Browsing by Subject "bakteriofaagi"
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(University of HelsinkiHelsingin yliopistoHelsingfors universitet, 2005)Clostridium botulinum on anaerobinen, gram-positiivinen, itiöivä sauvabakteeri, jota esiintyy maailmanlaajuisesti maaperässä, meressä ja meren sedimenteissä. Se tuottaa maailman voimakkainta myrkkyä, botulinumneurotoksiinia (BoNT), joka aiheuttaa botulismina tunnetun velttohalvauksen estämällä asetyylikoliini -välittäjäaineen vapautumisen hermolihasliitoksen synapsiraossa. BoNT on n.150 kDa:n pituinen polypeptidiketju, joka koostuu disulfidisillalla yhdistetystä raskas- ja kevytketjusta. C. botulinum jaetaan kuuteen serotyyppiin A-F, joista C ja D aiheuttavat botulismia vain eläimillä. Linnut, turkiseläimet ja hevoset ovat herkimpiä C-tyypin toksiinille ja naudat ja pikkumärehtijät D-tyypille. Tyypit voidaan jakaa mikrobiologisten ominaisuuksiensa mukaan myös kolmeen ryhmään I-III. C- ja D- tyyppi muodostavat III-ryhmän, jolle on ominaista, että sen toksiinintuottogeeni sijaitsee bakteriofaagissa, toisin kuin muilla ryhmillä, joilla geeni kuuluu bakteerin kromosomiin. Bakteriofaagit ovat bakteerien loisviruksia, joita löytyy kaikkialta ympäristöstämme. Niillä on säännöllinen, usein kuusikulmainen pää ja tupellinen häntä. C- ja D-tyypin faagit sisältävät kaksijuonteista DNA:ta, jossa myös BoNT-geeni sijaitsee. Infektoidessaan bakteerin faagi siirtää DNA:nsa häntää pitkin bakteerin solulimaan. C- ja D-tyypin faagin suhde isäntäsoluunsa on pseudolysogeeninen, mikä tarkoittaa sitä, että faagi pystyy vaihdellen integroitumaan ja irrottautumaan bakteerin kromosomista. Integroiduttuaan kromosomiin faagi-DNA on lysogeenisessa syklissä eli se toimii osana isäntäsolun kromosomia ja periytyy sen mukana solun jälkeläisille. Irrottautuessaan kromosomista faagi-DNA joutuu solulimassa lyyttiseen sykliin, jossa se solun toimintaan puuttumatta monistaa itseään ja rakentaa päitä ja häntiä käyttöönsä. Lopulta uudet faagit rikkovat solun purkautuessaan siitä ulos. C- ja D-tyypit ovat toksigeenisiä ainoastaan infektoiduttuaan faagilla ja menettävät toksiinintuottokykynsä, jos faagi-DNA irrottautuu kromosomista. Faagityypistä riippuu, tuottaako solu C1- vai D-tyypin toksiinia. Kaikki faagit eivät kuitenkaan pysty infektoimaan kaikkia C- ja D-tyypin kantoja antigeenisista ja morfologisista eroista johtuen. Faagin menetykseen johtavia seikkoja ei tarkalleen tiedetä, mutta kasvulle epäedulliset ympäristöolot ja sarjasiirrostukset vähentävät kantojen toksigeenisyyttä. UV-säteilyllä ja erilaisilla kemiallisilla käsittelyillä faagit saadaan irtoamaan keinotekoisesti. Neurotoksiinit syntetisoidaan ei-toksisten proteiinien kanssa osana suurempia, erikokoisia toksiinikomplekseja. Proteiinit osallistuvat BoNT:n suojaamiseen ja kiinnittymiseen. Kompleksin rakentamisesta vastaa kuusi geeniä, joita koodataan kolmessa rykelmässä kahteen eri suuntaan. Osalla proteiineista on hemagglutinaatioaktiivisuutta, jonka mukaan HA-geenit on nimetty. Diagnostiikassa hiirikokeet ovat paljolti väistyneet uusien menetelmien tieltä, vaikka ne ovatkin yhä ainoa varma keino todeta toksiinin aktiivisuus. Immunologisista menetelmistä ELISA:a on paljon hyödynnetty C- ja D-tyypeillä. Detektioon on käytetty PCR:ää, mutta modernimpien geeniteknisten tyypitysmenetelmien osalta ei ole vielä julkaistuja tutkimustuloksia C- ja D-tyypeiltä. Sen sijaan ihmisbotulismia aiheuttavia tyyppejä on paljon tutkittu mm. ribotyypityksellä, PFGE:llä ja AFLP:llä.
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Investigating airborne virus transmission in public spaces using a non-pathogenic model virus phi 6 (2021)The COVID-19 pandemic of 2019 has had a huge impact on the hospitality industry, decreasing production by 35.4% in Q4 of 2020. To keep the industry functional, new safety solutions have to be studied and developed for mitigation of the pandemic. In this study, airborne transmission of viruses in an indoor space was studied, and air purifiers and space dividers were tested as potential intervention methods against SARS-CoV-2 by using a non-pathogenic model virus phi 6. Filtered air purifiers were found to work as a possible solution for the mitigation of viruses spreading through aerosols in public spaces such as restaurants, however, the positioning of the devices is crucial, as the air flow to them may increase the concentration of viruses locally. Space dividers were found to increase the possibility of infection via aerosols. Other types of air purifiers were also tested: an ionizer prototype and a hydroxyl radical emitting unit, of which the ionizer prototype proved to be efficient in reducing the virus concentrations in the air. Most importantly, it was confirmed that enveloped viruses resembling coronaviruses are capable of spreading via aerosol transmission indoors.
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Investigating airborne virus transmission in public spaces using a non-pathogenic model virus phi 6 (2021)The COVID-19 pandemic of 2019 has had a huge impact on the hospitality industry, decreasing production by 35.4% in Q4 of 2020. To keep the industry functional, new safety solutions have to be studied and developed for mitigation of the pandemic. In this study, airborne transmission of viruses in an indoor space was studied, and air purifiers and space dividers were tested as potential intervention methods against SARS-CoV-2 by using a non-pathogenic model virus phi 6. Filtered air purifiers were found to work as a possible solution for the mitigation of viruses spreading through aerosols in public spaces such as restaurants, however, the positioning of the devices is crucial, as the air flow to them may increase the concentration of viruses locally. Space dividers were found to increase the possibility of infection via aerosols. Other types of air purifiers were also tested: an ionizer prototype and a hydroxyl radical emitting unit, of which the ionizer prototype proved to be efficient in reducing the virus concentrations in the air. Most importantly, it was confirmed that enveloped viruses resembling coronaviruses are capable of spreading via aerosol transmission indoors.
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(2022)The tRNA-derived fragments (tsRNAs) are known to play a role in protein translation and post-transcriptional regulation. Viruses exploit the cellular machinery of the host for their replication and therefore the formation of tRNA-derived fragments could be one mechanism utilized by the virus for completing the infection cycle. Virus-induced tRNA-derived fragments have so far been found to suppress the antiviral responses of the host or to favor viral protein translation. However, the biogenesis of tsRNAs, their virus specificity, as well as their putative regulatory roles during infection are still mainly unknown. Research into the roles of tsRNAs in viral infection has enormous potential to reveal novel regulatory functions of tsRNAs and shed light on the mechanisms which viruses utilize to hijack the cellular translation machinery. This Master’s thesis project aimed to investigate the possible regulatory role and the origin of infection-induced tRNA-fragments in Shewanella glacialimarina TZS-4T. S. glacialimarina was infected with Shewanella phage isolate 1/4 and total RNA was isolated from culture samples collected at different timepoints after infection. Additionally, to assess the specificity of the phenomena, S. frigidimarina and S. baltica, two evolutionary close relatives of S. glacialimarina, were also infected with Shewanella phage isolate 1/4. The formation of fragments was found to be dynamic and specific to S. glacialimarina. The observed fragments were further purified from the total RNA and sequenced using an adapted protocol for sequencing library preparation to identify the origin of the fragments. As a result of this thesis, the adapted protocol was further optimized for the fragment isolation, yet the full identification of the sequences was not achieved within the timeframe of this project.
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(2022)The tRNA-derived fragments (tsRNAs) are known to play a role in protein translation and post-transcriptional regulation. Viruses exploit the cellular machinery of the host for their replication and therefore the formation of tRNA-derived fragments could be one mechanism utilized by the virus for completing the infection cycle. Virus-induced tRNA-derived fragments have so far been found to suppress the antiviral responses of the host or to favor viral protein translation. However, the biogenesis of tsRNAs, their virus specificity, as well as their putative regulatory roles during infection are still mainly unknown. Research into the roles of tsRNAs in viral infection has enormous potential to reveal novel regulatory functions of tsRNAs and shed light on the mechanisms which viruses utilize to hijack the cellular translation machinery. This Master’s thesis project aimed to investigate the possible regulatory role and the origin of infection-induced tRNA-fragments in Shewanella glacialimarina TZS-4T. S. glacialimarina was infected with Shewanella phage isolate 1/4 and total RNA was isolated from culture samples collected at different timepoints after infection. Additionally, to assess the specificity of the phenomena, S. frigidimarina and S. baltica, two evolutionary close relatives of S. glacialimarina, were also infected with Shewanella phage isolate 1/4. The formation of fragments was found to be dynamic and specific to S. glacialimarina. The observed fragments were further purified from the total RNA and sequenced using an adapted protocol for sequencing library preparation to identify the origin of the fragments. As a result of this thesis, the adapted protocol was further optimized for the fragment isolation, yet the full identification of the sequences was not achieved within the timeframe of this project.
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(2010)The properties and evaluation methods of viili, the actions and interactions of viili starters in milk and bacteriophages of the viili starters were reviewed. The aim of the experimental study was to explore whether it was possible to make viili with single strain starters and combine them just before adding the starter to the milk. A new, second viili starter was made from the new strains. The success of the new starters was evaluated by sensory evaluation and by analysing the texture and chemical properties of viili. The starter strains were cultivated in a bioreactor, concentrated by a centrifuge and frozen at –75 °C. The starter strains were combined approx. 1 day before the viili production. The sensory evaluation of the viili was performed by groups of 3 to 6 persons. The texture (consistency, firmness and cohesiveness) of the viili and chemical analysis were made. The results of the sensory analysis were analysed statistically and new strain combinations were formulated based results. The viilis made by the traditional viili starter strains were evaluated by the triangle test (n = 10–11) and the second viili starter was evaluated by descriptive analysis (n = 8). The texture measurements and chemical analyses were also performed. The viili produced by the second starter was infected by the factory phage samples and the pH was measured. After infecting the viili with phage samples, the viili produced by second starter was acidified to pH 4.5 from 0 to 10 hours later compared to the viili without the phage sample. The viili produced by traditional starter did not acidify when the phage was added. The aroma producers did not grow properly in viili when the starter was made by single strains. The viilis made by the present viili starter strains were not distinguished by the triangle test which meant that the starters are possible to make from single strains. The viilis produced by the second viili starter differed from the viili made by traditional starter by appearance and texture characteristics. There was no difference in taste characteristics between the traditional and new starter.
Now showing items 1-6 of 6