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  • 1
    Electronic Resource
    Electronic Resource
    Extracellular enzymatic activity and secondary production in free-living and marine-snow-associated bacteria (1992)
    Springer
    Marine biology 113 (1992), S. 341-347 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Abundance, production (measured as thymidine incorporation) and extracellular enzymatic activity in free-living and marine-snow-associated bacteria were measured in the northern Adriatic Sea. Although bacterial density and production were similar in both free-living and marine-snow-associated bacteria, hydrolytic activity (α- and β-glucosidase and l-aminopeptidase) was significantly higher in marine-snow-associated bacteria, in terms of both absolute and per-cell rates. As concentrations of dissolved total and monomeric carbohydrates and free amino acids in marine snow were very close to those in the ambient water, we suggest that the observed differences between free-living and marine-snow-associated baycteria do not simply reflect catabolic repression of enzyme expression in one of the bacterial components. Whether substrate induction is responsible for the observed higher hydrolase activity in marine-snow bacteria and/or whether there are distinct bacterial species obligatorily associated with marine snow remains unknown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00347289
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  • 2
    Electronic Resource
    Electronic Resource
    Bacterial activity along a trophic gradient (1992)
    Springer
    Microbial ecology 24 (1992), S. 243-257 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Bacterial biomass, secondary production, and extracellular enzymatic activity [α-glucosidase and leucine-aminopeptidase, measured as cleavage of artificial fluorogenic substrates 4-methyl umbelliferyl (MVF) α-D-glucopyranoside and L-leucine 7-amido-4-methyl coumarin (MCA)] were measured along a trophic gradient in the Northern Adriatic Sea in four ecologically different situations. Bacterial parameters were compared with chlorophyll a and inorganic and organic nutrient concentrations. Bacterial secondary production and extracellular enzymatic activity markedly changed among different seasons and along the trophic gradient. Average bacterial secondary production increased from 0.61 to 2.09 µg Cl−1 hour−1 preceding a bloom, to 2.09 µg Cl−1 hour−1 during the bloom, decreasing again to 0.81 and 0.83 µg Cl−1 hour−1 in the post-bloom and summer periods, respectively (values from 0.5 m depth). Leucine-aminopeptidase activity showed more consistent trends than α-glucosidase activity. Average values of leucine-aminopeptidase activity, measured by enzymatic release of MCA, increased from a pre-bloom value of 164.0 to 1,712.0 (nM MCA) hour−1 released during a bloom, decreasing to 298.5 and 133.7 (nM MCA) hour−1 released for the post-bloom and summer situation, respectively (values from 0.5 m depth). Average growth rates decreased during the bloom, whereas average extracellular enzymatic activity levels expressed on a cell basis increased by an average factor of 2. Along the trophic gradient, a consistent increase in bacterial secondary production could be observed in all but the summer situation (values from 0.5 m depth). Leucine-aminopeptidase activity also showed positive trends along the gradient, while α-glucosidase activity did not exhibit such a clear trend. Bacterial biomass trends were less obvious considering both seasonal changes and the tropic gradient. Highly significant interrelations were detected between bacterial proteolytic activity, secondary production, chlorophyll a content, and nitrate concentrations, especially in the surface horizon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00167784
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  • 3
    Electronic Resource
    Electronic Resource
    Dynamics in bacterial surface properties of a natural bacterial community in the coastal North Sea during a spring phytoplankton bloom (2005)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 53 (2005), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The hydrophilic and hydrophobic properties of single cells of natural bacterioplankton communities were determined using a recently developed staining method combined with confocal laser scanning microscopy and advanced image analysis. On an average, about 50% of the bacterial cell area was covered by hydrophobic and only 16% by hydrophilic properties, while about 72% was covered by the genome. However, the size of these properties was independent of the bacterial cell size. Bacterial hydrophobicity was positively correlated with ambient 〈inlineGraphic alt="inline image" href="urn:x-wiley:01686496:FEM285:FEM_285_mu1" location="equation/FEM_285_mu1.gif"/〉 concentrations and negatively correlated with overall bacterial abundance. The expression of hydrophilicity was more dynamic. Over the spring phytoplankton bloom, the bacterioplankton ratiophil/phob repeatedly reached highest values shortly before peaks in bacterioplankton abundance were observed, indicating a direct and fast response of bacterial surface properties, especially hydrophilicity, to changing environmental conditions. Compared to bacterial strains, recently studied with the same method, cells of marine bacterioplankton communities are much smaller and less frequently covered by hydrophobic or hydrophilic properties. While the percentage area covered by the genome is essentially the same, the percentage area covered by hydrophobic or hydrophilic properties is much smaller.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/j.femsec.2005.01.015
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  • 4
    Electronic Resource
    Electronic Resource
    A comparison of DNA- and RNA-based clone libraries from the same marine bacterioplankton community (2005)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 51 (2005), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Clones from the same marine bacterioplankton community were sequenced, 100 clones based on DNA (16S rRNA genes) and 100 clones based on RNA (16S rRNA). This bacterioplankton community was dominated by α-Proteobacteria in terms of repetitive DNA clones (52%), but γ-Proteobacteria dominated in terms of repetitive RNA clones (44%). The combined analysis led to a characterization of phylotypes otherwise uncharacterized if only the DNA or RNA libraries would have been analyzed alone. Of the DNA clones, 25.5% were found only in this library and no close relatives were detected in the RNA library. For clones from the RNA library, 21.5% of RNA clones did not indicate close relatives in the DNA library. Based on the comparisons between DNA and RNA libraries, our data indicate that the characterization of the bacterial community based on RNA has the potential to characterize distinct phylotypes from the marine environment, which remain undetected on the DNA level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/j.femsec.2004.09.012
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  • 5
    Electronic Resource
    Electronic Resource
    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
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/j.femsec.2005.04.002
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  • 6
    Electronic Resource
    Electronic Resource
    Bacterial metabolism in the River Danube: parameters influencing bacterial production (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 34 (1995), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Microbial parameters were determined at five sampling sites in the River Danube up-and downstream of Vienna, Austria, twice monthly over an annual cycle. Bacterial production (BP) was estimated from thymidine and leucine incorporations; additionally, the effect of turbulence on BP and the conversion factors for converting incorporation rates into bacterial cell production were determined using the cumulative approach.2. BP under turbulent conditions was not significantly different from that under stagnant conditions. For thymidine, a mean annual conversion factor of 3.2 ± 1018 cells mol−1 thymidine incorporated was calculated. For leucine, the corresponding factor was 0.07 ± 1018 cells mol−1 leucine. Average annual BP calculated by thymidine incorporation was significantly higher than BP calculated from leucine incorporation and ranged from 47.2 to 77.5 μg C 1-−1 day−1 depending on the tracer and the conversion factor used.3. Bacterial growth rates ranged from 0.1 day−1 during winter to 1.7 day−1 in the summer. A strong correlation was found between temperature as well as chlorophyll a and bacterial growth when temperature was greater than 5 °C; a major spring phytoplankton bloom at a temperature below 5 °C did not increase BP.4. Dissolved organic carbon (DOC) concentrations varied between 2 and 7.2 mg C 1-−1 and comprised between 50 and 92% of the total organic carbon pool in the River Danube, Based on the DOC concentration and an assumed bacterial growth yield of 20% we calculated mean DOC turnover times of around 60 days in the winter and less than 8 days during the summer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1995.tb00916.x
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  • 7
    Electronic Resource
    Electronic Resource
    Allochthonous and autochthonous particulate organic matter in floodplains of the River Danube: the importance of hydrological connectivity (2003)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 48 (2003), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY 1. The elemental composition, the proportion of living organic carbon and the carbon stable isotope signatures of particulate organic matter (POM) were determined in a large river floodplain system in order to elucidate the major carbon sources in relation to the hydrological conditions over a 13-month period.2. Two floodplain segments and the main channel of the River Danube downstream of Vienna (Austria), were compared on the basis of discharge and water age estimations. The more dynamic floodplain was connected to the main channel for 46% of the study period and drained up to 12% of total discharge at high water.3. The mean C : N ratio and δ13C signature of the POM increased from the floodplain site that was more isolated from the river (6.6; −33‰) to the main channel (8.4; −25‰). At the dynamic floodplain site, the C : N ratio and the δ13C signature of the POM increased with hydrological connectivity (expressed as water age).4. Only during flood events (4% frequency of occurrence), a considerable input of riverine POM was observed. This input was indicated by a C : N ratio of the POM pool of more than 10, the amount of detrital carbon (〉80% of the total POM pool) and a δ13C signature of POM of more than −25‰ in the dynamic floodplain.5. Plankton derived carbon, indicated by C : N ratios less than eight and δ13C values lower than −25‰, dominated the particulate organic carbon (POC) pool at both floodplain sites, emphasising the importance of local (autochthonous) production. Phytoplankton was the major plankton compartment at the dynamic site, with highest biomasses at medium water ages.6. At the dynamic floodplain site, the Danube Restoration Project has enhanced the duration of upstream surface connection with the main channel from 4 to 46% frequency of occurrence. Therefore, the export of living POC to the main channel is now established during phases of maximum phytoplankton production and doubled the estimated total export of non-refractory POM compared with prerestoration conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2003.00981.x
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  • 8
    Electronic Resource
    Electronic Resource
    Seasonal and spatial distribution of dissolved and particulate organic carbon and bacteria in the bank of an impounding reservoir on the Enns River, Austria (2001)
    Oxford UK : Blackwell Science Ltd
    Freshwater biology 46 (2001), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Interstitial bacterial abundance, production and ectoenzyme activity were investigated over an annual cycle in an Austrian river when infiltration of oligotrophic river water into a river-bank was artificially enhanced. These microbial parameters were related to porewater chemistry and the concentration of particulate (POC) and dissolved organic carbon (DOC).2. Porewater chemistry reflected the hydrodynamic mixing of infiltrating river water with riparian groundwater. Seasonal fluctuations in the microbial parameters resulted mainly from changes in temperature and organic matter supply. Seasonal change in porewater chemistry in the river-bank was detectable laterally only within the first metre of the sediment and decreased rapidly with increasing distance from the sediment–water interface.3. The DOC concentration decreased only slightly during lateral transport through the aquifer, while total organic carbon (TOC) concentration as well as abundance and activity of interstitial bacteria were reduced by up to one order of magnitude within the top metre of the sediment. Retention of incoming particulate matter structured the lateral distribution pattern of TOC concentration. The POC and not the DOC pool was the main source of carbon for interstitial bacteria and, therefore, the quality of POC determines the distribution of microbial metabolism within the riparian zone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2001.00743.x
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  • 9
    Electronic Resource
    Electronic Resource
    Laboratory-made particles as a useful approach to analyse microbial processes in marine macroaggregates (1998)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 26 (1998), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Two kinds of particles were created in the laboratory in rolling tanks to simulate natural macroaggregates. Laboratory-made particles type 1 were formed under sterile conditions from a mixture of cells and extracellular products of four diatom species in artificial seawater, and inoculated with a marine microbial assemblage. Laboratory-made particles type 2 were created directly from natural seawater. These particles were characterised in terms of maximum length, volume and abundance. Chemical composition (carbohydrates, amino acids and total organic carbon) and bacterial and flagellate abundances were measured in the particles and ambient water. We found that both kinds of laboratory-made particles were similar in terms of size, chemical composition and microbial abundance. Moreover, they resembled natural marine aggregates in size and volume. However, laboratory-made particles showed higher concentrations of carbohydrates, amino acids and total organic carbon as well as higher microbial abundance when compared to natural macroaggregates. This difference can be explained by the sampling method, since natural aggregates are frequently collected in the sea with syringes including ambient water, and consequently diluted, whereas in this study the laboratory-made particles were carefully collected without ambient water. Thus, both kinds of laboratory-made particles might be a good alternative for the analysis of microbial processes in marine macroaggregates. Advantages and disadvantages of these two types of laboratory-made particles are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1998.tb00517.x
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  • 10
    Electronic Resource
    Electronic Resource
    Major role of ultraviolet-B in controlling bacterioplankton growth in the surface layer of the ocean (1993)
    [s.l.] : Nature Publishing Group
    Nature 361 (1993), S. 717-719 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In evaluating the possible effects of natural solar radiation, we have to distinguish possible effects of short- and long-term exposure on the bacterial community. In a mixed water column, short-term exposure should predominate. We determined the influence of short-term (30 min) solar radiation on ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/361717a0
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