4.1 Biologische Materialschädigung und Referenzorganismen
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ICP-ToF (time of flight) MS enables the analysis of the multi-element fingerprint of single cells. The single cell ICP-ToF-MS is used in the presented poster for the analysis of archaea involved in microbiologically influenced corrosion (MIC) of steel. By means of sc-ICP-ToF-MS, the possible uptake of individual elements from the respective steel is investigated - the information obtained will be used in the future to elucidate underlying mechanisms and develop possible material protection concepts. The work combines modern methods of analytical sciences with materials.
The latest ICP-MS technology - ICP-ToF (time of flight)-MS – enables the analysis of the multi-element fingerprint of individual cells. The interface between material and environmental analysis thus receives special attention, e.g., when considering corrosion processes. Microbiologically influenced corrosion (MIC) is a highly unpredictable phenomenon due to the influence of the environment, microbial communities involved and the respective electron source. However, the interaction pathway between cells and the metal surface remains unclear. The development of the MIC-specific ICP-ToF-MS analytical method presented here at the single cell level, in combination with the investigation of steel-MIC interactions, contributes significantly to progress in instrumental MIC analysis and will enable clarification of the processes taking place. For this, a MIC-specific staining procedure was developed. It allows the analysis of archaea at a single cell level and provides information about the interaction of the cells with the staining agent which is extremely scarce compared to other well characterized organisms. Additionally, the single cell ICP-ToF-MS is used for the analysis of archaea involved in MIC of steel. Hence, the possible uptake of individual elements from different steel samples is investigated - the information obtained will be used in the future to elucidate underlying mechanisms and develop possible material protection concepts, thus combining modern methods of analytical sciences with materials.
In recent years, the fabrication of laser-generated surface structures on metals such as titanium surfaces have gained remarkable interests, being technologically relevant for applications in optics, medicine, fluid transport, tribology, and wetting of surfaces.
The morphology of these structures, and so their chemistry, is influenced by the different laser processing parameters such as the laser fluence, wavelength, pulse repetition rate, laser light polarization type and direction, angle of incidence, and the effective number of laser pulses per beam spot area.
However, the characterization of the different surface structures can be difficult because of constraints regarding the analytical information from both depth and the topographic artifacts which may limit the lateral and depth resolution of elemental distributions as well as their proper quantification. A promising technique to investigate these structures even at the nano-scale is Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), a very surface sensitive technique that at the same time allows to perform depth-profiling, imaging and 3D-reconstruction of selected ion-sputter fragment distributions on the surface.
In this study we combine chemical analyses such as Energy Dispersive X-ray spectroscopy (EDX) and high-resolution scanning electron microscopy (SEM) analyses with ToF-SIMS to fully characterize the evolution of various types of laser-generated micro- and nanostructures formed on Ti and Ti alloys at different laser fluence levels, effective number of pulses and at different pulse repetition rates (1 – 400 kHz), following irradiation by near-infrared ultrashort laser pulses (925 fs, 1030 nm) in air environment or under argon gas flow.
We show how this combined surface analytical approach allows to evaluate alteration in the surface chemistry of the laser-generated surface structures depending on the laser processing parameters and the ambient environment.
Biofilm formation in industrial or medical settings is usually unwanted and leads to serious health problems and high costs. Inhibition of initial bacterial adhesion prevents biofilm formation and is, therefore, a major mechanism of antimicrobial action of surfaces. Surface topography largely influences the interaction between bacteria and surfaces which makes topography an ideal base for antifouling strategies and eco-friendly alternatives to chemical surface modifications. Femtosecond laser-processing was used to fabricate sub-micrometric surface structures on silicon and stainless steel for the development of antifouling topographies on technical materials.
Up to now, different analytical methods for single cell analysis exist focusing on key features such as size, shape, morphology and elemental composition. The combination of the latest ICP-MS techniques - ICP-ToF-MS - together with the latest developments in the field of sample delivery - micro droplet generator (MDG) – will allow a Deep insight into the composition and size of cells.
Microbiologically influenced corrosion (MIC) is an oxidation of metals affected by the presence or activity (or both) of microorganisms e.g. Shewanella Putrefaciens in biofilms on the surface of the corroding material. As this can happen for example in the soil on iron pipes of water pipes, in oil tanks or on steel sheet piling, there is great interest in MIC research, not only from various industrial sectors, but also from the environmental aspect.
Biocide mitigation strategies of microbiologically influenced corrosion (MIC) in the oil and gas industry have been primarily used to eliminate the growths of sulfate-reducing microorganisms (SRM). However, methanogenic Archaea (MA) can also be highly corrosive by using iron as an electron source for methanogenesis. Because of the fundamental physiological differences between archaea and bacteria, responses of MA towards SRM-specific biocides cannot be deduced using SRM. Due to the lack of information available on the effect of biocides on corrosive MA, we selected THPS, glutaraldehyde, nitrate and perchlorate to compare against corrosive SRM.
Preliminary results showed that at low concentrations of THPS (0-10 ppm), growth of MA was not affected, methane production and corrosion rates (0.1 mm/yr) were comparable between the different THPS concentrations. On the contrary, the SRM strain showed decreased corrosion rates (0.18 mm/yr to 0.03 mm/yr) with increasing THPS concentrations. Further corrosion tests including electrochemical measurements of different biocides on the growth of MA and SRM will be conducted. Such knowledge not only provide important insights on the physiological response of MA to biocides but also contribute to more effective mitigation strategies that can be both economic and environmentally beneficial.
Microbiologically induced corrosion due to bacterial biofilms causes several problems in industrial systems, technical applications and in medicine. Prior to the formation of a biofilm on a substrate, planktonic cells attach on the surface. Hence, the properties of the surface play a key role in biofilm formation and are of great importance for the development of strategies to prevent bacterial attachment and biofilm formation.
This project aims at clarifying to which extent surface micro-/nanostructuring and chemical functionalization affects bacterial attachment and whether a synergistic combination of the two can be used to control bacterial adhesion. To answer these questions, model surfaces with regular patterns of 5-10 micrometers in size have been prepared, which provide distinct zones differing in terms of their chemistry or nano-roughness. This was achieved by micro contact printing of self-assembled monolayers with different functional groups and deposition of patterned ZnO nanorod arrays for studying the effect of surface chemistry and morphology, respectively. Typical contrasts studied were combinations of positively/negatively charged, hydrophobic/hydrophilic or flat/rough.
The attachment behavior of bacteria on tailored surfaces were studied in a flow chamber as a function of time. The strain Pseudomonas fluorescens SBW25 was chosen as a model organism. DNA-intercalating dyes such as Syto9 have a high affinity to adsorb on ZnO nanorods. To overcome this limitation a genetic modification was performed by introducing a gene which expresses a green fluorescent protein in P. fluorescens SBW25 enabling the quantitative evaluation of the flow chamber studies by means of fluorescence microscopy. Further analysis of the attachment behavior was performed by means of scanning electron microscopy.
The presentation will summarize the results of our systematic study on the role of individual parameters on bacterial attachment and highlight synergistic combinations, showing an inhibition or enhancing effect. As the investigations with model substrates enable a precise control of the surface parameters, this approach can be applied to different microorganisms and material systems to achieve a correlative description of bacterial adhesion on solid surfaces.
Since the early 19th century microorganisms were studied on their capabilities of causing microbiologically influenced corrosion (MIC) of metals. The most studied ones are sulfate-reducing bacteria (SRB), but others can corrode metals as well, e.g. acid-producing bacteria or methanogenic archaea (MA). However, these studies were mostly focused on metals related to the petroleum industry but metals for other industries, e.g. dentistry, are also susceptible to corrosion. The inert Titanium (Ti) is often used as an implant material, but it is a base metal. The formation of a passivating oxide layer allows Ti to be corrosion resistant at normal conditions.
Nonetheless, scanning electron microscope images on dental implants from patients with acute peri-implantitis showed clear signs of corrosion. Currently, the corrosion mechanism of dental implants is unknown, but many indications suggest that oral microorganisms, including MA (Methanobrevibacter oralis) and SRB (Desulfomicrobium orale), could be involved.
To determine if MA or SRB can corrode Ti (pure Ti or Ti-6Al-4V alloy), corrosion rate, methane and sulfide concentrations were analyzed. Electrical potential measurements using in-house developed electrochemical cells indicated a potential change on Ti in the presence of a corrosive MA strain compared to an abiotic control.
Microbial composition comparison will be analyzed using samples from dental pockets of 150 infected patients by considering the quality of the implant and 50 healthy people by means of amplicon sequencing. Enrichments and isolation of pure cultures from the dentals samples are also examined for their corrosion behavior. Overall, this is the first study investigating the susceptibility of dental implant material to corrosion using human related MA.
Microbially influenced corrosion (MIC) of iron is usually attributed to sulfate-reducing microorganisms (SRM) which act upon the metal by the reactiveness of hydrogen sulfide, and by withdrawal of the available electrons (Fe → Fe²⁺ + 2e⁻ ; E° = 0.47 V) in electrical contact through surface attachment. Also methanogenic archaea are supposed to cause MIC. Because they do not produce hydrogen sulfide, withdrawal of electrons may be their main corrosive mechanism; however, mechanistic details and kinetics of the overall process are poorly understood. Precipitation of siderite (4Fe + 5HCO₃⁻ + 5H⁺ → 4FeCO₃ + CH₄ + 3H₂O) can lead to an insulating layer on the metal surface and lower the corrosion rate. Still, the extent of FeCO₃ precipitation may be significantly influenced by environmental conditions such as pH and advective processes.
To investigate the corrosive potential of methanogens, we studied strains isolated from marine sediments (Methanococcus maripaludis 14266, 2067, Methanobacterium-affiliated strain IM1), crude oil tanks (Methanococcus maripaludis Mic1c10, KA1) and the oral cavity (Methanobrevibacter oralis) in a closed (batch) culture, and in a sand-packed flow-through cell with pH control and simulation of a fluctuating environment. Results indicate that the rates of iron corrosion due to coupled methanogenesis (up to 0.3 mm/yr) are comparable to that caused by SRM. Surface analyses of the metal showed severe pitting. Such knowledge and deeper understanding also from an electrokinetic point of view may not only provide further models in microbial electrophysiology, but also contribute to mitigation strategies in MIC.
Microbially influenced corrosion (MIC) of iron is usually attributed to sulfate-reducing microorganisms (SRM) which act upon the metal by the reactiveness of hydrogen sulfide, and by withdrawal of the available electrons in electrical contact with the metal. Methanogenic archaea can also cause MIC by directly withdrawing electrons from the iron surface for methanogenesis. However, the mechanistic details and kinetics of the overall process are poorly understood. Precipitation of siderite, a by-product of methanogenesis, (4Fe + 5HCO3 + 5H+ 4FeCO3 + CH4 + 3H2O) can lead to an insulating layer on the metal surface and lower the corrosion rate. Still, the extent of FeCO3 precipitation may be significantly influenced by environmental conditions such as pH and advective processes.
Microbiologically influence corrosion (MIC) has become a big concern due the increased usage of different metals by our society. Microorganisms can use metal as an electron donor, causing unpredictable but serious damages. Nowadays it is known that besides sulfate reducing bacteria (SRB), other microorganisms including acetogens, iron oxidizers and methanogens can also induce MIC. Current studies related to methanogen-induced MIC (MI-MIC) mainly focused on environmental isolates from the oil and gas industry (e.g. Methanococcus maripaludis) with industrial materials e.g. iron. However, MI-MIC can occur in many other environments as well, including the oral cavity. Methanobrevibacter oralis is a methanogen isolated from the human oral cavity and was found more frequently in patients suffering from peri-implantitis/periodontitis. Titanium-implants removed from those patients have also showed clear signs of corrosion. The aim of our study is to establish and analyze corrosion potentials of dental metals (e.g. titanium) by oral methanogens. Periodontal pockets samples from patients suffering from periodontitis/peri-implantitis were taken for methanogenic and SRB enrichments. Stainless steel, pure titanium or Ti-6Al-4V alloy was used for corrosion studies. Corrosion rates and methane production were measured using weight-loss method and gas chromatography, respectively. Metal surfaces were visualized with scanning electron microscopy. Microbial communities in the dental pockets of healthy people and patients will be compared using 16S rRNA amplicon sequencing. Overall, this is the first study investigating the susceptibility of different dental implant materials to corrosion using human-related Archaea. The outcomes of this study can be further explored for a variety of clinical applications.
The characteristics of different molecules chosen as representatives for specific functionalities in conditioning layers play an important role on attachment behavior and later biofilm formation of bacteria. The chemical composition is a major component influencing the attachment but there is a conglomerate of influences.
Microbially influenced corrosion (MIC) of iron is usually attributed to sulfate-reducing microorganisms (SRM) which act upon the metal by the reactiveness of hydrogen sulfide, and by withdrawal of the available electrons in electrical contact with the metal. Methanogenic archaea are supposed to cause MIC. Because they do not produce hydrogen sulfide, withdrawal of electrons may be their main corrosive mechanism; however, mechanistic details and kinetics of the overall process are poorly understood. Precipitation of siderite (4Fe + 5HCO3 + 5H+ 4FeCO3 + CH4 + 3H2O) can lead to an insulating layer on the metal surface and lower the corrosion rate. Still, the extent of FeCO3 precipitation may be significantly influenced by environmental conditions such as pH and advective processes.
Microbially influenced corrosion (MIC) of iron is usually attributed to sulfate-reducing microorganisms (SRM) which act upon the metal by the reactiveness of hydrogen sulfide, and by withdrawal of the available electrons in electrical contact with the metal. Methanogenic archaea are supposed to cause MIC. Because they do not produce hydrogen sulfide, withdrawal of electrons may be their main corrosive mechanism; however, mechanistic details and kinetics of the overall process are poorly understood. Precipitation of siderite (4Fe + 5HCO3 + 5H+ 4FeCO3 + CH4 + 3H2O) can lead to an insulating layer on the metal surface and lower the corrosion rate. Still, the extent of FeCO3 precipitation may be significantly influenced by environmental conditions such as pH and advective processes.