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  • 1
    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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  • 2
    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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  • 3
    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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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    Autotrophic carbon assimilation and biomass from size-fractionated phytoplankton in the surface waters across the subtropical frontal zone (Indian Ocean) (1999)
    Springer
    Polar biology 21 (1999), S. 90-96 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The composition of the phytoplanktonic communities in the surface waters of the La Reunion-Kerguelen transect (from 38°36S to 46°33S) has been investigated under spring conditions (Antarès 3 cruise, France-JGOFS, 28 September–8 November, 1995). The study, conducted at six stations in the subtropical frontal zone, involved size fractionations (threshold: 2 μm). The large variations in the overall biomass and autotrophic carbon fixation, calculated via Rubisco activity measurements and expressed respectively in terms of μg chlorophyll (a + b + c) per liter and nmol fixed carbon dioxide per liter and per hour, were attributable only to phytoplanktonic cells of 〉2 μm, with a peak observed in the frontal zone. The picophytoplankton (〈2 μm) biomass remained constant throughout the transect, but the evolution of the species composition of the picophytoplanktonic population, as calculated from flow cytometry measurements through this frontal zone, changed. This study provides evidence, for the first time in this area, of the disappearance of prochlorophytes from the south of the frontal zone (42–47°S). Picoeukaryotes (〈2 μm) and cyanobacteria populations, resolved by flow cytometry, were present all along the transect. However, their abundance decreased southward up to the quasi-disappearance of cyanobacteria at the southernmost station (52°S) that is characteristic of antarctic waters. The presence of prochlorophytes that is exclusive to the subtropical surface waters, and the low carbon fixation activity associated with these waters, may be linked to the specific hydrological features encountered. In contrast, the marked reduction in the cyanobacteria and the abundance of picoeukaryotes along the north-south transect is more likely to be a result of the reduction in temperature through the frontal zone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050339
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  • 6
    Electronic Resource
    Electronic Resource
    Smallest eukaryotic organism (1994)
    [s.l.] : Nature Publishing Group
    Nature 370 (1994), S. 255-255 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR - Autotrophic communities of pico-plankton (cell size less than 2 im dia-meter), known to be dominated by prokaryotes1, are essential in the carbon cycle of estuaries2 and oceans1'3. Hall and Vincent report that in other nutrient-rich ecosystems, the eukaryotic forms of the picoplankton "can ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/370255a0
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