| 11. |
- Heinicke, G., et al.
(författare)
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The effect of biological pre-filtration on the performance of conventional surface water treatment
- 2006
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Ingår i: Journal of Water Supply: Research and Technology - Aqua. - 0003-7214. ; 55:2, s. 109-119
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Tidskriftsartikel (refereegranskat)abstract
- Many waterworks that apply conventional treatment of surface water, by flocculation and filtration, have to deal with seasonal changes of the raw water quality, increasing concentrations of natural organic matter (NOM), and the necessity to improve particle removal. A pilot plant was operated to closely resemble the full-scale treatment at a surface water treatment plant in Göteborg, Sweden. Treatment consisted of flocculation, sedimentation and rapid granular activated carbon (GAC) filtration. To assess the effects of biological pre-filtration, the feed water to the pilot plant was switched weekly between surface water and biofiltered water which had passed through adsorptively exhausted GAC at an empty bed contact time (EBCT) of 34 minutes. The processes were investigated with regard to NOM, the bacterial re-growth potential, as well as their function as a barrier for suspended particles that originate from the raw water. Biological pre-filtration improved particle removal and made it less dependent on the post-sedimentation GAC rapid filter, thereby improving robustness. Episodically elevated concentrations of earthy-musty odour compounds, which are not reliably removed by flocculation and filtration, were reduced by the biofilters. The process combination may be of particular interest for waterworks with variable raw water quality.
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| 12. |
- Kämpfer, P, et al.
(författare)
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Undibacterium pigrum gen. nov., sp. nov., isolated from drinking water
- 2007
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Ingår i: International Journal of Systematic and Evolutionary Microbiology. - : Microbiology Society. - 1466-5026 .- 1466-5034. ; 57:7, s. 1510-1515
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Tidskriftsartikel (refereegranskat)abstract
- Two Gram-negative, rod-shaped, oxidase-positive, non-spore-forming, non-motile bacteria (strains CCUG 49009T and CCUG 49012), both isolated from drinking water, were characterized. On the basis of chemotaxonomic data [major ubiquinone, Q-8; predominant polyamines, putrescine and 2-hydroxyputrescine; major polar lipids, phosphatidylethanolamine, moderate amounts of diphosphatidylglycerol and phosphatidylglycerol and minor amounts of three aminolipids and phosphatidylserine; major fatty acids, C16:0 and summed feature 3 (C16:1ω7c/C15:0 iso 2-OH)] and 16S rRNA gene sequence similarities, both strains clearly belong to the family Oxalobacteraceae of the Betaproteobacteria. 16S rRNA gene sequence similarities with members of the most closely related genera of this group (Herminiimonas, Massilia, Duganella, Telluria, Herbaspirillum, Janthinobacterium, Naxibacter and Paucimonas) were less than 96.5% for both strains. The two strains also shared a relatively low 16S rRNA gene sequence similarity (96.8%). Although phylogenetic analysis based on 16S rRNA gene sequence similarities clearly showed that the two organisms formed a separate branch, their phenotypes (including chemotaxonomic features) were hardly distinguishable and showed high similarities to those reported for the most closely related genera. On the basis of DNA–DNA hybridization results, the two strains were shown to represent separate species (sharing only 20% DNA–DNA relatedness), but they could not be clearly differentiated phenotypically from each other. It is evident that these organisms represent a new genus, Undibacterium gen. nov., with one species, Undibacterium pigrum sp. nov. The type strain of Undibacterium pigrum is strain CCUG 49009T (=CIP 109318T). Strain CCUG 49012 (=CIP 108976) probably represents a second species of this genus, but is described here as a second genomovar of this species because of the lack of differentiating characters.
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| 13. |
- Liebana, Raquel, 1986, et al.
(författare)
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Combined Deterministic and Stochastic Processes Control Microbial Succession in Replicate Granular Biofilm Reactors
- 2019
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Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 53:9, s. 4912-4921
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Tidskriftsartikel (refereegranskat)abstract
- Granular sludge is an efficient and compact biofilm process for wastewater treatment. However, the ecological factors involved in microbial community assembly during the granular biofilm formation are poorly understood, and little is known about the reproducibility of the process. Here, three replicate bioreactors were used to investigate microbial succession during the formation of granular biofilms. We identified three successional phases. During the initial phase, the successional turnover was high and alpha-diversity decreased as a result of the selection of taxa adapted to grow on acetate and form aggregates. Despite these dynamic changes, the microbial communities in the replicate reactors were similar. The second successional phase occurred when the settling time was rapidly decreased to selectively retain granules in the reactors. The influence of stochasticity on succession increased and new niches were created as granules emerged, resulting in temporarily increased alpha-diversity. The third successional phase occurred when the settling time was kept stable and granules dominated the biomass. Turnover was low, and selection resulted in the same abundant taxa in the reactors, but drift, which mostly affected low-abundant community members, caused the community in one reactor to diverge from the other two. Even so, performance was stable and similar between reactors.
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| 14. |
- Liebana, Raquel, 1986, et al.
(författare)
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Resistance of aerobic granular sludge microbiomes to periodic loss of biomass
- 2023
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Ingår i: Biofilm. - 2590-2075. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Granular sludge is a biofilm process used for wastewater treatment which is currently being implemented worldwide. It is important to understand how disturbances affect the microbial community and performance of reactors. Here, two acetate-fed replicate reactors were inoculated with acclimatized sludge and the reactor performance, and the granular sludge microbial community succession were studied for 149 days. During this time, the microbial community was challenged by periodically removing half of the reactor biomass, subsequently increasing the food-to-microorganism (F/M) ratio. Diversity analysis together with null models show that overall, the microbial communities were resistant to the disturbances, observing some minor effects on polyphosphate-accumulating and denitrifying microbial communities and their associated reactor functions. Community turnover was driven by drift and random granule loss, and stochasticity was the governing ecological process for community assembly. These results evidence the aerobic granular sludge process as a robust system for wastewater treatment.
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| 15. |
- Lundgren, Anders, 1978, et al.
(författare)
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Gold-nanoparticle-assisted self-assembly of chemical gradients with tunable sub-50 nm molecular domains
- 2014
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Ingår i: Particle & particle systems characterization. - : Wiley. - 0934-0866 .- 1521-4117. ; 31:2, s. 209-218
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Tidskriftsartikel (refereegranskat)abstract
- A simple and efficient principle for nanopatterning with wide applicability in the sub-50 nanometer regime is chemisorption of nanoparticles; at homogeneous substrates, particles carrying surface charge may spontaneously self-organize due to the electrostatic repulsion between adjacent particles. Guided by this principle, a method is presented to design, self-assemble, and chemically functionalize gradient nanopatterns where the size of molecular domains can be tuned to match the level corresponding to single protein binding events. To modulate the binding of negatively charged gold nanoparticles both locally (<100 nm) and globally (>100 μm) onto a single modified gold substrate, ion diffusion is used to achieve spatial control of the particles' mutual electrostatic interactions. By subsequent tailoring of different molecules to surface-immobilized particles and the void areas surrounding them, nanopatterns are obtained with variable chemical domains along the gradient surface. Fimbriated Escherichia coli bacteria are bound to gradient nanopatterns with similar molecular composition and macroscopic contact angle, but different sizes of nanoscopic presentation of adhesive (hydrophobic) and repellent poly(ethylene) glycol (PEG) domains. It is shown that small hydrophobic domains, similar in size to the diameter of the bacterial fimbriae, supported firmly attached bacteria resembling catch-bond binding, whereas a high number of loosely adhered bacteria are observed on larger hydrophobic domains. Chemical gradients with the resolution needed to address complex biological binding events at the single protein level are prepared using surface-deposited gold nanoparticles as a versatile template for orthogonal chemical modifications. The effect of hydrophobic domain arrangement on the sub-50 nm scale is shown to influence binding of fimbriae carrying E. coli bacteria. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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| 16. |
- Modin, Oskar, 1980, et al.
(författare)
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Hill-based dissimilarity indices and null models for analysis of microbial community assembly
- 2020
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Ingår i: Microbiome. - : Springer Science and Business Media LLC. - 2049-2618. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundHigh-throughput amplicon sequencing of marker genes, such as the 16S rRNA gene in Bacteria and Archaea, provides a wealth of information about the composition of microbial communities. To quantify differences between samples and draw conclusions about factors affecting community assembly, dissimilarity indices are typically used. However, results are subject to several biases, and data interpretation can be challenging. The Jaccard and Bray-Curtis indices, which are often used to quantify taxonomic dissimilarity, are not necessarily the most logical choices. Instead, we argue that Hill-based indices, which make it possible to systematically investigate the impact of relative abundance on dissimilarity, should be used for robust analysis of data. In combination with a null model, mechanisms of microbial community assembly can be analyzed. Here, we also introduce a new software, qdiv, which enables rapid calculations of Hill-based dissimilarity indices in combination with null models.ResultsUsing amplicon sequencing data from two experimental systems, aerobic granular sludge (AGS) reactors and microbial fuel cells (MFC), we show that the choice of dissimilarity index can have considerable impact on results and conclusions. High dissimilarity between replicates because of random sampling effects make incidence-based indices less suited for identifying differences between groups of samples. Determining a consensus table based on count tables generated with different bioinformatic pipelines reduced the number of low-abundant, potentially spurious amplicon sequence variants (ASVs) in the data sets, which led to lower dissimilarity between replicates. Analysis with a combination of Hill-based indices and a null model allowed us to show that different ecological mechanisms acted on different fractions of the microbial communities in the experimental systems.ConclusionsHill-based indices provide a rational framework for analysis of dissimilarity between microbial community samples. In combination with a null model, the effects of deterministic and stochastic community assembly factors on taxa of different relative abundances can be systematically investigated. Calculations of Hill-based dissimilarity indices in combination with a null model can be done in qdiv, which is freely available as a Python package (https://github.com/omvatten/qdiv). In qdiv, a consensus table can also be determined from several count tables generated with different bioinformatic pipelines.
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| 17. |
- Modin, Oskar, 1980, et al.
(författare)
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Nonoxidative removal of organics in the activated sludge process
- 2016
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Ingår i: Critical Reviews in Environmental Science and Technology. - : Informa UK Limited. - 1064-3389 .- 1547-6537. ; 46:7, s. 635-672
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Tidskriftsartikel (refereegranskat)abstract
- The activated sludge process is commonly used to treat wastewater by aerobic oxidation of organic pollutants into carbon dioxide and water. However, several nonoxidative mechanisms can also contribute to removal of organics. Sorption onto activated sludge can remove a large fraction of the colloidal and particulate wastewater organics. Intracellular storage of, e.g., polyhydroxyalkanoates (PHA), triacylglycerides (TAG), or wax esters can convert wastewater organics into precursors for high-value products. Recently, several environmental, economic, and technological drivers have stimulated research on nonoxidative removal of organics for wastewater treatment. In this paper, we review these nonoxidative removal mechanisms as well as the existing and emerging process configurations that make use of them for wastewater treatment. Better utilization of nonoxidative processes in activated sludge could reduce the wasteful aerobic oxidation of organic compounds and lead to more resource-efficient wastewater treatment plants.
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| 18. |
- Norberg, Peter, 1974, et al.
(författare)
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The IncP-1 plasmid backbone adapts to different host bacterial species and evolves through homologous recombination.
- 2011
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Ingår i: Nature communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 2
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Tidskriftsartikel (refereegranskat)abstract
- Plasmids are important members of the bacterial mobile gene pool, and are among the most important contributors to horizontal gene transfer between bacteria. They typically harbour a wide spectrum of host beneficial traits, such as antibiotic resistance, inserted into their backbones. Although these inserted elements have drawn considerable interest, evolutionary information about the plasmid backbones, which encode plasmid related traits, is sparse. Here we analyse 25 complete backbone genomes from the broad-host-range IncP-1 plasmid family. Phylogenetic analysis reveals seven clades, in which two plasmids that we isolated from a marine biofilm represent a novel clade. We also found that homologous recombination is a prominent feature of the plasmid backbone evolution. Analysis of genomic signatures indicates that the plasmids have adapted to different host bacterial species. Globally circulating IncP-1 plasmids hence contain mosaic structures of segments derived from several parental plasmids that have evolved in, and adapted to, different, phylogenetically very distant host bacterial species.
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| 19. |
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| 20. |
- Nylund, Göran M., 1974, et al.
(författare)
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Seaweed defence against bacteria: a poly-brominated 2-heptanone from the red alga Bonnemaisonia hamifera inhibits bacterial colonisation
- 2008
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 369, s. 39-50
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Tidskriftsartikel (refereegranskat)abstract
- It has previously been shown that the red alga Bonnemaisonia hamifera is less fouled by bacteria relative to co-occurring seaweeds and that surface extracts of B. hamifera inhibit bacterial growth at natural concentrations. In the present study, we isolated the antibacterial metabolite by bioassay-guided fractionation of extracts of B. hamifera using standard chromatographic methods. Nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry were used for molecular identification. The antibacterial activity in the extracts was caused by a previously described poly-halogenated 2-heptanone: 1,1,3,3-tetrabromo-2-heptanone. To further investigate the role of this compound as an ecologically relevant antifoulant against bacterial colonisation, we quantified it on the surface of B. hamifera specimens collected in the field. Levels of 1,1,3,3-tetrabromo-2-heptanone on the surface of the algae were on average 3.6 µg cm–2. Natural surface concentrations of this secondary metabolite were used to test for growth-inhibiting effects against 18 bacterial strains isolated from red algae co-occurring with B. hamifera. The test indicated a phylogenetic specificity of the metabolite, and gram-positive bacteria and flavobacteria proved to be particularly sensitive. In a further test, natural surface concentrations of 1,1,3,3-tetrabromo-2-heptanone were applied to artificial panels and incubated in the sea. After 4 and 7 d, the number of settled bacteria was significantly lower on all treated panels compared to controls. Thus, this study shows that 1,1,3,3-tetrabromo-2-heptanone has an ecologically relevant role as an antifoulant against bacterial colonisation on the surface of B. hamifera. This study is also one of only a few to quantify natural surface concentrations of a seaweed secondary metabolite.
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