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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 218 (2003), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Cryptosporidium and Salmonella are pathogenic microorganisms that can cause severe gastrointestinal illness in humans. Because these organisms are potentially transmitted through natural waters, this study was carried out to estimate the concentrations of both pathogens in a French coastal watershed and to determine the relationships with fecal indicators. Water samples from nine wastewater treatment plants and eight rivers were analyzed. Although both pathogens and indicators are released from sewage effluents, no clear correlation was found between the two enteric pathogens nor between a given pathogen and fecal indicators. These results suggest that fecal indicators do not adequately indicate the presence of Cryptosporidium and Salmonella in natural waters and that pathogens and indicators may have different behaviors in the aquatic environment.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 160 (1998), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Isolates showing different and similar colony morphologies were selected from spread plates of bacteria from seawater samples taken in the northern Adriatic Sea. All isolates were characterised by restriction fragment length polymorphism (RFLP) patterns of their PCR-amplified 16S rRNA gene and by 95 physiological tests (Biolog system). Cluster analysis of both genetic and phenotypic patterns showed that different colony morphotypes were related to different species or biotypes. However, isolates belonging to the more well-defined, conspicuous colony types had a high similarity, whereas those from the less conspicuous colony morphotypes showed high genetic diversity. Although colony morphotypes clearly underestimate taxonomic diversity, they can be used combined with PCR-RFLP analysis and as a preliminary approach for ecological studies aimed at the isolation of different species. Furthermore, for some species forming very conspicuous pigmented colonies, such as some photosynthetic aerobic bacteria, colony morphology may be useful for a rapid and low-cost screening of their distribution in the natural environment, especially when combined with other molecular techniques.
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  • 3
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The CSE dye (Chemunex, Maisons-Alfort, France) was combined with an activity marker to improve bacterial activity assessment in natural waters. Its effectiveness to counterstain dead cells with permeabilised membranes was investigated on live and dead cells of a variety of strains from collections or isolated from the natural environment. Cells were killed by heat treatment. For all strains tested, the fluorescent dye showed an intense staining of killed cells having permeabilised membranes while no significant signal was detected when applied to live cells. Furthermore, the CSE dye had no toxicity on viable cells. Then, CSE was combined with the ChemChrome V6 dye (Chemunex) to assess the activity of bacterial cells in different waters. Both fluorescences were analysed simultaneously by solid-phase cytometry. The active cell counts were sometimes lower when both dyes were combined suggesting that CSE was able to counterstain cells having a residual esterase activity and compromised membranes. These cells were subtracted from the active cell counts determined with ChemChrome V6. In most samples, active cell counts were congruent with those determined by the direct viable count method.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Seawater from the northern Adriatic, with low phosphorus (0.03 μM) and nitrogen (1.0 μM NO3 and 1.0 μM NH4) concentration, was incubated for 12 days in 20-l polycarbonate carboys. The addition of a nutrient mixture (0.6 μM PO4, 5.1 μM NO3, 1.8 μM NH4, 10.6 μM SiO2) induced a strong diatom bloom, reaching 25 μg l−1 Chl a. Primary and bacterial production were stimulated by the initial enrichment of nitrogen and phosphorus but ceased when N and P depletion occurred after 4 days. Inorganic N exhaustion resulted in a significant production (and accumulation) of dissolved and particulate carbohydrates. The initial accumulation of carbohydrates (CHO) in the particulate phase was followed 2 days later by a significant release of dissolved CHO. The bacterial response to this organic carbon source, as reflected by glucosidase activity, was probably inhibited by the severe P limitation following the phytoplankton bloom. In the exponential phase, when P concentration was sufficiently high to sustain a significant glucosidase activity, no increase in either dissolved organic carbon or dissolved total CHO was observed. We hypothesise that the periodic accumulation of dissolved organic carbon in the northern Adriatic is due to an excessive nitrogen enrichment followed by a concurrent N and P limitation.
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  • 5
    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.
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 41 (2002), S. 0 
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In aquatic environments, the survival of pathogenic microorganisms, such as Salmonella spp., may represent a risk to public health. The mutation frequency was hypothesized to influence the persistence of Salmonella serotypes in environmental waters. The mean mutation frequency to rifampin resistance of the 11 major serotypes of Salmonella enterica isolated from the Tech River (Pyrénées-Orientales, France) was determined. Then, a comparison of the survival of three serotypes holding different mutation frequencies showed no significant differences, suggesting that a high mutation rate was not directly linked to increased persistence of Salmonella cells under stressful conditions. However, we demonstrated, via controlled experiments, that long-term starvation in natural water could influence the mutation frequency of the Salmonella Typhimurium serotype. This effect, which was not observed for the serotypes Virchow and Infantis, could be a way of adapting to stressful conditions for the serotype Typhimurium and could explain its recurrence in aquatic systems.
    Type of Medium: Electronic Resource
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  • 7
    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.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 29 (1999), S. 0 
    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.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 22 (1997), S. 0 
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The succession of the physiological states of Salmonella typhimurium cells under starvation-survival conditions in artificial seawater was investigated by flow cytometry and epifluorescence microscopy using direct examination of different cell functions. Measurements of substrate responsiveness (DVC method), real and potential respiration (redox dye 5-cyano-2,3-ditolyl tetrazolium chloride, CTC), membrane permeability (BacLight™ kit), as well as DNA content (Hoechst 33342 staining) reveal an important heterogeneity within the population, and suggest a progressive physiological cell alteration throughout the starvation process. The transition steps between culturable and prelytic cells are described.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Small subunit rDNA clone libraries were generated from amplified DNA of bacterioplankton taken at different time points from a mesocosm containing eutrophied Mediterranean seawater and made eutrophic by the addition of N and P. Analysis of 96 partial sequences indicated that 22% of the clones formed four clusters which showed the highest sequence similarity with the 16S rDNA sequence of Alteromonas macleodii DSM 6062T. A fifth cluster, comprising 31% of the clone sequences is moderately related to the A. macleodii sequence. Similarity between the almost complete sequences of two representatives of clone clusters 1, 2 and 3 and A. macleodii ranged between 97.7 and 98.1%. Four oligonucleotide probes, representing four clone clusters, were developed on the basis of partial clone sequences. Dot blot hybridization with PCR-amplified 16S rDNA from 739 clones revealed that 24% of clones belong to one of these clusters. Dot blot hybridization between the four probes and PCR-amplified 16S rDNA from 128 strains isolated from the mesocosm identified 21% of the isolates possessing the probe target region. While probes GP-1 and GP-4 unambiguously identified 0.8 and 4.0% of the strains, respectively, probes GP-2 and GP-3 showed cross hybridization with 16% of the strains. Analysis of the probe target region of the 16S rDNA of one of the isolates indeed demonstrated the presence of double peaks in the relevant region of the sequence which is indicative of microheterogeneity at the rrn operon level. Although some of the diversity can be attributed to intra-strain variation, the data indicate that the phylogenetic diversity of A. macleodii is higher than represented by the type strain of this species.
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