities of optical properties as a result of seasonal and short-term (weekly to sub-daily) physical and biogeochemical processes. Diel cycles in the optical properties representing phytoplankton abundance resulted from night-time convection and grazing and production during the day. Short-lived but strong upwelling events triggered sudden disruptive shifts in the phytoplankton community composition over the fall to winter transition period which, in turn, impacted the oxygen budgets, opening the door to a better understanding of the vertical heterogeneity of PP directly from inherent optical properties. The data also features advected riverine and resuspended sediments during storms and snowmelt, and during upwelling events, respectively.</p><p>This in-situ data is now being combined with remotely sensed water quality parameters (OLCI products from Sentinel 3A and 3B) and a three-dimensional hydrodynamic model of Lake Geneva (www.meteolakes.ch) to upscale PP estimates from local to basin scale.</p>

The Laryngeal Epithelium in Reflux

2011 ◽  
Vol 21 (3) ◽  
pp. 112-117 ◽  
Author(s):  
Elizabeth Erickson-Levendoski ◽  
Mahalakshmi Sivasankar
Keyword(s):  
Laryngopharyngeal Reflux ◽  
Critical Role ◽  
Structure And Function ◽  
Laryngeal Disease ◽  
Health And Disease ◽  
And Function ◽  
The Impact

The epithelium plays a critical role in the maintenance of laryngeal health. This is evident in that laryngeal disease may result when the integrity of the epithelium is compromised by insults such as laryngopharyngeal reflux. In this article, we will review the structure and function of the laryngeal epithelium and summarize the impact of laryngopharyngeal reflux on the epithelium. Research investigating the ramifications of reflux on the epithelium has improved our understanding of laryngeal disease associated with laryngopharyngeal reflux. It further highlights the need for continued research on the laryngeal epithelium in health and disease.

Anne O. Krueger, Constantine Michalopoulos and Vernon W. Ruttan. Aid and Development. Baltimore: The Johns Hopkins University Press. 1989. xiv + 386 pp.Price: U.S. $ 52.00

1991 ◽  
Vol 30 (2) ◽  
pp. 213-217
Author(s):  
Mir Annice Mahmood
Keyword(s):  
United States ◽  
Economic Development ◽  
International Development ◽  
Western Europe ◽  
Development Assistance ◽  
The United States ◽  
Social Infrastructure ◽  
Low Literacy ◽  
The Subject ◽  
The Impact

Foreign aid has been the subject of much examination and research ever since it entered the economic armamentarium approximately 45 years ago. This was the time when the Second World War had successfully ended for the Allies in the defeat of Germany and Japan. However, a new enemy, the Soviet Union, had materialized at the end of the conflict. To counter the threat from the East, the United States undertook the implementation of the Marshal Plan, which was extremely successful in rebuilding and revitalizing a shattered Western Europe. Aid had made its impact. The book under review is by three well-known economists and is the outcome of a study sponsored by the Department of State and the United States Agency for International Development. The major objective of this study was to evaluate the impact of assistance, i.e., aid, on economic development. This evaluation however, was to be based on the existing literature on the subject. The book has five major parts: Part One deals with development thought and development assistance; Part Two looks at the relationship between donors and recipients; Part Three evaluates the use of aid by sector; Part Four presents country case-studies; and Part Five synthesizes the lessons from development assistance. Part One of the book is very informative in that it summarises very concisely the theoretical underpinnings of the aid process. In the beginning, aid was thought to be the answer to underdevelopment which could be achieved by a transfer of capital from the rich to the poor. This approach, however, did not succeed as it was simplistic. Capital transfers were not sufficient in themselves to bring about development, as research in this area came to reveal. The development process is a complicated one, with inputs from all sectors of the economy. Thus, it came to be recognized that factors such as low literacy rates, poor health facilities, and lack of social infrastructure are also responsible for economic backwardness. Part One of the book, therefore, sums up appropriately the various trends in development thought. This is important because the book deals primarily with the issue of the effectiveness of aid as a catalyst to further economic development.

scholarly journals The lung–gut axis during viral respiratory infections: the impact of gut dysbiosis on secondary disease outcomes

2021 ◽  
Author(s):  
Valentin Sencio ◽  
Marina Gomes Machado ◽  
François Trottein
Keyword(s):  
Gut Microbiota ◽  
Bacterial Infections ◽  
Respiratory Infections ◽  
Critical Role ◽  
Good Health ◽  
Disease Outcomes ◽  
And Function ◽  
Viral Respiratory Infections ◽  
The Impact ◽  
Viral Respiratory

AbstractBacteria that colonize the human gastrointestinal tract are essential for good health. The gut microbiota has a critical role in pulmonary immunity and host’s defense against viral respiratory infections. The gut microbiota’s composition and function can be profoundly affected in many disease settings, including acute infections, and these changes can aggravate the severity of the disease. Here, we discuss mechanisms by which the gut microbiota arms the lung to control viral respiratory infections. We summarize the impact of viral respiratory infections on the gut microbiota and discuss the potential mechanisms leading to alterations of gut microbiota’s composition and functions. We also discuss the effects of gut microbial imbalance on disease outcomes, including gastrointestinal disorders and secondary bacterial infections. Lastly, we discuss the potential role of the lung–gut axis in coronavirus disease 2019.

scholarly journals Impact of alternative regional trade arrangements on the Ethiopian economy

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Habtamu Shiferaw Amogne ◽  
Taiji Hagiwara
Keyword(s):  
Transition Period ◽  
Terms Of Trade ◽  
Endowment Effect ◽  
Welfare Loss ◽  
Customs Union ◽  
Regional Trade ◽  
Partnership Agreement ◽  
Saving Effect ◽  
The Impact ◽  
Trade And Investment

AbstractThe Common Market for Eastern and Southern Africa (COMESA) is a Free Trade Area (FTA) regional trade agreement in Africa. Currently, Ethiopia is negotiating to join COMESA FTA. This study assesses the impact of three regional trade arrangements, COMESA FTA, customs unions, and the European Partnership Agreement (EPA) on the economy of Ethiopia. The analysis is based on a static Global Trade Analysis Project (GTAP) model, version 9 database. Unlike previous studies, the customs union scenarios are designed at the detailed Harmonized System (HS) level. COMESA FTA (scenario 1) with standard GTAP model results in a welfare loss for Ethiopia due to negative terms of trade and investment-saving effect, but with unemployment closure (scenario 2); Ethiopia enjoys a welfare gain mainly due to endowment effect. In scenario 3 (COMESA customs union) and scenario 4 (European Partnership Agreement), Ethiopia loses due to negative terms of trade and investment-saving effect. There is a large increase in demand for unskilled labor force in Ethiopia by around US$23 million, US$112 million, and US$43 million for scenario 2, 3, and 4 respectively. Moreover, there is a positive output effect for oilseeds, leather, and basic metals across all scenarios. The world, as a whole, enjoys welfare gains with COMESA FTA (scenario 1 and 2). However, with scenario 3 and 4, there is an overall welfare loss. There is no strong reason for Ethiopia to move to the customs union, and the EPA in the short run. Therefore, a transition period is necessary, but it is recommended for Ethiopia to join COMESA FTA.

scholarly journals Methionine Diet Evoked Hyperhomocysteinemia Causes Hippocampal Alterations, Metabolomics Plasma Changes and Behavioral Pattern in Wild Type Rats

2021 ◽  
Vol 22 (9) ◽  
pp. 4961
Author(s):  
Maria Kovalska ◽  
Eva Baranovicova ◽  
Dagmar Kalenska ◽  
Anna Tomascova ◽  
Marian Adamkov ◽  
...  
Keyword(s):  
Morphological Changes ◽  
Brain Area ◽  
Critical Role ◽  
Cerebrovascular Diseases ◽  
Behavioral Pattern ◽  
Cell Physiology ◽  
Male Wistar Rats ◽  
High Level ◽  
Hippocampal Alterations ◽  
The Impact

L-methionine, an essential amino acid, plays a critical role in cell physiology. High intake and/or dysregulation in methionine (Met) metabolism results in accumulation of its intermediate(s) or breakdown products in plasma, including homocysteine (Hcy). High level of Hcy in plasma, hyperhomocysteinemia (hHcy), is considered to be an independent risk factor for cerebrovascular diseases, stroke and dementias. To evoke a mild hHcy in adult male Wistar rats we used an enriched Met diet at a dose of 2 g/kg of animal weight/day in duration of 4 weeks. The study contributes to the exploration of the impact of Met enriched diet inducing mild hHcy on nervous tissue by detecting the histo-morphological, metabolomic and behavioural alterations. We found an altered plasma metabolomic profile, modified spatial and learning memory acquisition as well as remarkable histo-morphological changes such as a decrease in neurons’ vitality, alterations in the morphology of neurons in the selective vulnerable hippocampal CA 1 area of animals treated with Met enriched diet. Results of these approaches suggest that the mild hHcy alters plasma metabolome and behavioural and histo-morphological patterns in rats, likely due to the potential Met induced changes in “methylation index” of hippocampal brain area, which eventually aggravates the noxious effect of high methionine intake.

Sign in / Sign up

Export Citation Format

Share Document