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  <doc>
    <id>2178</id>
    <completedYear/>
    <publishedYear/>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber>39</pageNumber>
    <edition/>
    <issue/>
    <volume/>
    <type>masterthesis</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>1</belongsToBibliography>
    <completedDate>2024-09-24</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Molecular mechanisms of biocide-induced antibiotic tolerance in bacteria</title>
    <abstract language="eng">Antimicrobial resistance represents a significant and imminent threat to global health, according to the World Health Organization (WHO). The emergence of resistance in bacteria and other microorganisms is a consequence of the sustained and excessive utilisation of antimicrobial agents. Considering these developments, concerns are rising regarding the potential for cross-resistance between biocides and antibiotics.&#13;
There are mechanisms, that affect the susceptibility of microorganisms to both classes of antimicrobial agents. Three modes of reduced susceptibility are distinguished between resistance, tolerance and persistence. Resistance describes a decrease of susceptibility and the ability to grow in presence of concentrations, that inhibit closely related strains. Tolerance is described as a loss of susceptibility and an increase in survival of the entire population. Persistence refers to a subpopulation that is able survive due to changes in gene expression, often without genetic alterations.&#13;
In previous experiments conducted at BAM, exposure to a subinhibitory concentration of glutaraldehyde was observed to result in enhanced survival against antibiotics and an induction of prolonged lag. A prolongation of the lag time is associated with antibiotic tolerance and increased survival. Using transcriptomics two genes of interest were discovered: yadV, a putative fimbrial chaperone and yjfL, an inner membrane protein. The genes and their role in lag and antibiotic survival are not well studied. The aim of this thesis is to investigate, the role of the genes in lag and antibiotic tolerance.&#13;
To conduct the experiments, a few mutants were obtained.: I) a knockout mutant, II) an overexpression mutant and III) a fluorescent reporter mutant of yadV and yjfL, together with respective controls. The overexpression and reporter mutant were transformed into the wild type E. coli MG1655 used in the previous experiments.&#13;
The minimal inhibitory concentration (MIC) and the minimal bactericidal concentration (MBC)&#13;
were determined for the knockout mutants and the wildtypes. The knockout of the genes of&#13;
interest does not show a significant difference compared to the wild type.&#13;
Next, time-kill-curves for the knockout and overexpression mutants were gathered in the presence&#13;
of lethal doses of antibiotics. The knockout mutants were induced with subinhibitory concentrations of glutaraldehyde to assess the effect of the mutations on antibiotic tolerance. The knockout mutants do not indicate a difference to the wildtypes again, whereas the overexpression of yadV was observed to induce tolerance.&#13;
Scanlag experiments were performed to examine the distribution of single-cell lag-times and detect changes, as an extended lag-time promotes survival. The prolonged lag was detected for knockout mutants and the wildtypes. This suggests the tolerance induced by glutaraldehyde is independent of yadV and yjfL. Overexpression mutants exhibit the same lag as the wildtype.&#13;
While the overexpression of yadV facilitates tolerance, it is not tolerance by lag.&#13;
A different approach was employed for the reporter mutants. The cells were compared with cells exposed to a sublethal concentrations of glutaraldehyde, to detect heterogeneity. A heterogenous expression may indicate a tolerant subpopulation, that functions as persisters. Such a subpopulation was identified for yadV as well as the positive control.&#13;
The knockout of the genes does not impact the survival against antibiotics. However, the overexpression of yadV impacts and promotes the survival.</abstract>
    <enrichment key="opus.source">publish</enrichment>
    <licence>Keine Lizenz vergeben. Es gilt das deutsche Urheberrecht.</licence>
    <author>Roxana Rebecca Elin Heise</author>
    <series>
      <title>Abschlussarbeiten 2024</title>
      <number>63</number>
    </series>
    <subject>
      <language>deu</language>
      <type>uncontrolled</type>
      <value>Escherichia coli</value>
    </subject>
    <subject>
      <language>deu</language>
      <type>uncontrolled</type>
      <value>Antibiotikatoleranz</value>
    </subject>
    <subject>
      <language>deu</language>
      <type>uncontrolled</type>
      <value>Glutaraldehyd</value>
    </subject>
    <collection role="institutes" number="02">FB2: Ingenieurwissenschaften II - Technik und Leben</collection>
    <collection role="studycourse" number="">Life Science Engineering</collection>
    <thesisPublisher>Hochschule für Technik und Wirtschaft Berlin</thesisPublisher>
    <thesisGrantor>Hochschule für Technik und Wirtschaft Berlin</thesisGrantor>
  </doc>
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