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  • 1
    Electronic Resource
    Electronic Resource
    Contribution of heterotrophic bacterial production to the carbon budget of the river Seine (France) (1993)
    Springer
    Microbial ecology 25 (1993), S. 19-33 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Bacterial activity was measured in the river Seine by two methods, 3H-thymidine incorporation into DNA and 3H-leucine incorporation into proteins. Both incorporation rates are characterized by low values upstream of Paris, a large increase just downstream of the outfall of the Achères treatment plant effluents, and then decreasing values further downstream. The covariation of both activities is demonstrated by the constancy of the molar ratio (leucine to thymidine incorporation rate) in the range of 6 to 8 for all the samples, except in the perturbed area where it is higher (15 to 35). These high values of molar ratio are linked to the introduction into the river of large sized bacteria (⩾1 µm) with higher incorporation rates per cell or biomass unit than the small autochthonous bacteria (〈 1 µm). Growth rates of large bacteria were on average 3.7 times higher than those of small bacteria. Bacterial production was calculated with experimentally determined conversion factors (0.5 × 1018 cells per mole of thymidine incorporated and 900 gC per mole of leucine incorporated) and by taking into account the activity of both size classes of bacteria measured through fractionation experiments (post-incubation filtration). Production estimated in the perturbed area downstream of Ach6res was very high, up to 60 µgC liter−1h−1 in the summer. Carbon consumption by bacteria in the area perturbed by the Ach6res effluents was calculated assuming a growth yield of 0.2 and compared to the load of biodegradable organic matter discharged by the treatment plant. In summer, an additional supply of organic matter is required to account for the intense bacterial activity, suggesting the importance of phytoplankton production in the carbon budget.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00182127
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  • 2
    Electronic Resource
    Electronic Resource
    Abundance and biomass of heterotrophic microorganisms in Lake Tanganyika (2005)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 50 (2005), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. This study focused on heterotrophic microorganisms in the two main basins (north and south) of Lake Tanganyika during dry and wet seasons in 2002. Bacteria (81% cocci) were abundant (2.28–5.30 × 106 cells mL−1). During the dry season, in the south basin, bacterial biomass reached a maximum of 2.27 g C m−2 and phytoplankton biomass was 3.75 g C m−2 (integrated over a water column of 100 m).2. Protozoan abundance was constituted of 99% of heterotrophic nanoflagellates (HNF). Communities of flagellates and bacteria consisted of very small but numerous cells. Flagellates were often the main planktonic compartment, with a biomass of 3.42–4.43 g C m−2. Flagellate biomass was in the same range and often higher than the total autotrophic biomass (1.60–4.72 g C m−2).3. Total autotrophic carbon was partly sustained by the endosymbiotic zoochlorellae Strombidium. These ciliates were present only in the euphotic zone and usually contributed most of the biomass of ciliates.4. Total heterotrophic ciliate biomass ranged between 0.35 and 0.44 g C m−2. In 2002, heterotrophic microorganisms consisting of bacteria, flagellates and ciliates represented a large fraction of plankton. These results support the hypothesis that the microbial food web contributes to the high productivity of Lake Tanganyika.5. As the sole source of carbon in the pelagic zone of this large lake is phytoplankton production, planktonic heterotrophs ultimately depend on autochthonous organic carbon, most probably dissolved organic carbon (DOC) from algal excretion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.2005.01395.x
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  • 3
    Electronic Resource
    Electronic Resource
    Bacterial production measured by leucine and thymidine incorporation rates in French lakes (1999)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 42 (1999), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Production of heterotrophic bacterioplankton was estimated monthly by the tritiated thymidine and leucine incorporation methods during the draining and filling of the mesotrophic Lake Pareloup (over a 2.5-years sampling program).2. Rates of 3H-leucine (leu) and 3H-thymidine (thy DNA) incorporation generally paralleled each other but the ratio of leu/thy DNA incorporation rates was higher for the draining period (34.5 mean) than during and after filling (11.5 mean).3. After draining, the highest ratios were observed during periods of low temperature and low bacterial specific activity, while DNA labeling by 3H-thymidine was reduced. However, bacterial production estimates obtained by 3H-leucine (BPL) and 3H-thymidine (BPT) incorporation methods were generally well correlated and the average BPL/BPT ratio was equal to 0.78.4. In addition, both methods were applied during a diel cycle in three lakes of different trophic status. An increase of leu/thy DNA incorporation rates was noted from the oligotrophic to the eutrophic system. In the absence of Cyanobacteria, BPL and BPT values were quite concordant on average.5. In situations of unbalanced growth, BPL and BPT values can diverge but when considered over a sufficient period of time they were found to be in agreement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.1999.00500.x
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  • 4
    Electronic Resource
    Electronic Resource
    Flow cytometric discrimination of bacterial populations in seawater based on SYTO 13 staining of nucleic acids (1999)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 29 (1999), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Flow cytometric (FCM) counts of bacteria stained with SYTO 13, a cyanine dye, were highly correlated with DAPI epifluorescence microscopic counts in coastal seawater samples. Fluorescence intensity of stained cells appeared to depend on nucleic acid content and on the polarization of cell membranes. Right angle light scatter values of bacterial populations were clearly related to cell size. By FCM analysis of SYTO 13-stained samples from a batch mesocosm of Mediterranean seawater, several bacterial clusters having different apparent sizes and physiological status were discriminated showing that FCM analysis allows key cell categories to be followed for understanding bacterial community dynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1999.tb00623.x
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  • 5
    Electronic Resource
    Electronic Resource
    Are the actively respiring cells (CTC+) those responsible for bacterial production in aquatic environments? (2001)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 35 (2001), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) staining method is commonly and increasingly used to detect and to enumerate actively respiring cells (CTC+ cells) in aquatic systems. However, this method remains controversial since some authors promote this technique while others pointed out several drawbacks of the method. Using flow cytometry (FCM), we showed that CTC staining kinetics vary greatly from one sample to another. Therefore, there is no universal staining protocol that can be applied to aquatic bacterial communities. Furthermore, using 3H-leucine incorporation, it was shown that the CTC dye has a rapid toxic effect on bacterial cells by inhibiting protein synthesis, a key physiological function. The coupling of radioactive labelling with cell sorting by FCM suggested that CTC+ cells contribute to less than 60% of the whole bacterial activity determined at the community level. From these results, it is clearly demonstrated that the CTC method is not valid to detect active bacteria, i.e. cells responsible for bacterial production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.2001.tb00801.x
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  • 6
    Electronic Resource
    Electronic Resource
    Microbial community dynamics in Mediterranean nutrient-enriched seawater mesocosms: changes in the genetic diversity of bacterial populations (2001)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 34 (2001), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A mesocosm experiment was performed to study the influence of nutrients on activity and diversity of bacterial assemblages from the Mediterranean Sea. Changes in the diversity of the predominant bacterial populations were monitored by DGGE fingerprinting of PCR products derived from 16S rRNA encoding genes. Fluctuations in the diversity of the most active populations was inferred by performing the DGGE fingerprinting on the basis of the cellular rRNA after reverse transcription and PCR amplification. DNA-derived DGGE patterns obtained from duplicate control and nutrient-enriched mesocosms showed differences in the development of the bacterial communities between control and nutrient-enriched experimental mesocosms. Multidimensional scaling analysis of the DNA-derived DGGE fingerprints indicated that duplicate treatments were reproducible. DNA- and RNA-derived DGGE fingerprints of bacterial assemblages changed over time, showing that the composition of the bacterial assemblages, as well as the most active bacterial populations changed during different phases of the incubation. Sequences of predominant DGGE bands in RNA-derived patterns were similar to 16S rRNA gene sequences of members of the α-, γ- and δ-Proteobacteria and of the Cytophaga-Flavobacterium-Bacteroides phylum (CFB). Bands corresponding to Ruegeria-like bacteria and members of the CFB became especially dominant during the course of incubation, suggesting that these populations were important contributors to bacterial production and activity in the post-grazing phase of the experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.2001.tb00775.x
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  • 7
    Electronic Resource
    Electronic Resource
    Microbial community dynamics in Mediterranean nutrient-enriched seawater mesocosms: changes in abundances, activity and composition (2001)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 34 (2001), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Quantitative and qualitative changes in bacterial communities from the Mediterranean Sea were compared in duplicate batch mesocosms with or without addition of inorganic nutrients. Methods including traditional microbial ecology techniques, molecular biology and flow cytometry were combined to determine abundances, production, cell size, activity, culturability and taxonomic diversity of bacterial cells. Addition of nutrients and confinement resulted in an increase of bacterial densities which were rapidly controlled by protozoan grazing. Changes in bacterial activity and morphology were observed during the growth phase of bacteria and under grazing pressure. The proportion of medium-size and culturable cells increased during the growth phase. These cells were preferentially consumed by grazers resulting in a strong limitation of bacterial production. As a consequence of the grazing pressure, large cells were produced and contributed to the remaining bacterial productivity after grazing. Grazing had an effect on the taxonomic composition of bacterial communities by preferentially eliminating γ-Proteobacteria, α-Proteobacteria were preserved. It seems that some species from the genera Ruegeria and Cytophaga may have developed defence strategies to escape predation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.2001.tb00776.x
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  • 8
    Electronic Resource
    Electronic Resource
    Dynamics of bacterioplankton in oligotrophic and eutrophic aquatic environments: bottom-up or top-down control? (1990)
    Springer
    Hydrobiologia 207 (1990), S. 37-42 
    Details
    ISSN: 1573-5117
    Keywords: Bacterioplankton ; bacterial growth rate ; bacterial mortality ; bacterial grazing ; oligotrophy ; eutrophy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Measurements of bacterial biomass, production and mortality have been carried out in a large range of aquatic environments, including eutrophic and oligotrophic ones. The general trends of variations of bacterial biomass, size, specific growth rate and mortality rate in all these environments are examined. The overall flux of bacterial production is taken as an index of the flux of organic matter available to bacteria, thus characterizing the richness of the environment. Bacterial biomass is roughly proportional to richness, while mean cell size increases with it. The turnover rate of biomass, as revealed either by growth or by mortality rates, appears to be fairly independent of richness. These observations are compatible with a simple resource-limited (bottom-up controlled) model of the dynamics of bacterioplankton. On the other hand, they are in contradiction with the predictions of a predator-controlled (top-down controlled) model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00041438
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  • 9
    Electronic Resource
    Electronic Resource
    River ecosystem modelling: application of the PROSE model to the Seine river (France) (1998)
    Springer
    Hydrobiologia 373-374 (1998), S. 27-45 
    Details
    ISSN: 1573-5117
    Keywords: Seine river ; ecological modelling ; validation ; anthropic impacts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Seine river crosses the most densely populated and industrialized area of France, Paris (16 million inhabitants), surrounded by fertile land with intensive agriculture. In the framework of a CNRS (Scientific Research National Center) research project, computer programs have been designed to tackle problems related to eutrophication, non-point pollution and the impact of sewage during dry or wet periods (urban runof and sewage network overflow). The PROSE software has been specially designed to simulate the behaviour of the most disturbed stretches of the Seine ecosystem on the last 300 kilometers of the river, upstream of the estuarine area. The 1-D hydraulic sub-model of PROSE is based on a finite difference solution of Saint-Venant equations solved with the Preissman scheme. It simulates steady state situations as well as highly transient situations such as fast changes in river discharge during rainy periods or dam motions. The biological sub-model is based on the RIVE model, describing the major processes in a river ecosystem: primary production, heterotrophic bacterial activity and organic matter decomposition, major nutrients species (nitrogen, phosphorus), nitrifying activity and oxygen balance. Water column and sediment variables are simulated. Most of the parameters have been estimated during laboratory experiments or field studies. Different situations observed between 1989 and 1991 allowed a detailed validation of the model. The model was then used to explore the reaction of the ecosystem (particularly its oxygen status) to changes in physical constrains (discharge, reoxygenation at dams) or in biological processes (release of microorganisms accompanying waste water discharge).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017045522336
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  • 10
    Electronic Resource
    Electronic Resource
    Bacterioplanktonic biomass and production in the river Meuse (Belgium) (1989)
    Springer
    Hydrobiologia 174 (1989), S. 99-110 
    Details
    ISSN: 1573-5117
    Keywords: river Meuse ; bacterial biomass ; thymidine incorporation ; bacterial production ; growth yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This paper presents results of bacterial biomass determination by epifluorescence microscopy after acridine orange staining and 3H-thymidine incorporation measurements in the river Meuse. Bacterial production is calculated from thymidine incorporation using an experimental conversion factor (0.5 1018 bacterial cells produced per mole of thymidine incorporated into macromolecules). Seasonal variations of bacterial biomass and production at two stations are presented. Biomass ranges between 0.05 mgC · 1−1 (in winter) and 0.8 mgC · 1−1 (in summer). The variations of bacterial production seem to be closely linked to those of primary production; values lower than 1 µgC · 1−1 · h−1 are found in winter and high values (〉 5 µgC 1−1 · h −1) in summer. Longitudinal profiles in the Belgian course of the river show important increase of biomass and production from upstream to downstream. Bacterial growth yield (Y) has been determined (Y = 0.3) in order to calculate bacterial carbon uptake from bacterial production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00014058
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