138 research outputs found
Rapid in situ assessment of Cu-ion mediated effects and antibacterial efficacy of copper surfaces
No full textRelease of metal ions from metal-based surfaces has been considered one of the main drivers of their antimicrobial activity. Here we describe a method that enables parallel assessment of metal ion release from solid metallic surfaces and antimicrobial efficacy of these surfaces in a short time period. The protocol involves placement of a small volume of bioluminescent bacteria onto the tested surface and direct measurement of bioluminescence at various time points. In this study, two recombinant Escherichia coli strains, one expressing bioluminescence constitutively and applicable for general antimicrobial testing, and the other induced by Cu ions, were selected. Decrease in bioluminescence of constitutive E. coli on the surfaces showed a good correlation with the decrease in bacterial viability. Response of Cu-inducible E. coli showed a correlation with Cu content in the tested surfaces but not with Cu dissolution suggesting the role of direct bacteria-surface contact in Cu ion-driven antibacterial effects. In summary, the presented protocol enables the analysis of microbial toxicity and bioavailability of surface-released metal ions directly on solid surfaces within 30-60 min. Although optimized for copper and copper alloy surfaces and E. coli, the method can be extended to other types of metallic surfaces and bacterial strains
Mechanisms of toxic action of silver nanoparticles in the protozoan Tetrahymena thermophila: From gene expression to phenotypic events
No full textSilver nanoparticles (AgNPs) are highly toxic to aquatic organisms, however, there is no consensus whether the toxicity is caused solely by released Ag-ions or also by reactive oxygen species (ROS). Here, the effects of protein-coated AgNPs (14.6 nm, Collargol) were studied on viability, oxidative stress and gene expression levels in wild type strains (CU427 and CU428) of ciliate Tetrahymena thermophila. Viability-based 24 h EC50 values of AgNPs were relatively high and significantly different for the two strains: ∼100 mg/L and ∼75 mg/L for CU427 and CU428, respectively. Similarly, the expression profiles of oxidative stress (OS) related genes in the two strains were different. However, even though some OS related genes were overexpressed in AgNP-exposed ciliates, intracellular ROS level was not elevated, possibly due to efficient cellular antioxidant defence mechanisms. Compared to OS related genes, metallothionein genes were upregulated at a considerably higher level (36 versus 5000-fold) suggesting that Ag-ion mediated toxicity mechanism prevailed over OS related pathway. Also, comparison between Ag-ions released from AgNPs at EC50 concentration and the respective EC50 values of AgNO3 indicated that Ag-ions played a major role in the toxicity of AgNPs in T. thermophila. The study highlights the importance of combining physiological assays with gene expression analysis in elucidating the mechanisms of action of NPs to reveal subtle cellular responses that may not be detectable in bioassays. In addition, our data filled the gaps on the toxicity of AgNPs for environmentally relevant and abundant organisms. The parallel study of two wild type strains allowed us to draw conclusions on strain to strain variability in susceptibility to AgNPs
Development of Bacterial Biosensors and Human Stem Cell-Based In Vitro Assays for the Toxicological Profiling of Synthetic Nanoparticles. Rekombinantsetel sensorbakteritel ja inimese t\ufcvirakkudel p\uf5hinevate in vitro testide v\ue4ljat\uf6\uf6tamine s\ufcnteetiliste nanoosakeste toksikoloogiliseks uurimiseks
No full textEcotoxicological Impacts of Industrially Relevant Engineered Nanomaterials: Effects on Tetrahymena thermophila. T\uf6\uf6stuslike nanomaterjalide keskkonnatoksilisuse hindamine: nanoosakeste m\uf5ju algloomale Tetrahymena thermophila
No full textConjugation-driven horizontal gene transfer in bacteria on antimicrobial surfaces
No full textConjugation is the main mechanism of horizontal gene transfer of antibiotic resistance genes
between bacteria. There is evidence that the presence of trace amounts of antimicrobials in
the environment may increase the conjugation frequency between bacteria and thus, potential
spread of antibiotic resistance genes. However, to date the effect of stress conditions,
including the presence of antimicrobials, on conjugation is relatively modestly studied and
almost no studies are available about the effect of antimicrobial surfaces on conjugation
frequency. This study first constructed an optimized conjugation protocol for solid surfaces.
For that, a chromosomally marked strain of Pseudomonas putida KT2440 to be used as recipient
strain in conjugation, was constructed. As a donor strain, Escherichia coli CSH26
with conjugative plasmid pKJK5 was used. The optimal experimental conditions: organic
content, conjugation time, and donor-to-recipient ratio on conjugation frequency, were studied.
For the conjugation experiments, a series of copper- silver- and quaternary ammonium-
based surfaces that were expected to show an antimicrobial effect, were selected. Plastic and
stainless-steel surfaces served as controls with no expected antimicrobial activity. Prior to
conjugation, viability of donor and recipient on test surfaces was analyzed and the most toxic
surfaces were not included in conjugation assay. On selected surfaces, conjugation experiments
were carried out for 24 h and conjugation frequencies were calculated for each surface.
The results showed that the presence of low level of copper on surface may promote conjugation
while silver- and quaternary ammonium compounds-based surfaces did not significantly
affect conjugation frequency
A molecular probe for the detection of polar lipids in live cells
No full textData source: Supporting Information, http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0161557#sec017Lipids have an important role in many aspects of cell biology, including membrane architecture/compartment formation, intracellular traffic, signalling, hormone regulation, inflammation, energy storage and metabolism. Lipid biology is therefore integrally involved in major human diseases, including metabolic disorders, neurodegenerative diseases, obesity, heart disease, immune disorders and cancers, which commonly display altered lipid transport and metabolism. However, the investigation of these important cellular processes has been limited by the availability of specific tools to visualise lipids in live cells. Here we describe the potential for ReZolve-L1™ to localise to intracellular compartments containing polar lipids, such as for example sphingomyelin and phosphatidylethanolamine. In live Drosophila fat body tissue from third instar larvae, ReZolve-L1™ interacted mainly with lipid droplets, including the core region of these organelles. The presence of polar lipids in the core of these lipid droplets was confirmed by Raman mapping and while this was consistent with the distribution of ReZolve-L1™ it did not exclude that the molecular probe might be detecting other lipid species. In response to complete starvation conditions, ReZolve-L1™ was detected mainly in Atg8-GFP autophagic compartments, and showed reduced staining in the lipid droplets of fat body cells. The induction of autophagy by Tor inhibition also increased ReZolve-L1™ detection in autophagic compartments, whereas Atg9 knock down impaired autophagosome formation and altered the distribution of ReZolve-L1™. Finally, during Drosophila metamorphosis fat body tissues showed increased ReZolve-L1™ staining in autophagic compartments at two hours post puparium formation, when compared to earlier developmental time points. We concluded that ReZolve-L1™ is a new live cell imaging tool, which can be used as an imaging reagent for the detection of polar lipids in different intracellular compartments.Christie A. Bader, Tetyana Shandala, Elizabeth A. Carter, Angela Ivask, Taryn Guinan, Shane M. Hickey, Melissa V. Werrett, Phillip J. Wright, Peter V. Simpson, Stefano Stagni, Nicolas H. Voelcker, Peter A. Lay, Massimiliano Massi, Sally E. Plush, Douglas A. Brook
Mikroobide interaktsioonid tahkete eluta pindadega: metoodiline k\ue4sitlus. Microbial Interactions with Inanimate Solid Surfaces: A Methodological Approach
No full textSingle cell level quantification of nanoparticle-cell interactions using mass cytometry
No full textPublished: July 10, 2017Quantification of cell-associated nanoparticles (NPs) is a paramount question in both nanomedicine and nanotoxicology. Inductively coupled plasma mass spectrometry is a well-established method to resolve cell-associated (metal) NPs in bulk cell populations, however, such analysis at single cell level remains a challenge. Here we used mass cytometry, a technique that combines single cell analysis and time-of-flight mass spectrometry, to quantitatively analyze extra- and intracellular silver (Ag) in individual Ag NP exposed human T-lymphocytes. The results revealed significant population heterogeneity: for example, in lymphocytes exposed to 3 μg of 30 nm branched polyethylene imine coated Ag NPs/mL the extracellularly bound Ag varied from 79 to 560 fg and cellular uptake from 17 to 121 fg. Similar amplitude of heterogeneity was observed in cells exposed to various doses of Ag NPs with other sizes and surface coatings, demonstrating the importance of single cell analysis when studying NP-cell interactions. Although mass cytometry has some shortcomings such as inability to analyze potential transformation or dissolution of NPs in cells, we consider this method as the most promising for quantitative assessment of cell-NP interaction at single cell level.Angela Ivask, Andrew J. Mitchell, Christopher M. Hope, Simon C. Barry, Enzo Lombi, and Nicolas H. Voelcke
Eesti pressifotograafide kogemused traagiliste sündmuste kajastamisel
No full textVälismaailma kajastamisel fotode abil on pikk ajalugu fotosid peetakse täpseimateks meediumiteks. Seetõttu leiavad fotod ka laialdast kajastust meedias uudiste juures nii üksikute piltidena kui galeriidena. Fotod annavad reaalse pildi sündmuskohast ja sellest, mis toimus. Sealjuures kannavad pressifotograafid kahte rolli – ajakirjaniku ja fotograafi. Seetõttu saab neid pidada ka ühiskonna valvekoerteks, olles esimene filter sündmuspaiga ja toimetuse vahel – fotograaf on toimetuse silmad.
Pressifotograafid esindavad mitmeid erinevaid rolle, näiteks on nad kunstnikud, kes valgusega maalivad ja oma tõlgendust läbi foto esitlevad. Teisalt on nad toimetuse esindajad ja osa ajakirjanduspraktikast ehk justkui ajakirjanikud. Samas nähakse neid tihti kui ainult tehnilist tuge reporteritele, kes esitavad visuaalseid tõendeid. Selle kõige juures on nad ka lihtsalt inimesed, kes suures osas teevad otsuseid enda moraalse kompassi ja sisetunde järgi. Kuid pressifotograafide töös jäävad kõlama kaks põhilist rolli – fotograaf ja ajakirjanik ehk kokkuvõtvalt esimene väravavalvur sündmuse kajastamisel.
Magistritöö eesmärk oli uurida Eesti pressifotograafide kogemusi traagiliste sündmuste kajastamisel – milline on tööprotsess, millised on kaalutluskohad ja kuidas mõjutab edasi- ja tagasiside pressifotograafide tööd. Selle uurimiseks viisin läbi poolstruktureeritud intervjuud viie Eesti pressifotograafiga erinevatest väljaannetest.
Tööst ilmnes, et fototoimetusi ei võeta võrdväärse partneriga. Samuti järeldus, et üheste reeglite puudumine traagiliste sündmuste kajastamisel mõjutab eelkõige pressifotograafide ja ajakirjanike tööd. Samas mõjutab see ka auditooriumit. Traagiliste sündmuste kajastamise olulisus on ideaalses maailmas ohutuse meelde tuletamine, kuid reaalsus näitab, et seda tehakse suuresti reklaamirahade tõttu. Peamised kaalutluskohad tulenevad pressifotograafi rolli identifitseerimises, vastutuse võtmises ja eetilisuses ehk kuidas ja milliseid pilte traagilistest sündmustest edasi anda. Pigem tahetakse võtta oma piltide eest vastutus ja nähakse seda nii, et vastutus juba on fotograafil sellest hetkest kui ta pilti teeb ja fotod toimetusele edastab.
Mis puutub edasi- ja tagasisidesse, siis uuringust selgus, et edasisidet ei peetud nii oluliseks kui tagasisidet. Tagasiside puhul taheti kirjeldavat tagasisidet, millest oleks fotograafidel kasu. Lisaks üheste reeglite puudumisele puudub ka toimetuse tugi traagiliste sündmuste, eriti lähetuste kajastamisel. Uuringust selgus, et Eestis puudub koolides pressifotograafiat käsitlev õpe, mis annaks tulevastele pressifotograafidele hea põhja alla. Lisaks peeti oluliseks õpetada pressifotograafidele fototoimetamise oskust, mis aitaks fotograafidel paremini piltide seas esmase valiku teha.https://www.ester.ee/record=b5450981*es
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