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Papers by Thomas Schwartz

Bacterial colonization of surfaces and interfaces has a major impact on various areas in-cluding ... more Bacterial colonization of surfaces and interfaces has a major impact on various areas in-cluding biotechnology, medicine, food industries, and water technologies. In most of these areas biofilm development has a strong impact on hygiene situations, product quality, and process efficacies. In consequence, biofilm manipulation and prevention is a fundamental issue to avoid adverse impacts. For such scenario online, non-destructive biofilm monitor-ing systems become important in many technical and industrial applications. This study re-ports such a system in form of a microfluidic sensor platform based on the combination of electrical impedance spectroscopy and amperometric current measurement, which allows sensitive online measurement of biofilm formation and activity. A total number of 12 parallel fluidic channels enable real-time online screening of various biofilms formed by different Pseudomonas aeruginosa and Stenotrophomonas maltophilia strains and complex mixed population biofi...

Environment International, 2020

and Norway) was carried out in two consecutive years (2015 and 2016). This is the first study of ... more and Norway) was carried out in two consecutive years (2015 and 2016). This is the first study of this kind performed at an international level. Within the 53 antibiotics monitored 17 were detected at least once in the final effluent of the WWTPs, i.e.: ciprofloxacin, ofloxacin, enrofloxacin, orbifloxacin, azithromycin, clarithromycin, sulfapyridine, sulfamethoxazole, trimethoprim, nalidixic acid, pipemidic acid, oxolinic acid, cefalexin, clindamycin, metronidazole, ampicillin, and tetracycline. The countries exhibiting the highest effluent average concentrations of antibiotics were Ireland and the southern countries Portugal and Spain, whereas the northern countries (Norway, Finland and Germany) and Cyprus exhibited lower total concentration. The antibiotic occurrence data in the final effluents were used for the assessment of their impact on the aquatic environment. Both, environmental predicted no effect concentration (PNEC-ENVs) and the PNECs based on minimal inhibitory concentrations (PNEC-MICs) were considered for the evaluation of the impact on microbial communities in aquatic systems and on the evolution of antibiotic resistance, respectively. Based on this analysis, three compounds, ciprofloxacin, azithromycin and cefalexin are proposed as markers of antibiotic pollution, as they could occasionally pose a risk to the environment. Integrated studies like this are crucial to map the impact of antibiotic pollution and to provide the basis for designing water quality and environmental risk in regular water monitoring programs.

Scientific Reports, 2019

Conventional wastewater treatment is not sufficient for the removal of hygienically relevant bact... more Conventional wastewater treatment is not sufficient for the removal of hygienically relevant bacteria and achieves only limited reductions. This study focuses on the reduction efficiencies of two semi-industrial ultrafiltration units operating at a large scale municipal wastewater treatment plant. In total, 7 clinically relevant antibiotic resistance genes, together with 3 taxonomic gene markers targeting specific facultative pathogenic bacteria were analysed via qPCR analyses before and after advanced treatment. In parallel with membrane technologies, an ozone treatment (1 g ozone/g DOC) was performed for comparison of the different reduction efficiencies. Both ultrafiltration units showed increased reduction efficiencies for facultative pathogenic bacteria and antibiotic resistance genes of up to 6 log units, resulting mostly in a strong reduction of the bacterial targets. In comparison, the ozone treatment showed some reduction efficiency, but was less effective compared with ult...

Journal of Physics: Conference Series, 2013

Synchrotron-based phase contrast tomography (holotomography) and scanning hard X-ray fluorescence... more Synchrotron-based phase contrast tomography (holotomography) and scanning hard X-ray fluorescence microscopy (SXFM) are combined to characterize the three-dimensional (3D) structural and corresponding elemental distribution of bacterial biofilms of Pseudomonas aeruginosa. Samples were fixed without contrast agents or microtomal sectioning. Within an intact microbial community single bacteria are clearly resolved, and their morphology can be directly visualized together with the elemental content. Such 3D set of complementary information at cellular level is essential for gaining a deeper understanding of biofilm evolution aiming to develop potential strategies on biofilm growth control and prevention.

Frontiers in microbiology, 2017

Seven wastewater treatment plants (WWTPs) with different population equivalents and catchment are... more Seven wastewater treatment plants (WWTPs) with different population equivalents and catchment areas were screened for the prevalence of the colistin resistance gene mcr-1 mediating resistance against last resort antibiotic polymyxin E. The abundance of the plasmid-associated mcr-1 gene in total microbial populations during water treatment processes was quantitatively analyzed by qPCR analyses. The presence of the colistin resistance gene was documented for all of the influent wastewater samples of the seven WWTPs. In some cases the mcr-1 resistance gene was also detected in effluent samples of the WWTPs after conventional treatment reaching the aquatic environment. In addition to the occurrence of mcr-1 gene, CTX-M-32, blaTEM, CTX-M, tetM, CMY-2, and ermB genes coding for clinically relevant antibiotic resistances were quantified in higher abundances in all WWTPs effluents. In parallel, the abundances of Acinetobacter baumannii, Klebsiella pneumoniae, and Escherichia coli were quant...

2008 IEEE 35th International Conference on Plasma Science, 2008

Summary form only given. Wastewater from hospitals carries large number of pathogenic and increas... more Summary form only given. Wastewater from hospitals carries large number of pathogenic and increasingly antibiotic resistant bacteria, which could spread in the environment. The pulsed electric field (PEF) treatment of wastewater as a non-chemical disinfection method is a suitable alternative method for reducing this bacterial freight. In the literature it was figured out, that continuous flow PEF treatment reduces more effectively bacterial contamination than batch reactor treatment. One explanation is that the heat generated during the PEF treatment in a continuous flow reactor is positively affecting the bacterial reduction. Depending on the PEF treatment energy, outlet temperatures of more than 70degC were achieved. Consequently, bacterial reduction depends on the initial wastewater temperature and on the electrical dissipated treatment energy. In our study we analysed the bacterial reduction depending on temperature. Filtered wastewater samples (from a wastewater purification plant) were inoculated with the Enterococcus faecium (BRE; Strain 211, Mainz) and exposed to different PEF treatments at 40, 50 and 60degC. The lethal treatment temperature of the Enterococcus faecium by heat treatment over 3-4 min is around 56degC. Treatment with 60degC for the same duration provokes a bacterial reduction of 4 log. Simultaneous treatments of inoculated wastewater samples with PEF and heating (40, 50 and 60degC) reduced the bacterial contamination over the expected effect, calculated as a sum of effects induced from both treatments. This is an indication for a synergistic effect induced through the simultaneous treatment with PEF and heat. In all experiments the specific energy was kept constant by adjusting the number of pulses. At 2degC, the bacterial reduction saturates already for PEF treatments with specific energies higher than 120 J/ml. At higher temperatures (over 40degC), the bacterial reduction increased until the complete reduction (ov- - er 8 log) was achieved at 60degC. To separate the thermal effect from the PEF effect, samples were treated first with PEF in a batch chamber and afterwards, about 30 s later, by heating over 4 min. No significant variation of the efficiency of bacterial reduction compared to the simultaneous treatment was found. These results show that the duration of cell membrane damage, is far longer as the assumed healing time (mus-range). This finding can be used for further optimization of the PEF treatment in continuous flow.

The Handbook of Environmental Chemistry, 2015

The increase of antibiotic resistance in clinical settings but also in wastewater treatment plant... more The increase of antibiotic resistance in clinical settings but also in wastewater treatment plants is of increasing concern to human health. The goal of this chapter is to investigate the potential of different tertiary wastewater treatment technologies as to the reduction of the amount of antibiotic-resistant bacteria and genes in wastewater effluents. Molecular- and cultivation-based techniques are reported in the current scientific literature for the analysis of bacterial communities and especially opportunistic pathogenically bacteria in wastewater and after different levels of disinfection processes. Additionally, the presence of antibiotic resistance genes (vanA, mecA, ampC, ermB, blaVIM, tetM) and phenotypic resistance to ciprofloxacin, cefuroxime, trimethoprim, ofloxacin, and tetracycline were analyzed to characterize the impact of different wastewater treatments and advanced oxidation processes (AOPs) on the effluent antibiotic resistance patterns. The examination of the application of advanced oxidation and photo-driven technologies showed significant discrepancy among the removal of different bacterial families as well as bacterial species in wastewater.

The Journal of Membrane Biology, 2013

An important issue for an economic application of the pulsed electric field treatment for bacteri... more An important issue for an economic application of the pulsed electric field treatment for bacterial decontamination of wastewater is the specific treatment energy needed for effective reduction of bacterial populations. The present experimental study performed in a field amplitude range of 40 [ E [ 200 kV/cm and for a suspension conductivity of 0.01 = j e [ 0.2 S/m focusses on the application of short pulses, 25 ns [ T [ 10 ls, of rectangular, bipolar and exponential shape and was made on Pseudomonas putida, which is a typical and widespread wastewater microorganism. The comparison of inactivation results with calculations of the temporal and azimuthal membrane charging dynamics using the model of Pauly and Schwan revealed that for efficient inactivation, membrane segments at the cell equator have to be charged quickly and to a sufficiently high value, on the order of 0.5 V. After fulfilling this basic condition by an appropriate choice of pulse field strength and duration, the log rate of inactivation for a given suspension conductivity of 0.2 S/m was found to be independent of the duration of individual pulses for constant treatment energy expenditure. Moreover, experimental results suggest that even pulse shape plays a minor role in inactivation efficiency. The variation of the suspension conductivity resulted in comparable inactivation performance of identical pulse parameters if the product of pulse duration and number of pulses was the same, i.e., required treatment energy can be linearly downscaled for lower conductivities, provided that pulse amplitude and duration are selected for entire membrane surface permeabilization.

Chemosphere, 2009

During the last years the pulsed electric field (PEF) method entered several fields of applicatio... more During the last years the pulsed electric field (PEF) method entered several fields of application. A promising application is the decontamination of hospital wastewater effluents, which are loaded with pathogenic and increasingly with antibiotic-resistant bacteria. For this study, Pseudomonas putida suspended in buffer solution or wastewater from university hospital was used as reference strain. To prove whether the descendent of the survival bacteria develop an adaptation to electric field, surviving PEF treated bacteria were recultivated and pulsed in serial experiments with 10 pulses (100 kV cm À1 and 600 ns pulse duration). This procedure was repeated for 30 generations. The inactivation rate was calculated with 3.5 ± 0.8 log of colony forming units and remained constant over 30 cycles. Investigations of the variable intergenic spacer region of the ribosomal operon demonstrated no visible changes in this highly variable part of the genome structure during the serial PEF treatment experiments. The mutagenicity of PEF treated hospital wastewater, buffer solutions and tap water was analyzed by the umu-test. Most hospital wastewater samples exhibit a considerable genotoxicity already before PEF treatment, but this was not increased by the PEF treatment, not even for higher treatments energies over 250 J mL À1. No genotoxicity was induced in buffer solutions and tap water by PEF treatment. This study supports, that PEF treatment is a sustainable non-chemical method for bacterial decontamination without any adverse effects.

FEMS Microbiology Ecology, 2006

Real-time quantification of Pseudomonas aeruginosa was performed in various wastewater systems in... more Real-time quantification of Pseudomonas aeruginosa was performed in various wastewater systems including clinical, municipal wastewaters and inflow from a wastewater treatment plant. The highest concentrations of P. aeruginosa-specific targets were detected in clinical wastewaters. Limitations of the detection system resulting from inhibition or cross-reaction were identified. Ciprofloxacin-resistant P. aeruginosa strains were isolated after specific enrichment from clinical and municipal wastewaters. In some cases they were also cultivated from effluent of a wastewater treatment plant, and from its downstream river water. A total of 119 isolates were phenotypically characterized as ciprofloxacin-resistant via antibiogram testing. Subsequently, the fluoroquinolone-resistance-mediating mutations in the genes gyrA codon positions 83 and 87, gyrB codon position 466 and parC codon positions 87 and 91 were determined by mini-sequencing. Ciprofloxacin resistance was mainly associated with mutations in gyrA codon position 83 and parC mutation in codon positions 87 or 91 of the bacterial gyrase and topoisomerase II genes. All ciprofloxacin-resistant P. aeruginosa strains were compared with genotypes from clinical data of fluoroquinolone-resistant P. aeruginosa infections. The results were in agreement with data from clinical analyses, with the exception that no gyrA 87 and no gyrB mutations were found in ciprofloxacin-resistant P. aeruginosa wastewater isolates.

Introduction Microbial biofilms are an extremely successful way of life. Bacteria and fungi benef... more Introduction Microbial biofilms are an extremely successful way of life. Bacteria and fungi benefit in this symbiotic life form of metabolic exchange, protection and genetic flexibility. They produce a matrix of organic molecules in which they are embedded and which offers new habitats to other organisms, such as other bacteria or fungi. Biofilms cannot be avoided to colonize surfaces in unsterile habitats. So, they can be found everywhere in nature and in technical systems, but they play an ambivalent role. On the one hand biofilms are essential to degrade and transform water contaminations, but on the other hand they can diminish product qualities and damage capital equipment. Biofilms can cover medical equipment such as catheters and pathogenic bacteria, which may be living in the biofilms, are a continuous source of infec tion of the patients. In addition, the metabolism of the biofilm microorganisms may change the composition of the fluids or contaminate them with their product...

Frontiers in microbiology, 2018

The occurrence of new chemical and microbiological contaminants in the aquatic environment has be... more The occurrence of new chemical and microbiological contaminants in the aquatic environment has become an issue of increasing environmental concern. Thus, wastewater treatment plants (WWTPs) play an important part in the distribution of so-called new emerging pathogens and antibiotic resistances. Therefore, the daily loads released by the WWTP were calculated including a model system for the distribution of these loads within the receiving water body. UV-, as well as ozone-treatment in separate or in combination for wastewater treatment were under investigation aiming at the reduction of these loads. Here, the impact of these treatments on the DNA integrity via antibody staining and PCR efficiencies experiments were included. All three facultative pathogenic bacteria [enterococci (), ), and ()] and seven clinically relevant antibiotic resistance genes (ARGs) ( (methicillin resistance gene), (β- lactame resistance gene), (erythromycine resistance gene), (β- lactame resistance gene), (...

Advanced Healthcare Materials, 2016

Biofilms represent an immense problem in medicine due to their strong drug-resistant properties a... more Biofilms represent an immense problem in medicine due to their strong drug-resistant properties and inherent stress-response activities. Due to the inhomogeneous and very complex architectures of large biofilm aggregates, biofilm studies often suffer from low reproducibility. In this study, an approach to form arrays of homogeneous biofilm microclusters with defined 2D geometries is presented. The method is based on the formation of water-infused hydrophilic porous polymer areas with precise geometries separated by "slippery" lubricant-infused porous surface (SLIPS). Due to the SLIPS' biofilm repellent properties, multiple identical 3D biofilm clusters are formed in the hydrophilic patches that can be used for biofilm screening. Formation of biofilm microcluster arrays of different bacterial strains of Pseudomonas aeruginosa on the SLIPS micropatterns is investigated. Critical parameters influencing minimal adhesive regions for biofilm attachment and minimal SLIPS dimensions to avoid biofilm adhesion are studied. The ability to produce arrays of biofilm microclusters with highly uniform, well-defined shapes opens an opportunity to study interactions of biofilms with various medically relevant factors with a better reproducibility and to investigate the complex biofilm architecture, heterogeneity, and interactions between biofilm subpopulations. extremely resistant to both the immune response and systemic antibiotic treatments, and thus their development is the primary cause of, e.g., implant/catheterassociated infections. [4] Bacterial infection on medical devices such as catheters and artificial prosthetics is a serious ongoing problem in the biomedical area. Of the 2.6 million orthopedic implants used annually only in the United States, ≈110 000 (4.3%) lead to hospital acquired, or nosocomial, infections. [5] When considering all implanted devices, the number of implant-related bacterial infections approaches one million per year. Another serious problem is that antibiotics administered systemically show constantly decreasing efficiency against implant-associated infections. [6] These infections are caused by bacterial adhesion to an implant surface and by formation of bacterial biofilms. Bacteria inside the biofilm cannot be considered as a simple sum of their constituent cells, but as complex differentiated communities with a heterogeneous 3D structure, [7] which benefit from metabolic exchange and genetic flexibility. [8] To some extent, biofilms can be compared with eukaryotic cell spheroids possessing complex 3D architectures and in vivo-like properties making them more relevant for drug screenings. [9] Thus, there is a strong need to develop methods that would allow for highthroughput screening of small 3D biofilm microclusters. Such biofilm aggregates should possess the same dimension and geometry in order to assure reproducibility and comparability. In addition, understanding of the complex biofilm organization, heterogeneity, and 3D architecture is crucial both for the development of advanced antifouling coatings and for utilizing unique biofilm properties in practical applications, ranging from biotechnology to dia gnostics and tissue engineering. A prerequisite for the development of a technology for highthroughput screening of biofilm aggregates and for studying biofilm organization and 3D architecture, however, requires inter alia methods to spatially control biofilm growth in arrays of precise 2D microstructures over several days. Due to the inherent properties of biofilms to adhere to almost any substrate, there are only very few approaches that allow for biofilm patterning and for making biofilm microarrays. [10] When cultivation of biofilms over several days is required, the patterning

The development and functioning of benthic microbial communities in streams is largely dependent ... more The development and functioning of benthic microbial communities in streams is largely dependent on the hydrological conditions. Climate change projections predict that the hydrological characteristics will probably be affected because of the rainfall regime. Hence, rivers from the Mediterranean region will become more similar to those draining arid or desert regions, while temperate streams will suffer of higher water flow

Water research, 2007

Caulobacter crescentus and Aquabacterium commune, both isolated from drinking water, as well as e... more Caulobacter crescentus and Aquabacterium commune, both isolated from drinking water, as well as environmental isolates of Pseudomonas aeruginosa and Enterococcus faecium were treated with different UV fluences to study their capacity to restore induced DNA damages. Here, the induction of a key mechanism of bacterial dark repair, the so-called recA system, was analysed. With newly designed probes, the specific recA mRNA was detected by Northern blot. Additionally, the RecA protein was measured by the Western blot technique using a specific antibody. In drinking water bacteria as well as in opportunistic microorganisms, a specific induction of dark repair mechanisms was found even at UV fluences higher than 400J/m(2), the German standard for UV disinfection. This induction depended on the incubation time after UV treatment. Nevertheless, the UV-induced recA expressions were found to differ in the bacteria under investigation.

Hydrobiologia, 2012

This study evaluates the sequences of biofilm colonization at two stream sites located in differe... more This study evaluates the sequences of biofilm colonization at two stream sites located in different bioclimatic regions (Mediterranean and Central European). Despite of the ecoregional differences, the two selected streams mainly differed by their hydrology and nutrient condition. A range of structural [microbial biomass, nutrient content, extracellular polymeric substances (EPS)-polysaccharide content] and metabolic (extracellular enzyme activities) descriptors were analyzed during the colonization period of 60 days. The succession of bacterial communities was investigated through the 16S rDNA gene analysis and taxonomical identification was used in diatom communities. Differences in algal biomass were not significant between the two stream biofilms, but the bacterial density and aminopeptidase and b-glucosidase activities were higher in the Mediterranean biofilms, probably due to greater coarse particulate organic matter (CPOM) accumulation in the latter. The colonization sequences of algae and bacteria in the biofilms were faster in the Mediterranean stream biofilms and slower and gradual in the Central European stream biofilms. Floods caused disruption in the microbial succession and re-colonization, favouring the reappearance of early colonizing taxa and increasing the community diversity. Biofilms in the Mediterranean stream had a higher amount of early colonizing species (the diatoms Ulnaria ulna and Karayevia clevei and the b-proteobacteria group), as well as higher polysaccharide development in the extracellular polymeric substances (EPS) matrix. These differences could be an adaptation to the marked hydrological changes characteristic of Mediterranean streams. In contrast, the microbial community complexity gradually increased and nutrients and proteins largely accumulated in the Central European biofilms, reflecting the higher hydrological stability as well as the higher nutrient availability.

Environmental Science and Pollution Research, 2013

Sub-inhibitory concentrations of antibiotics, which are found in environmental water systems and ... more Sub-inhibitory concentrations of antibiotics, which are found in environmental water systems and sewage plants due to an increased use in therapeutical and preventive fields, influence bacterial behavior in biofilms. The application of sulfamethoxazole, erythromycin, and roxithromycin induced changes in biofilm dynamics regarding biomass formation, spatial structure and specific gene expression in different Pseudomonas aeruginosa isolates. Exposing multi-resistant environmental isolated strains for 17 h to environmental concentrations of antibiotics or wastewater, directly, an increase in biofilm biomass and thickness could be observed for each strain. Additionally, multiresistant strains responded to the applied growth conditions with changes in transcriptional activity. Here, sub-inhibitory concentrations of macrolides specifically upregulated expression of quorum sensing genes (rhlR, lasI), whereas sulfonamides and municipal wastewater, instead upregulated expression of specific resistant genes (sul1) and efflux pumps (mexD). Antibiotic sensitive isolates demonstrated an overall higher transcriptionally activity, but did not show a specific gene response to the applied exogenous stimuli. Furthermore, the presence of low concentrated antibiotics induced also phenotypical change in the biofilm architecture observed by 3D-imaging.

ACS Applied Materials & Interfaces, 2013

Water research, Jan 11, 2015

Partial Nitritation/Anammox (PN/A) is a well-established technology for side-stream nitrogen remo... more Partial Nitritation/Anammox (PN/A) is a well-established technology for side-stream nitrogen removal from highly concentrated, warm wastewaters. The focus has now shifted to weakly concentrated municipal wastewaters with much lower concentrations and temperatures. The major challenge is the temperature, which ranges from moderate 20 °C in summer to cold 10 °C in winter. For this study, the most frequently used configurations for side-stream applications were exposed to a slow temperature reduction from 20 °C to 10 °C to simulate a realistic temperature gradient. To evaluate the behavior of the different biomasses based on their properties, four lab reactors were operated in two different configurations. Synthetic wastewater was used to avoid side effects of heterotrophic growth. Differences in the response of the different reactor systems to this temperature gradient clearly indicated, that the geometry of the biomass has a major impact on the overall PN/A performance at low tempera...

Microbial Ecology, 2011

Bacterial communities associated with the surfaces of several Mediterranean sponge species (Agela... more Bacterial communities associated with the surfaces of several Mediterranean sponge species (Agelas oroides, Chondrosia reniformis, Petrosia ficiformis, Geodia sp., Tethya sp., Axinella polypoides, Dysidea avara, and Oscarella lobularis) were compared to those associated with the mesohyl of sponges and other animate or inanimate reference surfaces as well as with those from bulk seawater. Denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified bacterial 16S ribosomal RNA genes obtained from the surfaces and tissues of these sponges demonstrated that the bacterial communities were generally different from each other. The bacterial communities from sponges were different from those on reference surfaces or from bulk seawater. Additionally, clear distinctions in 16S rDNA fingerprint patterns between the bacterial communities from mesohyl samples of "highmicrobial abundance (HMA) sponges" and "low-microbial abundance sponges" were revealed by DGGE and cluster analysis. A dominant occurrence of particularly GC-rich 16S ribosomal DNA (rDNA) fragments was found only in the DGGE banding pattern obtained from the mesohyl of HMA sponges. Furthermore, sequencing analysis of 16S rDNA fragments obtained from mesohyl samples of HMA sponges revealed a dominant occurrence of spongeassociated bacteria. The bacterial communities within the mesohyl of HMA sponges showed a close relationship to each other and seem to be sponge-specific.