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  • 11
    Language: English
    In: Chemical Engineering & Technology, June 2017, Vol.40(6), pp.1107-1114
    Description: Time‐dependent effects on the apparent roughness and surface free energy of different polymeric surfaces and stainless steel were studied during the biofouling process for K12. The surface roughness increases during primary adhesion of on the surfaces and is later reduced as the surface between scattered bacteria is completely covered, forming a uniform biofilm. During the fouling process, the polar fraction of the surface free energy significantly increased, whereas the dispersive fraction decreased for all substrates. The attachment of and subsequent bacterial production of extracellular polymeric substances increased the polarity of the initially nonpolar polymeric surfaces to increase wettability. Surfaces of polymeric heat exchangers show beneficial biofouling tendencies, compared with those of stainless steel, in applications utilizing river water as a coolant. The measurable surface characteristics of the biofilm change drastically over time and have to be considered in fluid simulations. Correlations between initial roughness and wettability are given with respect to biofilm formation.
    Keywords: Adhesion ; Biofouling ; Heat Exchangers ; Polymers ; Surface Properties
    ISSN: 0930-7516
    E-ISSN: 1521-4125
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  • 12
    Language: English
    In: Research and Reports in Biology, 2018, Vol.9, p.1(16)
    Description: Biofilms constitute an important issue in microbial ecology, due to their high ecological and economic relevance, but the impact of abiotic conditions and microbial key players on the development and functionality of a natural biofilm is still little understood. This study investigated the effects of light intensity (LI) and bed shear stress (BSS) and the role of dominant microbes during the formation of natural biofilms and particularly the process microbial biostabilization. A comprehensive analysis of microbial biomass, extracellular polymeric substances produced, and the identification of dominant bacterial and algal species was correlated with assessment of biofilm adhesiveness/stability. LI and BSS impacted the biofilms in very different ways: biofilm adhesiveness significantly increased with LI and decreased with BSS. Moreover, microbial biomass and the functional organization of the bacterial community increased with LI, while the dynamics in the bacterial community increased with BSS. Most stable biofilms were dominated by sessile diatoms like Achnanthidium minutissimum or Fragilaria pararumpens and bacteria with either filamentous morphology, such as Pseudanabaena biceps, or a potential high capacity for extracellular polymeric-substance production, such as Rubrivivax gelatinosus. In contrast, microbes with high motility, such as Nitzschia fonticola, Pseudomonas fluorescens, and Caulobacter vibrioides, dominated the least adhesive biofilms. Their movement and potential antibiotic production could have had a disruptive impact on the biofilm matrix, which decreased its stability. This is the first study to unveil the link between abiotic conditions and resulting shifts in key microbial players to impact the ecosystem-service microbial biostabilization. Keywords: microbial biostabilization, natural biofilms, abiotic factors, microbial community, mesocosm
    Keywords: Ecosystem Components – Analysis
    ISSN: 1179-7274
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  • 13
    Language: English
    In: Vakuum in Forschung und Praxis, April-May, 2014, Vol.26(2), p.42(6)
    Keywords: Atomic Force Microscopy
    ISSN: 0947-076X
    Source: Cengage Learning, Inc.
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  • 14
    In: Applied and Environmental Microbiology, 1998, Vol. 64(2), p.496
    Description: A bacterial mixed culture reductively dechlorinating trichlorobenzenes was established in a defined, synthetic mineral medium without any complex additions and with pyruvate as the carbon and energy source. The culture was maintained over 39 consecutive transfers of small inocula into fresh media, enriching the dechlorinating activity. In situ probing with fluorescence-labeled rRNA-targeted oligonucleotide probes revealed that two major subpopulations within the microbial consortium were phylogenetically affiliated with a sublineage within the Desulfovibrionaceae and the gamma subclass of Proteobacteria. The bacterial consortium grew by fermentation of pyruvate, forming acetate, propionate, CO2, formate, and hydrogen. Acetate and propionate supported neither the reduction of trichlorobenzenes nor the reduction of sulfate when sulfate was present. Hydrogen and formate were used for sulfate reduction to sulfide. Sulfate strongly inhibited the reductive dechlorination of trichlorobenzenes. However, when sulfate was depleted in the medium due to sulfate reduction, dechlorination of trichlorobenzenes started. Similar results were obtained when sulfite was present in the cultures. Molybdate at a concentration of 1 mM strongly inhibited the dechlorination of trichlorobenzenes. Cultures supplied with molybdate plus sulfate did not reduce sulfate, but dechlorination of trichlorobenzenes occurred. Supplementation of electron-depleted cultures with various electron sources demonstrated that formate was used as a direct electron donor for reductive dechlorination, whereas hydrogen was not.
    Keywords: Bacteria -- Metabolism ; Chlorobenzenes -- Metabolism;
    ISSN: 0099-2240
    ISSN: 00992240
    E-ISSN: 10985336
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  • 15
    Language: English
    In: Journal of Plant Nutrition and Soil Science, October 2017, Vol.180(5), pp.602-613
    Description: Silver nanoparticles (AgNP) are used in a broad range of consumer products and industrial applications. During the regular product life cycle and disposal, AgNP are continuously released into the environment. Hence, the aim of this study was to investigate the potential ecotoxicological effects of AgNP exposure on amoebae. The ATCC 30234 strain and environmental isolate strain C5/2, which are both affiliated with genotype T4, were chosen as representatives of ecologically important soil protozoan organisms. The amoebae were exposed to citrate‐stabilized AgNP (30 and 70 nm in size) for 24 h and 96 h at concentrations ranging from 600 µg L to 20 mg L. A newly adopted cell culture based microscopic assay was applied to assess the adherence ability of the amoeba trophozoites. The general metabolic activity of was determined to be a second independent endpoint by means of intracellular reduction of the redox dye AlamarBlue®. The fate of AgNP within the amoebae and test solutions was visualized by light‐ and transmission electron microscopy (TEM). Both strains showed a significant dose‐dependent decrease of adherence ability ( 〈 0.04) and metabolic activity ( 〈 0.01) after 96 h of AgNP exposure. The environmental strain C5/2 lost both its adherence ability and metabolic activity at lower AgNP concentrations than the type strain, indicating a higher sensitivity to ionic silver. This was confirmed by the application of AgNO, provoking a higher effect level in strain C5/2. AgNP was visualized intracellularly by transmission electron microscopy within the cytoplasm of . This is the first report to show the ecotoxicological effects of short‐term AgNP exposure on the soil protist , causing both changes in the adherence ability and metabolic activity of this amoeba. This combined approach may be a powerful tool in the future for predicting potential harmful ecotoxicological effects of AgNP exposure using soil protozoans.
    Keywords: Acanthamoeba ; Adherence ; Metabolic Activity ; Silver Nanoparticles ; Soil Microbial Food Web ; Top Predator
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 16
    Language: English
    In: Ecological Indicators, August 2012, Vol.19, pp.118-129
    Description: Indices to assess the ecological status of water bodies according to the European Water Framework Directive (WFD) frequently produce widely differing results when applied to estuarine systems. Although several ecological indices have been employed to coastal environments and in estuaries in particular, there is still a lack of knowledge about their suitability for assessing the ecological status of heavily modified water bodies. Thus, we evaluated the performances of indices and fauna parameters (AMBI, M-AMBI, BOPA, BO2A, -value, Shannon diversity, species richness, abundance) that have been discussed in the WFD context using data on invertebrates dwelling in two typical morphological units: the navigation channel and the river bank habitats of Elbe estuary (Germany). In addition, we tested their ability to identify several environmental factors (grain size distribution and chemical sediment contamination). All indices were able to detect major changes in macrofauna composition along the estuarine salinity gradient and were able to differentiate between navigation channel and shallow bank habitats. A strong significant correlation was found with most indices with the exceptions of the -value and the BOPA with mean grain size. Almost all indices signaled poor ecological quality in the coarser fairway sediments against the finer sublitoral bank sediments. However, AMBI and BOPA showed the opposite: both indicators classified the invertebrate assemblages from the navigation channel better compare than the shallower habitats. The correlation of ecological indices and parameters with sediment contaminants and the toxicity of the sediment calculated as toxic units showed a diverse picture: all indices, except species richness and the BOPA, had a certain significant correlation with several individual sediment pollutants, however, only one index, the -value, was correlated significant with the majority of chemical pollutants (Pb, Cd, Cu, Ni, Hg, Zn, β-HCH, pp′-DDD, and TBT) and the toxic units. Our results show clearly that ecological quality classification of heavily modified estuaries depends strongly on both the index and the habitat. Thus, we conclude that no index should be used on its own to estimate the ecological quality of estuaries. Further investigations and the improvement or development of such indices should place emphasis on their independence from the grain size spectrum of the sediments and on their good correlation with its pollution status.
    Keywords: Sediment Contamination ; Water Framework Directive ; Benthic Indicators ; W-Statistic ; Bopa ; Bo2a ; Ambi ; M-Ambi ; Environmental Sciences
    ISSN: 1470-160X
    E-ISSN: 1872-7034
    Source: ScienceDirect Journals (Elsevier)
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  • 17
    Language: English
    In: Environmental Science and Pollution Research, 2016, Vol.23(23), pp.24277-24288
    Description: Bacterial biofilms are most likely confronted with silver nanoparticles (Ag NPs) as a pollutant stressor in aquatic systems. In this study, biofilms of Aquabacterium citratiphilum were exposed for 20 h to 30 and 70 nm citrate stabilized Ag NPs in low-dose concentrations ranging from 600 to 2400 μg l −1 , and the Ag NP-mediated effects on descriptive, structural, and functional biofilm characteristics, including viability, protein content, architecture, and mechanical stability, were investigated. Viability, based on the bacterial cell membrane integrity of A. citratiphilum , as determined by epifluorescence microscopy, remained unaffected after Ag NP exposure. Moreover, in contrast to information in the current literature, protein contents of cells and extracellular polymeric substances (EPS) and biofilm architecture, including dry mass, thickness, and density, were not significantly impacted by exposure to Ag NPs. However, the biofilms themselves served as effective sinks for Ag NPs, exhibiting enrichment factors from 5 to 8. Biofilms showed a greater capacity to accumulate 30 nm sized Ag NPs than 70 nm Ag NPs. Furthermore, Ag NPs significantly threatened the mechanical stability of biofilms, as determined by a newly developed assay. For 30 nm Ag NPs, the mechanical stability of biofilms decreased as the Ag NP concentrations applied to them increased. In contrast, 70 nm Ag NPs produced a similar decrease in mechanical stability for each applied concentration. Overall, this finding demonstrates that exposure to Ag NPs triggers remarkable changes in biofilm adhesion and/or cohesiveness. Because of biofilm-mediated ecological services, this response raises environmental concerns regarding Ag NP release into freshwater systems, even in sublethal concentrations.
    Keywords: Aquabacterium citratiphilum ; biofilm ; Silver nanoparticles ; Toxicity ; Mechanical stability ; Nanoparticle enrichment
    ISSN: 0944-1344
    E-ISSN: 1614-7499
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  • 18
    Language: English
    In: Environmental Science and Pollution Research, 9/20/2016
    ISSN: 0944-1344
    E-ISSN: 1614-7499
    Source: Springer (via CrossRef)
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  • 19
    Language: English
    In: Ecological indicators, 2012, Vol.19, pp.118-129
    Description: Indices to assess the ecological status of water bodies according to the European Water Framework Directive (WFD) frequently produce widely differing results when applied to estuarine systems. Although several ecological indices have been employed to coastal environments and in estuaries in particular, there is still a lack of knowledge about their suitability for assessing the ecological status of heavily modified water bodies. Thus, we evaluated the performances of indices and fauna parameters (AMBI, M-AMBI, BOPA, BO2A, W-value, Shannon diversity, species richness, abundance) that have been discussed in the WFD context using data on invertebrates dwelling in two typical morphological units: the navigation channel and the river bank habitats of Elbe estuary (Germany). In addition, we tested their ability to identify several environmental factors (grain size distribution and chemical sediment contamination). All indices were able to detect major changes in macrofauna composition along the estuarine salinity gradient and were able to differentiate between navigation channel and shallow bank habitats. A strong significant correlation was found with most indices with the exceptions of the W-value and the BOPA with mean grain size. Almost all indices signaled poor ecological quality in the coarser fairway sediments against the finer sublitoral bank sediments. However, AMBI and BOPA showed the opposite: both indicators classified the invertebrate assemblages from the navigation channel better compare than the shallower habitats. The correlation of ecological indices and parameters with sediment contaminants and the toxicity of the sediment calculated as toxic units showed a diverse picture: all indices, except species richness and the BOPA, had a certain significant correlation with several individual sediment pollutants, however, only one index, the W-value, was correlated significant with the majority of chemical pollutants (Pb, Cd, Cu, Ni, Hg, Zn, β-HCH, pp′-DDD, and TBT) and the toxic units. Our results show clearly that ecological quality classification of heavily modified estuaries depends strongly on both the index and the habitat. Thus, we conclude that no index should be used on its own to estimate the ecological quality of estuaries. Further investigations and the improvement or development of such indices should place emphasis on their independence from the grain size spectrum of the sediments and on their good correlation with its pollution status. ; p. 118-129.
    Keywords: Zinc ; Environmental Factors ; Habitats ; Hch (Pesticide) ; Copper ; Fauna ; Pollutants ; Surface Water ; Lead ; Salinity ; Invertebrates ; Sediment Contamination ; Estuaries ; Toxicity ; Sediments ; Cadmium ; Nickel ; Species Diversity ; Mercury
    ISSN: 1470-160X
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 20
    In: Applied and Environmental Microbiology, Nov, 1997, Vol.63(11), p.4164(7)
    Description: The dominant bacterial populations in drinking water biofilms in a municipal drinking water distribution system in Berlin, Germany, are identified. Specific oligonucleotide probes were employed in the in situ investigations. Dominant bacterial species were isolated and characterized phylogenetically. In situ probing of bacteria in their natural environment will provide information regarding phylogenetic identity and in situ distribution correlation.
    Keywords: Drinking Water -- Contamination ; Bacteria -- Identification And Classification
    ISSN: 0099-2240
    E-ISSN: 10985336
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