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  • Blackwell Publishing Ltd  (12)
Publikationsart
Verlag/Herausgeber
Erscheinungszeitraum
  • 1
    Digitale Medien
    Digitale Medien
    A survey on bacteria inhabiting the sea surface microlayer of coastal ecosystems (2005)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 54 (2005), S. 0 
    Details
    ISSN: 1574-6941
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Bacterial populations inhabiting the sea surface microlayer from two contrasted Mediterranean coastal stations (polluted vs. oligotrophic) were examined by culturing and genetic fingerprinting methods and were compared with those of underlying waters (50 cm depth), for a period of two years. More than 30 samples were examined and 487 strains were isolated and screened. Proteobacteria were consistently more abundant in the collection from the pristine environment whereas Gram-positive bacteria (i.e., Actinobacteria and Firmicutes) were more abundant in the polluted site. Cythophaga-Flavobacter–Bacteroides (CFB) ranged from 8% to 16% of total strains. Overall, 22.5% of the strains showed a 16S rRNA gene sequence similarity only at the genus level with previously reported bacterial species and around 10.5% of the strains showed similarities in 16S rRNA sequence below 93% with reported species. The CFB group contained the highest proportion of unknown species, but these also included Alpha- and Gammaproteobacteria. Such low similarity values showed that we were able to culture new marine genera and possibly new families, indicating that the sea-surface layer is a poorly understood microbial environment and may represent a natural source of new microorganisms. Genetic fingerprinting showed, however, no consistent differences between the predominant bacterial assemblages from surface microlayer and underlying waters, suggesting that the presence of a stable and abundant neustonic bacterial community is not a common trait of coastal marine environments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1016/j.femsec.2005.04.002
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  • 2
    Digitale Medien
    Digitale Medien
    Occurrence of Salmonella spp. and Cryptosporidium spp. in a French coastal watershed: relationship with fecal indicators (2003)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 218 (2003), S. 0 
    Details
    ISSN: 1574-6968
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1574-6968.2003.tb11519.x
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  • 3
    Digitale Medien
    Digitale Medien
    Influence of mutation frequency on the persistence of Salmonella enterica serotypes in natural waters (2002)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 41 (2002), S. 0 
    Details
    ISSN: 1574-6941
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1574-6941.2002.tb00973.x
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  • 4
    Digitale Medien
    Digitale Medien
    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
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1574-6941.2001.tb00775.x
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  • 5
    Digitale Medien
    Digitale Medien
    High sequence diversity of Alteromonas macleodii-related cloned and cellular 16S rDNAs from a Mediterranean seawater mesocosm experiment (1999)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 28 (1999), S. 0 
    Details
    ISSN: 1574-6941
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1574-6941.1999.tb00588.x
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  • 6
    Digitale Medien
    Digitale Medien
    Effectiveness of CSE to counterstain particles and dead bacterial cells with permeabilised membranes: application to viability assessment in waters (1999)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 178 (1999), S. 0 
    Details
    ISSN: 1574-6968
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1574-6968.1999.tb08680.x
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  • 7
    Digitale Medien
    Digitale Medien
    Phenotypic and genetic diversity within a colony morphotype (1998)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 160 (1998), S. 0 
    Details
    ISSN: 1574-6968
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1574-6968.1998.tb12903.x
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  • 8
    Digitale Medien
    Digitale Medien
    The accumulation and release of polysaccharides by planktonic cells and the subsequent bacterial response during a controlled experiment (1999)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 29 (1999), S. 0 
    Details
    ISSN: 1574-6941
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1574-6941.1999.tb00626.x
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  • 9
    Digitale Medien
    Digitale Medien
    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
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1574-6941.2001.tb00801.x
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  • 10
    Digitale Medien
    Digitale Medien
    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
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1574-6941.2001.tb00776.x
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