4 Material und Umwelt
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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.
Biofilm formation on materials leads to high costs in industrial processes, as well as in medical applications. This fact has stimulated interest in the development of new materials with improved surfaces to reduce bacterial adhesion.
We present a flow chamber system to test and quantify bacterial adhesion on materials that are part of antifouling concepts. The adhesion process is standardized and can be adapted to different bacteria in subaquatic of subaerial environments. It is combined with a standardized evaluation procedure based on statistical evidence.
Soil microbes are exposed to different environmental stressors originating from various sources. Biocides used as material preservatives can represent environmental stressors since they are in direct contact with the environment including soil. Microorganism in soils can adapt to stress by different mechanisms; for example, by the evolution of resistance by de novo mutations or acquisition of resistance genes via horizontal gene transfer (HGT). Here, we hypothesize that material preservatives could enhance the evolution of biocide resistance enabling the potential for cross-resistance to antibiotics. Furthermore, we hypothesize that material preservatives can cause increased frequencies of HGT (i.e. altered community permissiveness) facilitating microbial community adaptation to stress. We will culture soil microorganism with increasing concentrations of selected biocides followed by antibiotic susceptibility determination. Moreover, we will incubate soil mesocosms with selected biocides to investigate if these compounds promote HGT of plasmids that carry resistance genes in soil microbial communities. Together these results will elucidate the potential for the evolution of biocide resistance and cross-resistance to antibiotics as well as the effect of biocides on adaptation to environmental stressors in soil microbial communities.
Soil microbes are exposed to different environmental stressors originating from various sources. Biocides used as material preservatives can represent environmental stressors since they are in direct contact with the environment including soil. Microorganism in soils can adapt to stress by different mechanisms; for example, by transferring mobile genetic elements via horizontal gene transfer (HGT). Here, we hypothesize that material preservatives can cause increased frequencies of HGT (i.e. altered community permissiveness) facilitating microbial community adaptation to stress. Furthermore, we hypothesize that soil microbial communities are primed by biocide exposure facilitating the response to different types of stresses. We will incubate soil mesocosms with selected biocides to investigate if these compounds promote HGT of plasmids that carry resistance genes in soil microbial communities. Subsequently, we will prime the soil microbial community with sub-inhibitory concentrations of biocides followed by exposure to toxic biocide concentrations or other types of common environmental stresses including metals, antibiotics, and salt. Using suitable control experiments, a shift in the functional response of the primed as compared to the non-primed community would indicate that biocides prime microbial communities via HGT. Together these results will elucidate the effect of biocides on HGT-mediated adaptation to environmental stressors in soil microbial communities.
Soil microbes are exposed to different environmental stressors originating from various sources. Biocides used as material preservatives can represent environmental stressors since they are in direct contact with the environment including soil. Microorganism in soils can adapt to stress by different mechanisms; for example, by transferring mobile genetic elements via horizontal gene transfer (HGT). Here, we hypothesize that material preservatives can cause increased frequencies of HGT (i.e. altered community permissiveness) facilitating microbial community adaptation to stress. Furthermore, we hypothesize that soil microbial communities are primed by biocide exposure facilitating the response to different types of stresses. We will incubate soil mesocosms with selected biocides to investigate if these compounds promote HGT of plasmids that carry resistance genes in soil microbial communities. Subsequently, we will prime the soil microbial community with sub-inhibitory concentrations of biocides followed by exposure to toxic biocide concentrations or other types of common environmental stresses including metals, antibiotics, and salt. Using suitable control experiments, a shift in the functional response of the primed as compared to the non-primed community would indicate that biocides prime microbial communities via HGT. Together these results will elucidate the effect of biocides on HGT-mediated adaptation to environmental stressors in soil microbial communities.
The halophilic bacterium Halomonas elongata can tolerate salt concentrations above 10% NaCl and uses the accumulation of the compatible solute ectoine as a major osmoregulatory mechanism. Ectoine can be accumalted inside the cell through import from the medium or de novo synthesis and establishes an osmotic equilibrium with the surrounding1. Ectoine also protects proteins from the effects of freezing, drying and high temperatures4 and DNA from ionizing radiation2. These features make ectoine a valuable compound for cosmetics and medical devices.
H. elongata was originally isolated from a solar salt facility, where it thrives under high salt concentrations. It was found that marine prokaryotes, which are exposed to high oxidative stress in their environment, vary glycolytic strategies5. A variation in the use of the glucose metabolic pathways is also assumed for H. elongata.
The halophilic bacterium Halomonas elongata can tolerate salt concentrations above 10% NaCl and uses the accumulation of the compatible solute ectoine as a major osmoregulatory mechanism. Ectoine can be accumalted inside the cell through import from the medium or de novo synthesis and establishes an osmotic equilibrium with the surrounding1. Ectoine also protects proteins from the effects of freezing, drying and high temperatures4 and DNA from ionizing radiation2. These features make ectoine a valuable compound for cosmetics and medical devices.
H. elongata was originally isolated from a solar salt facility, where it thrives under high salt concentrations. It was found that marine prokaryotes, which are exposed to high oxidative stress in their environment, vary glycolytic strategies5. A variation in the use of the glucose metabolic pathways is also assumed for H. elongata.
The Cairo Geniza is an “archive” discovered in the 19th century in Ben Ezra Synagogue in Fustat, a district in Old Cairo (Egypt), located south of the center of modern Cairo. The giant collection of mostly Jewish documents that vary in genres, languages and writing supports contains a large number of early medieval Hebrew manuscripts, mostly in fragmentary form. The larger part of the Cairo Geniza is stored today in the Cambridge University Library (CUL).
The Geniza provides sources for the literary, linguistic, historical studies of the various aspects Jewish life. As the documents attest, at least two Jewish communities co-existed in Fustat up to 11th century: a so-called Babylonian and Palestinian. These communities had different leaders, different traditions and lived independently. The differences seem to manifest themselves also in the paleographical, codicological and some material properties of the manuscripts produced by each community.
The aim of this project is to compare the inks used in the Jewish documents depending on different variables: support (paper, parchment), purpose of the manuscript (legal, private, religious), provenance of the scribe. For the determination of the inks type and composition we had to choose non-invasive, non-destructive and portable techniques to analyse the corpus directly in the CUL.
The analyses were carried out with a mobile energy dispersive micro-X-ray spectrometer ArtTAX® (Bruker GmbH, Berlin, Germany), which consists of an air-cooled, low-power molybdenum tube, polycapillary X-ray optics (measuring spot size 70 µm in diameter), an electrothermally cooled Xflash detector, and a CCD camera for sample positioning (Bronk et al 2001, Hahn et al. 2010). All measurements are executed using a 30 W low-power Mo tube, 50 kV, 600 µA Mo tube, and with an acquisition time of 15 s (live time) to minimize the risk of damage (Fig. 1, 2).
Fig. 1: XRF spectrometer probe above a manuscript fragment
Fig. 2: Typical element profile of a XRF linescan
The Dino Lite digital stereomicroscope (Fig. 3) features built-in LED illumination at 395 nm and 940 nm and a customized external white light source. During use, the microscope is fastened to a small tripod or mounted on a Plexiglas ring holder that incorporates a white light source.
Fig. 3: Dino Lite digital stereomicroscope
Fig. 4: Details of one fragment (T-S 16.124) observed with the Dino microscope (x20). On the left, when illuminated with NIR (Near-Infrared, 940 nm) light, the ink fades, indicating iron-gall ink. On the right, the image under NIR light does not change. It is carbon ink.
On example of these studies is the manuscript T-S 16.124 (Cambridge University Library, Fig. 5) whom belongs to the third corpus. It is a deed, written in Hebrew, dated from 1328 (= 1017 CE) and witnessed by a very high number of people (6) comparing to the standard of similar documents (between 2 and 3), from at least two different Jewish communities in Fustat (trans congregational). The verso is written in Arabic (Bareket 1999).
Fig. 5: Manuscript T-S 16.124 (Cambridge University Library)
To compare the inks, we used the fingerprint model. This method relies on the determination of characteristic elemental compositions and represents the amount of a minor constituent relative to the main component, iron in iron gall ink (Malzer et al. 2004, Hahn et al. 2004, Rabin et al 2014). However, a calculation of a fingerprint based on XRF measurements is not possible in the case of carbon ink since carbon, its main component, cannot be detected with this technique.
Fig. 6: Ink fingerprint T-S 16-124 (recto) normalized to iron (Fe)
Conclusion
We show that using reflectography and XRF analysis it is possible to sort the inks according to their type. In the case of the iron-gall inks, use of the ink fingerprint, i.e. amount of the vitriol components normalized to iron we can make direct comparisons of the ink composition.
We would like also to stress that though the methods of material analysis listed above have been successfully employed in the field of cultural heritage and conservation including ancient and medieval manuscripts they have not yet been used to study fragments from the Cairo Genizah. Therefore, we believe that this research project is a pioneering study that will provide new insights into the history of Hebrew writing materials, their production techniques and materials and, thus, contribute new data to the field of Hebrew paleography.
While studying the socio-geographic history of inks, division 4.5 of the BAM (Bundesanstalt für Materialforschung und Prüfung) together with the Centre for the Study of Manuscript Cultures in Hamburg has developed a protocol for ink analysis. It consists of a primary screening to determine the type of the ink and a subsequent in-depth analysis using several spectroscopic techniques: XRF, FTIR, and Raman. In most cases, we can obtain satisfactory results using a non-invasive protocol. However, mixed inks that contain no metals evade such a protocol. These inks constitute a heterogeneous group of media used especially in the Middle East and the Islamicate world since at least the 10th century; they are characterized by blending carbon ink and tannins, with or without the addition of vitriol.
Our own research aims primarily at recreating a socio-geographic history of inks, parchment, and papyrus and includes the comparative analysis of the writing materials of the Dead Sea Scrolls, ink and papyrus in Ancient and Hellenistic Egypt, and inks in documents from various contemporary medieval communities in Fustat (first nucleus of Cairo). During many years of study, we concluded that the continuous production of Coptic manuscripts from late Antiquity to the Middle Ages offers a unique opportunity for historical study of the ink in a large geographic area. Thanks to the collaboration with the ERC project “PAThs” (www.paths.uniroma1.it), based at the University of Rome La Sapienza, and within the activities of a PhD research dedicated to this topic, we therefore created a new branch of our project focused entirely on the analysis of Coptic inks, pigments, and dyes. This pioneering systematic study of writing materials coming from a specific area and time frame (5th-10th century) aims not only at a better understanding of the complex Coptic multicultural and plurilingual society, but also and mainly at clarifying the links among the Coptic and other societies between the ancient and medieval eras. Finally, it will cast light on the history of the technological development of inks in the eastern world, from Antiquity to the middle ages.
Microbiologically influenced corrosion (MIC) is the deterioration of metals due to the metabolic activities of microorganisms. Microorganisms can take electrons directly from the metal surface (EMIC) thereby causing corrosion. Well known culprits of EMIC are: sulfate-reducing bacteria (SRB), acetogens and methanogens.
Our aims
- Develop a novel flow system to study MIC by methanogens to mimic industrial Environments
- Investigate the inhibitory concentrations of biocides targeting SRB on corrosive methanogenic strains
- Investigate the inhibitory effects of corrosion inhibitors on methanogens
- Compare the inhibitory concentrations to SRB
A wide range of methods are used to estimate the plant-availability of soil phosphorus (P). Published research has shown that the diffusive gradients in thin films (DGT) technique has a superior correlation to plant-available P in soils compared to standard chemical extraction tests. In order to identify the plant-available soil P species, we combined DGT with infrared and P K- and L-edge X-ray adsorption near-edge structure (XANES) spectroscopy. This was achieved by spectroscopically investigating the dried binding layer of DGT devices after soil deployment. All three spectroscopic methods were able to distinguish between different kinds of phosphates (poly-, trimeta-, pyro- and orthophosphate) on the DGT binding layer. However, infrared spectroscopy was most sensitive to distinguish between different types of adsorbed inorganic and organic phosphates. Additionally, also intermediates of the time-resolved hydrolysis of trimetaphosphate in soil could be analyzed. Furthermore, infrared and XANES microspectroscopy make it also possible to analyze P compounds on the binding layer with a lateral resolution down to 1 µm2. Therefore, P species of a spatial soil segment (e.g. rhizosphere) can be mapped and analyzed.
In Vorbereitung einer Restaurierung erfolgten naturwissenschaftliche Untersuchungen zu Schadensphänomenen und Glaszusammensetzungen an mittelalterlichen Gläsern aus der Dorfkirche in Koszewko (Polen)im Environmental Scanning Electron Microscope (ESEM) mit EDX. Die Ergebnisse zeigen, dass die Glasverwitterung schon sehr stark vorangeschritten ist und ein zukünftiger Schutz der mittelalterlichen Glasmalereifelder vor Umwelteinflüssen unbedingt notwendig ist. Es wurde ein Schutzverglasungsystem entwickelt, das speziell auf den langfristigen Erhalt der einzelnen mittelalterlichen Glasmalereifelder ausgelegt ist.
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.
We demonstrate a 2D platform based on high contrast wetting patterns suitable for miniaturized microbiological assays.
In principal, superhydrophilic spots are surrounded by a superhydrophobic surface area. The special structure of the superhydrophilic functional surface ensures that liquids, e.g. bacterial suspensions or biocide solutions, spread immediately and evenly on this surface without passing the wetting boundary. This feature allows a homogenous distribution of bacteria or chemical substances on well defined lateral dimensions. The superhydrophilic spots may also serve as substrate for bacterial biofilms. Due to the high wetting contrast and the fabrication process, it is possible to minimize the test areas as well as their distance to each other.
We demonstrate the fabrication process of the high wetting contrast platform and also present a microbiological assay as an application example. Advantages of this platform are the use of low volumes and its potential of automated analysis.
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.
Microbiologically influenced corrosion (MIC) is the deterioration of metals due to the metabolic activities of microorganisms. Microorganisms can take electrons directly from the metal surface (EMIC) thereby causing corrosion. Well known culprits of EMIC are: sulfate-reducing bacteria (SRB), acetogens and methanogens.
There is a need for an assessment of the emission properties of volatile organic compounds (VOCs) from consumer products. A method comparison was carried out to evaluate adapted and cost-effective procedures for such items. Smaller and automated emission chambers de-picted similar kinetics compared to a 203 L standard chamber. Toy samples made of PVC (Polyvinyl chloride) emitted more VOCs compared to other tested polymeric products. The emissions from 2 selected samples were studied to allow an evaluation of the resulting room concentration and external exposure of a child. Obtained concentrations were not of concern.
Comparison of Formaldehyde Concentrations in Emission Test Chambers Using EN 717-1 and EN 16516
(2018)
For many years EN 717-1 (Wood-based panels - Determination of formaldehyde release - Part 1: Formaldehyde emission by the chamber method) is the standard for formaldehyde emission testing of wooden boards. In 2017 EN 16516 (Construction products - Assessment of release of dangerous substances - Determination of emissions into indoor air) was published as a new harmonised standard for the emission testing of construction products. Because test chamber conditions are different, both standards give different concentrations for formaldehyde. For the determination of a conversion factor four test series were set up with different wooden boards.
Sintered bioactive glass scaffolds of defined shape and porosity, e.g. made via additive manufacturing, must provide sufficient bioactivity and sinterability. As higher bioactivity is often linked to high corrosion and crystallization tendency, a certain compromise between sintering ability and bioactivity is therefore required. Groh et al. developed a fluoride-containing bioactive glass (F3), which allows fiber drawing and shows a bioactivity well comparable to that of Bioglass®45S5.
To study whether and to what extent the sinterability of F3 glass powder is controlled by particle size, coarse and fine F3 glass powders (300-310µm and 0-32µm) were prepared by crushing, sieving and milling. Sintering, degassing and phase transformation during heating were studied with heating microscopy, vacuum hot extraction (VHE), DTA, XRD, and SEM.
For the coarse glass powder, sintering proceeds slowly and is limited by surface crystallization of primary Na2CaSi2O6 crystals. Although the crystallization onset of Na2CaSi2O6 is shifted to lower temperature, full densification is attained for the fine powder. This finding indicate that certain porosity might be tuned via particle size variation. Above 900°C, intensive foaming is evident for the fine powder. VHE studies revealed that carbon species are the main foaming source.