| 1. |
- Berglund, Eva C., et al.
(författare)
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Genome dynamics of Bartonella grahamii in micro-populations of woodland rodents
- 2010
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Ingår i: BMC Genomics. - : Springer Science and Business Media LLC. - 1471-2164. ; 11, s. 152-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Rodents represent a high-risk reservoir for the emergence of new human pathogens. The recent completion of the 2.3 Mb genome of Bartonella grahamii, one of the most prevalent blood-borne bacteria in wild rodents, revealed a higher abundance of genes for host-cell interaction systems than in the genomes of closely related human pathogens. The sequence variability within the global B. grahamii population was recently investigated by multi locus sequence typing, but no study on the variability of putative host-cell interaction systems has been performed. Results: To study the population dynamics of B. grahamii, we analyzed the genomic diversity on a whole-genome scale of 27 B. grahamii strains isolated from four different species of wild rodents in three geographic locations separated by less than 30 km. Even using highly variable spacer regions, only 3 sequence types were identified. This low sequence diversity contrasted with a high variability in genome content. Microarray comparative genome hybridizations identified genes for outer surface proteins, including a repeated region containing the fha gene for filamentous hemaggluttinin and a plasmid that encodes a type IV secretion system, as the most variable. The estimated generation times in liquid culture medium for a subset of strains ranged from 5 to 22 hours, but did not correlate with sequence type or presence/absence patterns of the fha gene or the plasmid. Conclusion: Our study has revealed a geographic microstructure of B. grahamii in wild rodents. Despite near-identity in nucleotide sequence, major differences were observed in gene presence/absence patterns that did not segregate with host species. This suggests that genetically similar strains can infect a range of different hosts.
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| 2. |
- Berglund, Eva C., et al.
(författare)
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Run-off replication of host-adaptability genes is associated with gene transfer agents in the genome of mouse-infecting Bartonella grahamii
- 2009
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Ingår i: PLoS genetics. - : Public Library of Science (PLoS). - 1553-7404. ; 5:7, s. e1000546-
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Tidskriftsartikel (refereegranskat)abstract
- The genus Bartonella comprises facultative intracellular bacteria adapted to mammals, including previously recognized and emerging human pathogens. We report the 2,341,328 bp genome sequence of Bartonella grahamii, one of the most prevalent Bartonella species in wild rodents. Comparative genomics revealed that rodent-associated Bartonella species have higher copy numbers of genes for putative host-adaptability factors than the related human-specific pathogens. Many of these gene clusters are located in a highly dynamic region of 461 kb. Using hybridization to a microarray designed for the B. grahamii genome, we observed a massive, putatively phage-derived run-off replication of this region. We also identified a novel gene transfer agent, which packages the bacterial genome, with an over-representation of the amplified DNA, in 14 kb pieces. This is the first observation associating the products of run-off replication with a gene transfer agent. Because of the high concentration of gene clusters for host-adaptation proteins in the amplified region, and since the genes encoding the gene transfer agent and the phage origin are well conserved in Bartonella, we hypothesize that these systems are driven by selection. We propose that the coupling of run-off replication with gene transfer agents promotes diversification and rapid spread of host-adaptability factors, facilitating host shifts in Bartonella.
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| 3. |
- Cheng, J., et al.
(författare)
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One-pot synthesis of porous gold nanoparticles by preparation of Ag/Au nanoparticles followed by dealloying
- 2013
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 1873-4359 .- 0927-7757. ; 436, s. 823-829
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Tidskriftsartikel (refereegranskat)abstract
- Porous gold nanoparticles were obtained from nanoparticle alloys of gold and silver. The alloy nanoparticles were prepared by reducing the gold and silver precursors, HAuCl4 and AgNO3, respectively with NaBH4. The reduction was made in a microemulsion of water-in-oil type and the precursors were contained in the water droplets. The droplet size of the microemulsion was 25-30 nm and the size of the mixed nanoparticles was 5-7 nm. The position of the plasmon band in the absorption spectrum, as well as analysis by energy-dispersive X-ray spectroscopy linked to high resolution scanning transmission electron microscopy showed that the nanoparticles were true alloys, not of core-shell type. The mixed nanoparticles were subsequently dealloyed by treatment with nitric acid, which dissolved silver much more readily than gold.
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| 4. |
- Holmberg, Anna, 1974, et al.
(författare)
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Does waterborne citalopram affect the aggressive and sexual behaviour of rainbow trout and guppy?
- 2011
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Ingår i: Journal of hazardous materials. - : Elsevier BV. - 1873-3336 .- 0304-3894. ; 187:1-3, s. 596-9
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Tidskriftsartikel (refereegranskat)abstract
- Citalopram is one of several selective serotonin reuptake inhibitors (SSRIs) commonly found in treated sewage effluents. Accordingly, there are concerns about possible adverse effects of SSRIs on aquatic organisms, particularly behavioural effects similar to those associated with SSRI use in humans. Rainbow trout fry and adult male guppies were therefore exposed to waterborne citalopram, ranging from environmentally relevant to high concentrations (1, 10, 100 μg/L) for 3-7 days. Under these experimental conditions citalopram does not appear to cause significant effects on aggression in rainbow trout fry or on sexual behaviour in male guppies. This may be explained by a relatively low uptake of citalopram from water to fish.
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| 5. |
- Holmberg, Johan, et al.
(författare)
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Old Moving Groups
- 2002
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Ingår i: Modes of Star Formation and the Origin of Field Populations, ASP Conference Proceedings.. - 1583811281 ; 285, s. 188-194
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Konferensbidrag (refereegranskat)
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| 6. |
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| 7. |
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| 8. |
- Lingdell, Pär-Erik, et al.
(författare)
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Dagsländan Siphlonurus armatus. Bidrag till kunskapen om den rödlistade dagsländan
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Den här rapporten har upprättats på uppdrag av Länsstyrelsen i Stockholms län. Rapportens huvudsyfte är att tjäna som underlag vid upprättandet av ett åtgärdsprogram för den rödlistade dagsländan Siphlonurus armatus Eaton, 1870 hotkategori NT (missgynnad). S. armatus påträffades i Skåne i början 1900-talet. Därefter saknas fynduppgifter fram till 1989 då arten påträffades i Stockholms län. Artens förekomst har sedan 1917 bara bekräftats i mer eller mindre temporärabäckar i Stockholms län. Ett betydande mörkertal avseende artens förekomst i Sverige kan föreligga. De svenska populationerna är de nordligast kända i världen.Arten i fråga har diskret brunmelerade synnerligen snabbsimmande larver som kan bli upp till 17 mm långa exklusive stjärtspröt. Arten förmodas övervintra som äggoch ha en snabb tillväxt under februari-mars till maj-juni då den kläcks. Rapporten grundar sig främst på data från Siphlonurus armatus-projektet som omfattar åtta lokaler i fyra vattendrag nära Tyresta nationalpark. I lokalerna harhabitatstruktur, kemi, vattentemperatur och bottenfauna registrerats under den första halvan av år 2006 i syfte att närmare ringa in artens habitatkrav. Data från åtta lokalerna har så långt möjligt analyserats mot cirka 10 000 bottenfaunaprov Limnodatas databas. I rapporten beskrivs de biotoper samt de kemiska och temperaturmässiga ramar inom vilka S. armatus har påträffats samt vad som kännetecknar biotoper där arten ej påträffats. Utifrån detta diskuteras sedan vilka hot som kan föreligga avseende artens fortsatta existens inom Sverige samt hur rådande kunskapsbrist skall kunna minskas. Följande resultat framkom:Svenska vattendrag där Siphlonurus armatus påträffatsTabell 1. Svenska vattendrag där Siphlonurus armatus påträffats efter år 1917. Koordinaterna avser,med undantag för Albysjön och Snävingen, utloppsområden i Östersjön. Samtliga vattendrag ligger iStockholms län.Vattendrag Utloppsområde Kommun X-koordinat Y-koordinatHusbyån Blista fjärd Haninge 6555950 1637185Lännåkersbäcken Lännåkersviken Haninge 6557515 1639070Rudabäcken Drevviken Haninge 6565745 1633840Träskbäcken Landfjärden Haninge 6549070 1626445Vinåkersbäcken Vinåkersviken Haninge 6562410 1647725Bergshamraån Snävingen Norrtälje 6614215 1648835Mjölstabäcken Skedviken Norrtälje 6632285 1639065Brakmarsbäcken Brakmaren (Storängsfladen) Tyresö 6567780 1643545Grändalssjöbäcken Albysjön Tyresö 6569220 1641375Mörkdalsbäcken Brakmaren (Storängsfladen) Tyresö 6567625 1644015Stormyrabäcken Brakmaren (Storängsfladen) Tyresö 6567590 1644015Vissvassdalsbäcken Vissvassfjärden Tyresö 6565710 1646950Åvaån. Bäck till. Åvaviken Tyresö 6563650 1646185
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| 9. |
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| 10. |
- Tuoriniemi, Jani, 1982, et al.
(författare)
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Intermethod comparison of the particle size distributions of colloidal silica nanoparticles
- 2014
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Ingår i: Science and Technology of Advanced Materials. - : Informa UK Limited. - 1468-6996 .- 1878-5514. ; 15:3
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Tidskriftsartikel (refereegranskat)abstract
- There can be a large variation in the measured diameter of nanoparticles depending on which method is used. In this work, we have strived to accurately determine the mean particle diameter of 3040 nm colloidal silica particles by using six different techniques. A quantitative agreement between the particle size distributions was obtained by scanning electron microscopy (SEM), and electrospray-scanning mobility particle sizer (ES SMPS). However, transmission electron microscopy gave a distribution shifted to smaller sizes. After confirming that the magnification calibration was consistent, this was attributed to sample preparation artifacts. The hydrodynamic diameter, d(h), was determined by dynamic light scattering (DLS) both in batch mode, and hyphenated with sedimentation field flow fractionation. Surprisingly the dh were smaller than the SEM, and ES SMPS diameters. A plausible explanation for the smaller sizes found with DLS is that a permeable gel layer forms on the particle surface. Results from nanoparticle tracking analysis were strongly biased towards larger diameters, most likely because the silica particles provide low refractive index contrast. Calculations confirmed that the sensitivity is, depending on the shape of the laser beam, strongly size dependent for particles with diameters close to the visualization limit.
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