Sanitär- und Kommunaltechnik; Umwelttechnik
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Antimicrobial resistance (AMR) is a global health problem. It is well known that antibiotics can drive evolutionary processes that underlie antimicrobial resistance (AMR) evolution and spread in clinical and environmental settings. In contrast, less is known about the effects of antimicrobial substances that are used as biocides (i.e. disinfectants and preservatives) on AMR evolution and spread. Biocides are present in various settings, interacting with diverse microbial communities. Therefore, it is crucial to evaluate their role in the evolution and dissemination of antimicrobial resistance. Biocides occur in a wide range of concentrations in various environmental settings. By examining how the various concentrations affect selection mechanisms, we gain insights into potential developments related to antimicrobial resistance. The aim of this PhD thesis is to investigate the effects of biocides on processes underlying resistance evolution. Specifically, the work focused on key mechanisms for resistance spread, resistance evolution, and the effect of selection pressures on evolved resistance mechanisms. The thesis is structured around three major objectives: (i) to determine the effect of biocides on the evolution of resistance by affecting the rate of occurrence of de novo mutations, (ii) to determine the effect of biocides on the spread of resistance genes by modifying the rate of horizontal gene transfer (HGT) processes, and (iii) to investigate the selective drivers of the emergence of antimicrobial resistance in adaptive laboratory evolution (ALE) experiments. De-novo mutations are spontaneous mutations that occur at a certain rate in microorganisms. The effect of biocides at subinhibitory environmentally relevant concentrations on the mutation rate in Acinetobacer baylyi, Bacillus subtilis and Escherichia coli was assessed with the fluctuation assay. The results showed that biocides affected mutation rates in a species and substance dependent matter. The bisbiguanide chlorhexidine digluconate, the quaternary ammonium compound didecyldimethylammonium chloride, the metal copper, the pyrethroid-insecticide permethrin, and the azole-fungicide propiconazole increase mutation rates in E. coli, whereas no increases were identified for B. subtilis and A. baylyi. Horizontal gene transfer refers to diverse mechanisms that mediate the transfer of mobile genetic elements between microorganisms. This work focused on conjugation and transformation. Conjugation is a process whereby a conjugative plasmid is transferred from a donor cell to a recipient cell. Transformation is a process whereby exogenous donor DNA is taken up into a recipient cell and integrated into the recipient’s’ genome. The effects of subinhibitory environmentally relevant biocide concentrations on the conjugation rate of E. coli and the transformation rate of the naturally competent organisms A. baylyi in were assessed. The results showed that benzalkonium chloride (BAC), chlorhexidine and permethrin increased conjugation in E. coli, while none of the biocides increased transformation rates in A. baylyi. To further understand the molecular mechanisms underlying the effects on mutation and conjugation rates, I investigated the induction of the RpoS-mediated general stress and the RecA-linked SOS response upon biocide exposure. The results show a link between the general stress and the SOS response with increased rates of mutation and conjugation, but not for all biocides. One major approach to study the evolutionary response of bacteria to antimicrobials are ALE experiments with growth at subinhibitory concentrations linked to serial subculturing over many generations. Such experiments have been used to study resistance evolution to antibiotics and biocides. However, previous work showed that adaptation to biocide stress may be mediated by different evolutionary drivers. Here, I investigated the contributions of evolution for increased survival as opposed to improved growth in ALE experiments with E. coli exposed to subinhibitory BAC concentrations. Two distinct evolutionary treatments selecting for survival only or survival and growth led to specific evolutionary adaptations apparent in the phenotypes and genotypes of the evolved populations. Populations growing in the presence of BAC evolved increased fitness in the presence of BAC associated with higher resistance to BAC and cross-resistance to antibiotics, while this was not the case for populations evolving for increased survival only. Genotypic characterization by whole genome sequencing of the evolved populations revealed parallelism in mutated genes among replicate populations and distinct differences across treatments. Treatments selecting for survival and growth showed mutations in stress response related genes (hslO and tufA), while selection for survival led to mutations in genes for metabolic regulation (cyaA) and cellular structure (flagella fliJ). In summary, this thesis shows that biocides affect AMR evolution and emphasizes the importance of understanding of how biocides impact the molecular and evolutionary process that underlie AMR evolution.
Advanced light weight applications like aircrafts and wind turbine blades are made of fibre reinforced plastics (FRP) with continuous fibre reinforcement and must withstand a high thermo-mechanical cyclic loading. The quality of the fibre matrix interface has a high impact on the fatigue life and was continuously improved over the years since the 50th. The fatigue life of glass fibre reinforced plastics (GFRP) used in aircraft industry is 10 to 100 times higher compared to glass fibre non crimp fabrics used for wind turbine blades.
To assure a constant and reliable high quality and strength of reinforcement fibres, synthetic fibre production is state of the art (CF, GF). There is a need for recycling GFRP and CFRP waste due to the upcoming use. Pyrolysis and solvolysis are more expensive than the mechanical route however enable a more sustainable recycling. Natural fibres and recycled synthetic fibres have a high scatter in quality and strength. Hence it is a challenge to optimize the production / recycling processes to get a reliable quality for any demanding (second life) application.
Chemical routes for using renewables resources and recycling, is going to be a good approach especially for polymer-matrix systems to get 100% quality (back) compared to the state of the art.
Finally, a proper design, life-time extension and repair is preferable to recycling to keep the carbon footprint as low as possible.
Revolutionizing our polymer industry for adaption to a sustainable carbon circular economy has become one of today’s most demanding challenges. Exploiting renewable resources to replace fossil-fuel—based plastics with biopolymers such as poly(lactic acid) (PLA) is inevitable while using waste streams as a raw material resource at least is promising. When it comes to using PLA as technical polymer, its high flammability must be addressed by flame retardants compatible with the thermoplastic processing of PLA and its compostability. This study proposes microalgae enriched with phosphorus from wastewater (P-Algae) as an elegant way towards a kind of sustainable organophosphorus flame retardant. The concept is demonstrated by investigating the processing, pyrolysis, flammability, and fire behavior of PLA/P-Algae, while varying the P-Algae content and comparing P-Algae with four alternative bio-fillers (phosphorylated lignin, biochar, thermally treated sewage sludge, and metal phytate) with different P-contents as meaningful benchmarks.
Stable metal isotopes receive increasing attention as medical biomarkers due to their potential to detect changes of the metal metabolism related to disease. Potential mechanisms causing isotope fractionation include biological processes that involve redox- or bond-forming reactions and interaction of metals during transmembrane import and export. In order to advance our understanding of the underlying processes responsible for isotope fractionation between normal and diseased cells, we need in situ, spatially resolved methods. Despite its frequent use, laser ablation - multi-collector - inductively coupled plasma mass spectrometry (LA-MC-ICPMS) analysis of biological material is severely limited by the scarcity of matrix-matched standards. Such matrix-matched standards are necessary to correct for instrumental sources of isotope fractionation such as particle size distribution, ablation physics and differential ionization.
Copper stable isotopes have proven to be a particularly powerful tool to identify differences in isotope composition between tumors and healthy tissue suggesting application in cancer diagnosis [1, 2]. To further our knowledge of Cu isotope fractionation processes induced by diseases we have developed gelatin-based bracketing standards allowing to correct instrumentally induced isotope fractionation during LA-MC-ICPMS analysis. Since gelatin properties resemble properties of protein-rich cellular material, they mimic biological matrices and their ablation behaviour. Hence, gelatin standards are spiked with known amounts of Cu stable isotopes of a known Cu isotope composition and used as matrix-matched bracketing standard. A Ni reference solution was aspirated to the plasma to allow for mass bias correction and laser energy densities were below the glass ablation threshold. The method achieved reproducibilities of better than 0.10‰ (2SD) for inorganic reference materials and reproducibilities of better than 0.17‰ (2SD) for biological reference materials. The developed routine is tested on biomedical samples and the in situ Cu isotope data will be presented.
The synergistic behavior of different silicon compounds is investigated in flame retardant biocomposites with aluminum trihydroxide (ATH) as the main flame retardant. The paper shows a new approach towards sustainable biocomposites through the implementation of thermoplastic starch (TPS), leather fibers from industrial waste streams, and non-hazardous flame retardants and synergists. In these multicomponent systems, the different components address different modes of action in the fire scenario. When ATH is partially substituted by glass frits or layered silicates, fire performance is enhanced without changing the total amount of filler in the polymer. In a biocomposite with 25 phr of fiber and 90 phr of ATH, substituting 5 phr of ATH for layered silicates increased the LOI from 31.5 vol % to 34.8 vol %, decreased the peak of heat release by 20%, and increased the UL 94 rating from V-1 to V-0.
Non-specific Gd-based contrast agents (GBCAs) have long been routinely used in clinical magnetic resonance imaging (MRI). However, the interaction of such contrast agents with tissue components is not yet fully understood.
Alongside cells, the extracellular matrix (ECM) is an important component of mammalian tissue. It is a three-dimensional network of macromolecules that provides structural and biochemical support to the surrounding cells. Many diseases, including inflammation, fibrosis, and tumour invasion, are associated with characteristic ECM changes. The ECM consists of structural proteins (e.g., collagen, elastin) and proteoglycans, which are composed of glycosaminoglycans (GAGs) covalently linked to a protein core. GAGs are long, linear polysaccharides consisting of repeated disaccharide units widely varying in molecular mass, disaccharide structure, and sulfation degree. Characteristic of GAGs is their ability to form complexes with cations such as lanthanides. Thus, GAGs could be a potential binding partner for GBCA molecules as a whole or for dechelated Gd.
Currently, there are still many unanswered questions about the interaction of contrast agents with ECM components. This study therefore investigated the uptake and distribution of different GBCAs in spheroids that mimic biological tissue and have different ECM expressions.
Chinese hamster ovary (CHO) cells and GAG-depleted CRL-2242 cells were used to prepare spheroids. These were then incubated for several minutes with gadolinium chloride and various linear and macrocyclic GBCAs. Cryosections of the spheroids were used for imaging measurements with a low-dispersion laser ablation system coupled to an inductively coupled plasma time-of-flight mass spectrometer (LA/ICP-ToF-MS). Gelatine doped with multi-element solutions was used for matrix-matched quantification of Gd and other relevant elements such as Cu, Fe and Zn.
Although all spheroids were incubated with identical Gd concentrations, significant differences in the amount of Gd taken up were observed. Gadolinium chloride is absorbed more strongly than the contrast agents and accumulates mainly in the outer regions of the spheroids. In contrast, after incubation with the linear and macrocyclic contrast agents, Gd is detected in the interior of both types of spheroids.
Guaranteeing safety and security of citizens requires a significant effort and innovative tools from national and international agencies and governments, especially when it comes to the field of explosives detection. The need to detect Improvised Explosive Devices (IEDs) and Home-made Explosives (HMEs) at a point of suspicion, has grown rapidly due to the ease with which the precursors can be obtained and the reagents synthesised. The limited availability of immunoanalytical tools for HME detection presents an opportunity for the development of new devices, which enable a rapid detection and recognise the target analyte with high specificity and sensitivity. In this work, we introduce an optical biosensor for highly specific and sensitive HME detection. The immunoassay system is placed in a hydrogel environment permeable to the analyte and transparent to light interrogating the fluorescently labelled antibodies. The readout of the immunoanalytical system is realized with Supercritical Angle Fluorescence (SAF), an advanced microscopy technique. To accomplish this, we made use of recent, commercial high resolution (< 22 µm) Liquid Crystal Display 3D printers to fabricate a parabolic optical element with high refractive index (RI>1.5) and transmission values (>90%) from photo-resin. Aiming at a new generation of sensors, which not only can meet the requirements of trace detection, but can also be used for substance identification, the combination of immunoanalytical recognition with SAF detection offers a modularity and versatility that is principally well suitable for the measurements of target analytes at trace levels.
The global plastic industry relies on fossil-based materials, presenting environmental challenges. A sustainable polymer namely poly(limonene carbonate) (PLimC), made of limonene and CO2 as two monomers from non-food sources, shows advances in various applications where additives such as flame retardants (FRs) are crucial to comply with fire safety measures.
The variety of FRs is wide, and therefore the approach involved conducting a comparative study of four different halogen-free flame retardant systems that are conventionally used in polycarbonates and polyolefins to understand which FR enhances the flame resistance of PLimC most effectively. The primary task of the project is to conduct experimental evaluations to analyze the thermal properties, flammability, and fire behavior of each system. This data will offer valuable insights towards the advancement of safer and more sustainable materials.
The classification of incineration bottom ash (IBA) as hazardous or non-hazardous according to ecotoxic hazard property HP14 is still under debate. In this context, only the compounds of Zn and Cu with the hazard statement code H410 are of relevance. With an approach based on the grouping of substances, it was shown that such substances are either readily water-soluble or slightly and sparingly soluble. The concentrations of readily soluble Cu and Zn compounds in IBA are far below the cut-off value of 0.1%. Slightly and sparingly soluble Zn and Cu compounds could be quantified in the first fraction of a four-step sequential extraction procedure. With the results from the complete sequence, the dimensionless synthesis toxicity index (STI) was calculated and was in the range of 494 to 1218 for the four investigated IBA samples. It was concluded that IBA can usually be classified as non-hazardous.
The classification of incineration bottom ash (IBA) as hazardous or non-hazardous according to ecotoxic hazard property HP14 is still under debate. In this context, only the compounds of Zn and Cu with the hazard statement code H410 are of relevance. With an approach based on the grouping of substances, it was shown that such substances are either readily water-soluble or slightly and sparingly soluble. The concentrations of readily soluble Cu and Zn compounds in IBA are far below the cut-off value of 0.1%. Slightly and sparingly soluble Zn and Cu compounds could be quantified in the first fraction of a four-step sequential extraction procedure. With the results from the complete sequence, the dimensionless synthesis toxicity index (STI) was calculated and was in the range of 494 to 1218 for the four investigated IBA samples. It was concluded that IBA can usually be classified as non-hazardous.