umu.sePublications
Change search
Refine search result
1 - 21 of 21
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1. Andrii, Dudnyk
    et al.
    Matthew, Burman
    Ludmyla, Kulyk
    Olena, Rzhepishevska
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    M/XDR‐TB treatment perspective: how to avoid mountains of pills via digital technologies2018In: Respirology (Carlton South. Print), ISSN 1323-7799, E-ISSN 1440-1843, Vol. 23, no 6, p. 636-637Article in journal (Refereed)
  • 2. Burman, Matthew
    et al.
    Nikolayenskyy, Vladyslav
    Kontsevaya, Irina
    Molina-Moya, Barbara
    Rzhepishevska, Olena
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Guglielmetti, Lorenzo
    Tackling the MDR-TB epidemic in Ukraine: every little helps … and much more needed2018In: Journal of Public Health, ISSN 2198-1833, E-ISSN 1613-2238, Vol. 40, no 1, p. 210-211Article in journal (Refereed)
  • 3. Chung, Jade C. S.
    et al.
    Rzhepishevska, Olena
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Welch, Martin
    Type III secretion system expression in oxygen-limited Pseudomonas aeruginosa cultures is stimulated by isocitrate lyase activity2013In: Open Biology, ISSN 2046-2441, E-ISSN 2046-2441, Vol. 3, article id 120131Article in journal (Refereed)
    Abstract [en]

    Pseudomonas aeruginosa is an opportunistic human pathogen and a common cause of chronic infections in individuals with cystic fibrosis (CF). Oxygen limitation was recently reported to regulate the expression of a major virulence determinant in P. aeruginosa, the type III secretion system (T3SS). Here, we show that expression of the T3SS in oxygen-limited growth conditions is strongly dependent on the glyoxylate shunt enzyme, isocitrate lyase (ICL; encoded by aceA), which was previously shown to be highly expressed in CF isolates. ICL-dependent regulation of the T3SS did not alter the expression level of the master transcriptional regulator, ExsA, but did affect expression of the T3 structural proteins, effectors and regulators (ExsC, ExsD and ExsE). An aceA mutant displayed enhanced biofilm formation during anaerobic growth, which suggested that AceA-dependent modulation of type III secretion might impinge upon the RetS/LadS signalling pathways. Indeed, our data suggest that RetS is able to mediate some of its effects through AceA, as expression of aceA in trans partially restored T3SS expression in a retS mutant. Our findings indicate that AceA is a key player in the metabolic regulation of T3SS expression during oxygen-limited growth of P. aeruginosa. To the best of our knowledge, this is the first demonstration that the T3SS can be regulated by factors that do not affect ExsA expression levels.

  • 4.
    Dopson, Mark
    et al.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Kupka, Daniel
    Halinen, Anna-Kaisa
    Rahunen, Nelli
    Özkaya, Bestamin
    Sahinkaya, Erkan
    Rzhepishevska, Olena I
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Kaksonen, Anna H
    Karnachuk, Olia V
    Tuovinen, IH
    Puhakka, Jaakko A
    Iron oxidation and bioleaching potential at low temperatures2007In: Biohydrometallurgy: from the single cell to the environment / [ed] Axel Schippers, Zurich: Trans Tech Publications Inc., 2007, p. 578-578Conference paper (Refereed)
  • 5. Dudnyk, Andrii
    et al.
    Rzhepishevska, Olena
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Rogach, Kostiantyn
    Kutsyna, Galyna
    Lange, Christoph
    Multidrug-resistant tuberculosis in Ukraine at a time of military conflict2015In: The International Journal of Tuberculosis and Lung Disease, ISSN 1027-3719, E-ISSN 1815-7920, Vol. 19, no 4, p. 492-493Article in journal (Refereed)
  • 6. Ferreira, Magda
    et al.
    Rzhepishevska, Olena
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Grenho, Liliana
    Malheiros, Danila
    Gonçalves, Lídia
    Almeida, António J.
    Jordão, Luisa
    Ribeiro, Isabel A.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Gomes, Pedro
    Bettencourt, Ana
    Levofloxacin-loaded bone cement delivery system: highly effective against intracellular bacteria and Staphylococcus aureus biofilms2017In: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 532, no 1, p. 241-248Article in journal (Refereed)
    Abstract [en]

    Staphylococcus aureus is a major pathogen in bone associated infections due to its ability to adhere and form biofilms on bone and/or implants. Moreover, recrudescent and chronic infections have been associated with S. aureus capacity to invade and persist within osteoblast cells. With the growing need of novel therapeutic tools, this research aimed to evaluate some important key biological properties of a novel carrier system composed of acrylic bone cement (polymethylmethacrylate – PMMA), loaded with a release modulator (lactose) and an antibiotic (levofloxacin).

    Levofloxacin-loaded bone cement (BC) exhibited antimicrobial effects against planktonic and biofilm forms of S. aureus (evaluated by a flow chamber system). Moreover, novel BC formulation showed high anti-bacterial intraosteoblast activity. This fact led to the conclusion that levofloxacin released from BC matrices could penetrate the cell membrane of osteoblasts and be active against S. aureus strains in the intracellular environment. Furthermore, levofloxacin-BC formulations showed no significant in vitro cytotoxicity and no allergic potential (measured by the in vivo chorioallantoic membrane assay). Our results indicate that levofloxacin-loaded BC has potential as a local antibiotic delivery system for treating S. aureus associated bone infections.

  • 7. Gross, Jeremy
    et al.
    Passmore, Ian J
    Chung, Jade Cs
    Rzhepishevska, Olena
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Welch, Martin
    Universal soldier: Pseudomonas aeruginosa - an opportunistic generalist2013In: Frontiers in Biology, ISSN 1674-7984, Vol. 8, no 4, p. 387-394Article in journal (Refereed)
    Abstract [en]

    The opportunistic pathogen Pseudomonas aeruginosa commonly causes chronic and ultimately deadly lung infections in individuals with the genetic disease cystic fibrosis (CF). P. aeruginosa is metabolically diverse; it displays a remarkable ability to adapt to and successfully occupy almost any niche, including the ecologically complex CF lung. These P. aeruginosa lung infections are a fascinating example of microbial evolution within a "natural" ecosystem. Initially, P. aeruginosa shares the lung niche with a plethora of other microorganisms and is vulnerable to antibiotic challenges. Over time, adaptive evolution leads to certain commonly-observed phenotypic changes within the P. aeruginosa population, some of which render it resistant to antibiotics and apparently help it to out-compete the other species that co-habit the airways. Improving genomics techniques continue to elucidate the evolutionary mechanisms of P. aeruginosa within the CF lung and will hopefully identify new vulnerabilities in this robust and versatile pathogen. © 2013 Higher Education Press and Springer-Verlag Berlin Heidelberg.

  • 8.
    Hakobyan, Shoghik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Rzhepishevska, Olena
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Barbero, David R.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Functionalization of zwitterionic polymer brushes, do they remain antifouling?2018In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 50, no 11, p. 1001-1006Article in journal (Refereed)
    Abstract [en]

    Polymer brushes are surface coatings that can be tailored in many ways to suit specific demands including reduction of protein and bacterial fouling of biomaterials. Previously, we reported that antifouling poly (2-(methacryloxy)ethyl)dimethyl-3-sulphopropyl ammonium hydroxide) brushes dramatically reduced formation of bacterial biofilm. We hypothesized that: (1) this brush could be efficiently functionalized with a small molecule (2-oxo-2-[N-(2,4,6-trihydroxybenzylidene)-hydrazino]-acetamide, ME0163, hydrazone) and that (2) the antifouling property would remain also after functionalization. Diblock co-polymer brushes of 2-(methacryloxy)ethyl)dimethyl-3-sulphopropyl ammonium hydroxide and poly (glycidyl methacrylate) were formed by surface-initiated atom transfer radical polymerization (SI-ATRP), and the ME0163 hydrazone was covalently bound to the surface via a ring-opening reaction. Functionalization of the surfaces was followed by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and UV-Vis spectroscopy. The influence of temperature, reaction time, and reagent concentrations on the immobilization process was investigated. Surfaces with high degree of functionalization could be made in this way. However, the functionalization rendered the surface more hydrophobic, and the antifouling property of the brush was lost, thus, disproving the second of our starting hypotheses but corroborating the first.

  • 9.
    Hakobyan, Shoghik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Rzhepishevska, Olena
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Björn, Erik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Boily, Jean-François
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Influence of Chelation Strength and Bacterial Uptake of Gallium Salicylidene Acylhydrazide on Biofilm Formation and Virulence by Pseudomonas aeruginosa2016In: Journal of Inorganic Biochemistry, ISSN 0162-0134, E-ISSN 1873-3344, Vol. 160, p. 24-32Article in journal (Refereed)
    Abstract [en]

    Development of antibiotic resistance in bacteria causes major challenges for our society and has prompted a great need for new and alternative treatment methods for infection. One promising approach is to target bacterial virulence using for example salicylidene acylhydrazides (hydrazones). Hydrazones coordinate metal ions such as Fe(III) and Ga(III) through a five-membered and a six-membered chelation ring. One suggested mode of action is via restricting bacterial Fe uptake. Thus, it was hypothesized that the chelating strength of these substances could be used to predict their biological activity on bacterial cells. This was investigated by comparing Ga chelation strength of two hydrazone complexes, as well as bacterial Ga uptake, biofilm formation, and virulence in the form of production and secretion of a toxin (ExoS) by Pseudomonas aeruginosa. Equilibrium constants for deprotonation and Ga(III) binding of the hydrazone N′-(5-chloro-2-hydroxy-3-methylbenzylidene)-2,4-dihydroxybenzhydrazide (ME0329), with anti-virulence effect against P. aeruginosa, were determined and compared to bacterial siderophores and the previously described Ga(III) 2-oxo-2-[N-(2,4,6-trihydroxy-benzylidene)-hydrazino]-acetamide (Ga-ME0163) and Ga-citrate complexes. In comparison with these two complexes, it was shown that the uptake of Ga(III) was higher from the Ga-ME0329 complex. The results further show that the Ga-ME0329 complex reduced ExoS expression and secretion to a higher extent than Ga-citrate, Ga-ME0163 or the non-coordinated hydrazone. However, the effect against biofilm formation by P. aeruginosa, by the ME0329 complex, was similar to Ga-citrate and lower than what has been reported for Ga-ME0163.

  • 10.
    Kupka, Daniel
    et al.
    Institute of Geotechnics, Slovak Academy of Sciences, Watsonova 45, SK-043 53 Koice, Slovakia.
    Rzhepishevska, Olena
    Umeå University, Faculty of Science and Technology, Molecular Biology (Faculty of Science and Technology).
    Dopson, Mark
    Umeå University, Faculty of Science and Technology, Molecular Biology (Faculty of Science and Technology).
    Lindström, Börje
    Umeå University, Faculty of Science and Technology, Molecular Biology (Faculty of Science and Technology).
    Karnachuk, Olia V
    3Department of Agriculture and Environmental Science, Tomsk State University, Prospekt Lenina 36, 634050 Tomsk, Russia.
    Tuovinen, Olli H
    Department of Microbiology, Ohio State University, 484 West 12th Avenue, Columbus, Ohio 43210.
    Bacterial oxidation of ferrous iron at low temperatures.2007In: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 97, no 6, p. 1470-1478Article in journal (Refereed)
    Abstract [en]

    This study comprises the first report of ferrous iron oxidation by psychrotolerant, acidophilic iron-oxidizing bacteria capable of growing at 5 degrees C. Samples of mine drainage-impacted surface soils and sediments from the Norilsk mining region (Taimyr, Siberia) and Kristineberg (Skellefte district, Sweden) were inoculated into acidic ferrous sulfate media and incubated at 5 degrees C. Iron oxidation was preceded by an approximately 3-month lag period that was reduced in subsequent cultures. Three enrichment cultures were chosen for further work and one culture designated as isolate SS3 was purified by colony isolation from a Norilsk enrichment culture for determining the kinetics of iron oxidation. The 16S rRNA based phylogeny of SS3 and two other psychrotolerant cultures, SS5 from Norilsk and SK5 from Northern Sweden, was determined. Comparative analysis of amplified 16S rRNA gene sequences showed that the psychrotolerant cultures aligned within Acidithiobacillus ferrooxidans. The rate constant of iron oxidation by growing cultures of SS3 was in the range of 0.0162-0.0104 h(-1) depending on the initial pH. The oxidation kinetics followed an exponential pattern, consistent with a first order rate expression. Parallel iron oxidation by a mesophilic reference culture of Acidithiobacillus ferrooxidans was extremely slow and linear. Precipitates harvested from the 5 degrees C culture were identified by X-ray diffraction as mixtures of schwertmannite (ideal formula Fe(8)O(8)(OH)(6)SO(4)) and jarosite (KFe(3)(SO(4))(2)(OH)(6)). Jarosite was much more dominant in precipitates produced at 30 degrees C. (c) 2007 Wiley Periodicals, Inc.

  • 11.
    Liljeqvist, Maria
    et al.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Rzhepishevska, Olena I
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Dopson, Mark
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Gene Identification and Substrate Regulation Provide Insights into Sulfur Accumulation during Bioleaching with the Psychrotolerant Acidophile Acidithiobacillus ferrivorans2013In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 79, no 3, p. 951-957Article in journal (Refereed)
    Abstract [en]

    The psychrotolerant acidophile Acidithiobacillus ferrivorans has been identified from cold environments and has been shown to use ferrous iron and inorganic sulfur compounds as its energy sources. A bioinformatic evaluation presented in this study suggested that Acidithiobacillus ferrivorans utilized a ferrous iron oxidation pathway similar to that of the related species Acidithiobacillus ferrooxidans. However, the inorganic sulfur oxidation pathway was less clear, since the Acidithiobacillus ferrivorans genome contained genes from both Acidithiobacillus ferrooxidans and Acidithiobacillus caldus encoding enzymes whose assigned functions are redundant. Transcriptional analysis revealed that the petA1 and petB1 genes (implicated in ferrous iron oxidation) were downregulated upon growth on the inorganic sulfur compound tetrathionate but were on average 10.5-fold upregulated in the presence of ferrous iron. In contrast, expression of cyoB1 (involved in inorganic sulfur compound oxidation) was decreased 6.6-fold upon growth on ferrous iron alone. Competition assays between ferrous iron and tetrathionate with Acidithiobacillus ferrivorans SS3 precultured on chalcopyrite mineral showed a preference for ferrous iron oxidation over tetrathionate oxidation. Also, pure and mixed cultures of psychrotolerant acidophiles were utilized for the bioleaching of metal sulfide minerals in stirred tank reactors at 5 and 25°C in order to investigate the fate of ferrous iron and inorganic sulfur compounds. Solid sulfur accumulated in bioleaching cultures growing on a chalcopyrite concentrate. Sulfur accumulation halted mineral solubilization, but sulfur was oxidized after metal release had ceased. The data indicated that ferrous iron was preferentially oxidized during growth on chalcopyrite, a finding with important implications for biomining in cold environments.

  • 12.
    Näsström, Elin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Parry, Christopher M.
    Thieu, Nga Tran Vu
    Maude, Rapeephan R.
    de Jong, Hanna K.
    Fukushima, Masako
    Rzhepishevska, Olena
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Marks, Florian
    Panzner, Ursula
    Im, Justin
    Jeon, Hyonjin
    Park, Seeun
    Chaudhury, Zabeen
    Ghose, Aniruddha
    Samad, Rasheda
    Van, Tan Trinh
    Johansson, Anders
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Dondorp, Arjen M.
    Thwaites, Guy E.
    Faiz, Abul
    Antti, Henrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Baker, Stephen
    Reproducible diagnostic metabolites in plasma from typhoid fever patients in Asia and Africa2017In: eLIFE, E-ISSN 2050-084X, Vol. 6, article id e15651Article in journal (Refereed)
    Abstract [en]

    Salmonella Typhi is the causative agent of typhoid. Typhoid is diagnosed by blood culture, a method that lacks sensitivity, portability and speed. We have previously shown that specific metabolomic profiles can be detected in the blood of typhoid patients from Nepal (Nasstrom et al., 2014). Here, we performed mass spectrometry on plasma from Bangladeshi and Senegalese patients with culture confirmed typhoid fever, clinically suspected typhoid, and other febrile diseases including malaria. After applying supervised pattern recognition modelling, we could significantly distinguish metabolite profiles in plasma from the culture confirmed typhoid patients. After comparing the direction of change and degree of multivariate significance, we identified 24 metabolites that were consistently up- or down regulated in a further Bangladeshi/Senegalese validation cohort, and the Nepali cohort from our previous work. We have identified and validated a metabolite panel that can distinguish typhoid from other febrile diseases, providing a new approach for typhoid diagnostics.

  • 13.
    Ruhal, Rohit
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Antti, Henrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Rzhepishevska, Olena
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Boulanger, Nicolas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Barbero, David R.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wai, Sun Nyunt
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Uhlin, Bernt Eric
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    A multivariate approach to correlate bacterial surface properties to biofilm formation by lipopolysaccharide mutants of Pseudomonas aeruginosa2015In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 127, no 0, p. 182-191Article in journal (Refereed)
    Abstract [en]

    Abstract Bacterial biofilms are involved in various medical infections and for this reason it is of great importance to better understand the process of biofilm formation in order to eradicate or mitigate it. It is a very complex process and a large range of variables have been suggested to influence biofilm formation. However, their internal importance is still not well understood. In the present study, a range of surface properties of Pseudomonas aeruginosa lipopolysaccharide mutants were studied in relation to biofilm formation measured in different kinds of multi-well plates and growth conditions in order to better understand the complexity of biofilm formation. Multivariate analysis was used to simultaneously evaluate the role of a range of physiochemical parameters under different conditions. Our results suggest the presence of serum inhibited biofilm formation due to changes in twitching motility. From the multivariate analysis it was observed that the most important parameters, positively correlated to biofilm formation on two types of plates, were high hydrophobicity, near neutral zeta potential and motility. Negative correlation was observed with cell aggregation, as well as formation of outer membrane vesicles and exopolysaccharides. This work shows that the complexity of biofilm formation can be better understood using a multivariate approach that can interpret and rank the importance of different factors being present simultaneously under several different environmental conditions, enabling a better understanding of this complex process.

  • 14.
    Rzhepishevska, Olena
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ekstrand-Hammarström, Barbro
    Swedish Defence Research Institute (FOI), Umeå, Sweden .
    Popp, Maximilian
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Björn, Erik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Bucht, Anders
    Swedish Defence Research Institute (FOI), Umeå, Sweden .
    Sjöstedt, Anders
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Antti, Henrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    The antibacterial activity of Ga3+ is influenced by Llgand complexation as well as the bacterial carbon source2011In: Antimicrobial Agents and Chemotherapy, ISSN 0066-4804, E-ISSN 1098-6596, Vol. 55, no 12, p. 5568-5580Article in journal (Refereed)
    Abstract [en]

    Gallium ions have previously been shown to exhibit antibacterial and antibiofilm properties. In this study we report differential bactericidal activity of two gallium complexes; gallium desferrioxamine B (Ga-DFOB) and gallium citrate (Ga-cit). Modeling of gallium speciation in growth medium showed that DFOB and citrate both can prevent precipitation of Ga(OH)(3), but some precipitation can occur above pH 7 with citrate. Despite this, Ga-cit inhibitory concentrations (IC(90)) were lower than those of Ga-DFOB for clinical isolates of Pseudomonas aeruginosa, and several reference strains of other bacterial species. Treatment with Ga compounds mitigated damage inflicted on murine J774 macrophage-like cells infected with P. aeruginosa PAO1. Again, Ga-cit showed more potent mitigation than did Ga-DFOB. Ga was also taken up more efficiently by P. aeruginosa in the form of Ga-cit than in the form of Ga-DFOB. Neither Ga-cit nor Ga-DFOB was toxic to several human cell lines tested and no pro-inflammatory activity was detected in human lung epithelial cells after exposure in vitro. Metabolomic analysis was used to delineate the effects of Ga-cit on the bacterial cell. Exposure to Ga resulted in lower concentrations of glutamate, a key metabolite for P. aeruginosa, and of many amino acids, indicating that Ga affects various biosynthesis pathways. Altered protein expression profile in presence of Ga-cit suggested that some compensatory mechanisms were activated in the bacterium. Furthermore, the antibacterial effect of Ga was shown to vary depending on the carbon source, which has importance in the context of medical applications of gallium.

  • 15.
    Rzhepishevska, Olena
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hakobyan, Shoghik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ekstrand-Hammarström, Barbro
    Swedish Defense Research Institute (FOI), Umeå, Sweden.
    Nygren, Yvonne
    Swedish Defense Research Institute (FOI), Umeå, Sweden.
    Karlsson, Torbjörn
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Bucht, Anders
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Pulmonary Medicine. Swedish Defense Research Institute (FOI), Umeå, Sweden.
    Elofsson, Mikael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Boily, Jean-François
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    The gallium(III)-salicylidene acylhydrazide complex shows synergistic anti-biofilm effect and inhibits toxin production by Pseudomonas aeruginosa2014In: Journal of Inorganic Biochemistry, ISSN 0162-0134, E-ISSN 1873-3344, Vol. 138, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Bacterial biofilms cause a range of problems in many areas and especially in health care. Biofilms are difficult to eradicate with traditional antibiotics and consequently there is a need for alternative ways to prevent and/or remove bacterial biofilms. Furthermore, the emergence of antibiotic resistance in bacteria creates a challenge to find new types of antibiotics with a lower evolutionary pressure for resistance development. One route to develop such drugs is to target the so called virulence factors, i.e. bacterial systems used when bacteria infect a host cell. This study investigates synergy effects between Ga(III) ions, previously reported to suppress biofilm formation and growth in bacteria, and salicylidene acylhydrazides (hydrazones) that have been proposed as antivirulence drugs targeting the type three secretion system used by several Gram-negative pathogens, including Pseudomonas aerugionosa, during bacterial infection of host cells. A library of hydrazones was screened for: Fe(III) binding, enhanced anti-biofilm effect with Ga(III) on P. aeruginosa, and low cytotoxicity to mammalian cells. The metal coordination for the most promising ligand, 2-Oxo-2-[N-(2,4,6-trihydroxy-benzylidene)-hydrazino]-acetamide (ME0163) with Ga(III) was investigated using extended X-ray absorption fine structure spectroscopy as well as density functional theory. The results showed that Ga(III) chelates the hydrazone with 5- and 6-membered chelating rings, and that the Ga(III)-ME0163 complex enhanced the antibiofilm effect of Ga(III) while suppressing the type three secretion system in P. aeruginosa. The latter effect was not observed for the hydrazone alone and was similar for Ga(III)-citrate and Ga(III)-ME0163 complexes, indicating that the inhibition of virulence was caused by Ga(III).

  • 16.
    Rzhepishevska, Olena
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hakobyan, Shoghik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ruhal, Rohit
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Gautrot, Julien
    Barbero, David
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    The surface charge of anti-bacterial coatings alters motility and biofilm architecture2013In: Journal of Biomaterials Science. Polymer Edition, ISSN 0920-5063, E-ISSN 1568-5624, Vol. 1, no 6, p. 589-602Article in journal (Refereed)
    Abstract [en]

    Bacterial biofilms affect many areas of human activity including food processing, transportation, public infrastructure, and most importantly healthcare. This study addresses the prevention of biofilms and shows that the surface charge of an abiotic substrate influences bacterial motility as well as the morphology and physiology of the biofilm. Grafting-from polymerisation was used to create polymer brush surfaces with different characteristics, and the development of Pseudomonas aeruginosa biofilms was followed using confocal microscopy. Interestingly, two types of biofilms developed on these surfaces: mushroom structures with high levels of cyclic diguanylate (c-di-GMP) were found on negatively charged poly (3-sulphopropylmethacrylate) (SPM) and zwitterionic poly (2-(methacryloyloxy)ethyl)dimethyl-3-sulphoproyl) ammonium hydroxide) (MEDSAH), while flat biofilms developed on glass, positively charged poly (2-(methacryloyloxy)-ethyl trimethyl ammonium chloride) (METAC), protein-repellent poly oligo(ethylene glycol methyl ether methacrylate) (POEGMA) and hydrophobic polymethylmethacrylate (PMMA). The results show that of all the surfaces studied, overall the negatively charged polymer brushes were most efficient in reducing bacterial adhesion and biofilm formation. However, the increased level of regulatory c-di-GMP in mushroom structures suggests that bacteria are capable of a quick physiological response when exposed to surfaces with varying physicochemical characteristics enabling some bacterial colonization also on negatively charged surfaces.

  • 17.
    Rzhepishevska, Olena I.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Dopson, Mark
    Sulphur Accumulation During Low Temperature BioleachingManuscript (preprint) (Other (popular science, discussion, etc.))
  • 18.
    Rzhepishevska, Olena I.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Limanska, Nataliia
    Galkin, Mykola
    Lacoma, Alicia
    Lundquist, Margaretha
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sokol, Dmytro
    Hakobyan, Shoghik
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Queen Mary University of London, London, UK.
    Sjöstedt, Anders
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Prat, Cristina
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Characterization of clinically relevant model bacterial strains of Pseudomonas aeruginosa for anti-biofilm testing of materials2018In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 76, p. 99-107Article in journal (Refereed)
    Abstract [en]

    There is a great interest in developing novel anti-biofilm materials in order to decrease medical device-associated bacterial infections causing morbidity and high healthcare costs. However, the testing of novel materials is often done using bacterial lab strains that may not exhibit the same phenotype as clinically relevant strains infecting medical devices. Furthermore, no consensus of strain selection exists in the field, making results very difficult to compare between studies. In this work, 19 clinical isolates of Pseudomonas aeruginosa originating from intubated patients in an intensive care unit have been characterized and compared to the lab reference strain PAO1 and a rmlC lipopolysaccharide mutant of PAO1. The adhesion and biofilm formation was monitored, as well as cell properties such as hydrophobicity, zeta potential and motility. Two groups of isolates were observed: one with high adhesion to polymer surfaces and one with low adhesion (the latter including PAO1). Furthermore, detailed biofilm assays in a flow system were performed using five characteristic isolates from the two groups. Confocal microscopy showed that the adhesion and biofilm formation of four of these five strains could be reduced dramatically on zwitterionic surface coatings. However, one isolate with pronounced swarming colonized and formed biofilm also on the antifouling surface. We demonstrate that the biofilm properties of clinical isolates can differ greatly from that of a standard lab strain and propose two clinical model strains for testing of materials designed for prevention of biofilm formation in the respiratory tract. The methodology used could beneficially be applied for screening of other collections of pathogens to identify suitable model strains for in vitro biofilm testing.

    Statement of Significance: Medical-device associated infections present a great challenge in health care. Therefore, much research is undertaken to prevent bacterial colonization of new types of biomaterials. The work described here characterizes, tests and presents a number of clinically relevant bacterial model strains for assessing biofilm formation by Pseudomonas aeruginosa. Such model strains are of importance as they may provide better predictability of lab testing protocols with respect to how well materials would perform in an infection situation in a patient. Furthermore, this study uses the strains to test the performance of polymer surfaces designed to repel bacterial adhesion and it is shown that the biofilm formation for four out of the five tested bacterial strains was reduced.

    The full text will be freely available from 2020-06-12 00:00
  • 19.
    Rzhepishevska, Olena I
    et al.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Valdés, Jorge
    Center for Bioinformatics and Genome Biology, Life Science Foundation, MIFAB and Andrés Bello University, Santiago, Chile.
    Marcinkeviciene, Liucija
    Department of Molecular Microbiology and Biotechnology, Institute of Biochemistry, Mokslininku 12, Vilnius LT-08662, Lithuania.
    Gallardo, Camelia Algora
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Meskys, Rolandas
    Department of Molecular Microbiology and Biotechnology, Institute of Biochemistry, Mokslininku 12, Vilnius LT-08662, Lithuania.
    Bonnefoy, Violaine
    CNRS, IBSM, Laboratoire de Chimie Bactérienne, 31 Chemin J. Aiguier, 13402 Marseille Cedex 20, France.
    Holmes, David S.
    Center for Bioinformatics and Genome Biology, Life Science Foundation, MIFAB and Andrés Bello University, Santiago, Chile.
    Dopson, Mark
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Regulation of a novel Acidithiobacillus caldus gene cluster involved in metabolism of reduced inorganic sulfur compounds2007In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 73, no 22, p. 7367-7372Article in journal (Refereed)
    Abstract [en]

    Acidithiobacillus caldus has been proposed to play a role in the oxidation of reduced inorganic sulfur compounds (RISCs) produced in industrial biomining of sulfidic minerals. Here, we describe the regulation of a new cluster containing the gene encoding tetrathionate hydrolase (tetH), a key enzyme in the RISC metabolism of this bacterium. The cluster contains five cotranscribed genes, ISac1, rsrR, rsrS, tetH, and doxD, coding for a transposase, a two-component response regulator (RsrR and RsrS), tetrathionate hydrolase, and DoxD, respectively. As shown by quantitative PCR, rsrR, tetH, and doxD are upregulated to different degrees in the presence of tetrathionate. Western blot analysis also indicates upregulation of TetH in the presence of tetrathionate, thiosulfate, and pyrite. The tetH cluster is predicted to have two promoters, both of which are functional in Escherichia coli and one of which was mapped by primer extension. A pyrrolo-quinoline quinone binding domain in TetH was predicted by bioinformatic analysis, and the presence of an o-quinone moiety was experimentally verified, suggesting a mechanism for tetrathionate oxidation.

  • 20.
    Rzhepishevska, Olena
    et al.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Lindström, Börje
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Tuovinen, Olli H
    Department of Microbiology, Ohio State University, 484 W 12th Avenue, Columbus, Ohio 43210.
    Dopson, Mark
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Bioleaching of sulfidic tailing samples with a novel, vacuum-positive pressure driven bioreactor.2005In: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 92, no 5, p. 559-67Article in journal (Refereed)
    Abstract [en]

    This study presents a design for a novel bioreactor that uses alternating vacuum and positive pressure cycles to transfer acidic leach solution in and out of contact with finely ground sulfidic mine tailings. These tailings constitute an environmental problem that needs experimental data to support the development of management and control strategies. A conventional stirred tank bioreactor was used as a reference system. Both bioreactors were inoculated with mixed cultures of acidophilic iron and sulfur oxidizers. The rate of the bioleaching of tailings was 0.50 +/- 0.14 g Fe/L . day in the stirred tank bioreactor and 0.17 +/- 0.05 g Fe/L . day in the novel bioreactor. Microbial populations were identified in the two-bioreactor systems by analysis of 16S rRNA genes involving amplification, denaturing gradient gel electrophoresis (DGGE), cloning, and sequencing. The inoculum contained sulfur-oxidizing Acidithiobacillus caldus and Acidithiobacillus thiooxidans, iron oxidizers from the genera Leptospirillum and Ferroplasma, and a chemoorganotrophic Alicyclobacillus sp. During bioleaching of the tailings, the microbial populations in both bioreactors were similar to the inoculum culture, except that At. thiooxidans outgrew At. caldus. Sequences consistent with a Sulfobacillus sp. were amplified from both bioreactor samples although this bacterium was initially below the level of detection in the inoculum. After prolonged operation, Ferroplasma acidiphilum and an uncultured bacterium related to the CFB group were also detected in the novel bioreactor, whereas Sulfobacillus sp. was no longer detected. The novel bioreactor has potential uses in other areas of environmental biotechnology that involves periodic contact of liquids with solid substrates. (c) 2005 Wiley Periodicals, Inc.

  • 21. Trentin, Danielle S
    et al.
    Silva, Denise B
    Frasson, Amanda P
    Rzhepishevska, Olena
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    da Silva, Márcia V
    Pulcini, Elinor de L
    James, Garth
    Soares, Gabriel V
    Tasca, Tiana
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Giordani, Raquel B
    Lopes, Norberto P
    Macedo, Alexandre J
    Natural green coating inhibits adhesion of clinically important bacteria2015In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, p. 8287-Article in journal (Refereed)
    Abstract [en]

    Despite many advances, biomaterial-associated infections continue to be a major clinical problem. In order to minimize bacterial adhesion, material surface modifications are currently being investigated and natural products possess large potential for the design of innovative surface coatings. We report the bioguided phytochemical investigation of Pityrocarpa moniliformis and the characterization of tannins by mass spectrometry. It was demonstrated that B-type linked proanthocyanidins-coated surfaces, here termed Green coatings, reduced Gram-positive bacterial adhesion and supported mammalian cell spreading. The proposed mechanism of bacterial attachment inhibition is based on electrostatic repulsion, high hydrophilicity and the steric hindrance provided by the coating that blocks bacterium-substratum interactions. This work shows the applicability of a prototype Green-coated surface that aims to promote necessary mammalian tissue compatibility, while reducing bacterial colonization.

1 - 21 of 21
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf