4 Material und Umwelt
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Organisationseinheit der BAM
- 4.1 Biologische Materialschädigung und Referenzorganismen (55) (entfernen)
Eingeladener Vortrag
- nein (15)
This application note presents how EnviroESCA can be used to analyze bacterial samples under near ambient pressure conditions in various states of hydration using different levels of humidity. Such investigations of bacterial cell wall surfaces in their hydrated state are essential for studying biological interfaces at work.
The use of innovative near-ambient pressure (NAP-)XPS instrumentation allows the detailed analysis of irregularly-surfaced biofilms. NAP-XPS enables the surface analysis of bacterial samples in their natural hydrated state without complex sample preparation techniques such as freeze-drying or fast-freezing, which are needed for XPS analysis in ultrahigh vacuum.
ABSTRACT: A collection of thioimidazolium salts were synthesized and used as a new class of nonvolatile alkylating agents. Their nonvolatility prevents exposure during use or handling and are thus drastically safer than conventional alkylating agents. We discovered that thioimidazolium Iodide salts cannot release volatile compounds in the solid state, but instead only decompose when molten. Since decomposition proceeds via alkyl iodide elimination, SN2 of iodide on the thioimidazolium cation is constrained in the solid state, and instead can occur only upon melting when ions are mobile. By smart design of these alkylators, the melting point and thus the decomposition temperature of these salts can be increased from 106 to 169 °C and release negligible volatile organic compounds prior to melting. Thioimidazolium-bis(trifluoromethanesulfonyl)imide (TFSI) ionic liquids act as a completely nonvolatile and air-stable TFSI-based alkylating agent and can be used for high-throughput Synthesis of TFSI ionic liquids without solvent. Alkyl groups from methyl to dodecyl can be transferred to a nucleophile and the product purified by sublimation of the thione byproduct, which can then be recycled. We also found that thioimidazolium salts with a dodecyl chain are bactericidal, yet can hydrolyze in water to form benign neutral products, and thus wont accumulate in the environment. These results demonstrate that thioimidazolium salts are a designable platform for the pursuit of safer and more environmentally friendly alkylating and antiseptic agents.
Microbiologically influenced corrosion (MIC) is an expensive but unpredictable problem for the industries. The most well-known culprit for MIC is the sulfate-reducing microorganisms (SRM), such as members from the genus Desulfovibrio. It has been widely accepted that SRM can contribute significantly to MIC through the production of hydrogen sulfide (HS-) or in some cases a direct electron uptake from the metal surface. However, in a real environmental system, SRM is not exclusive and often involved with other microorganisms that may also contribute to MIC, such as methanogens.
Methanogenic archaea can produce methane (CH4) using H2+CO2, formate, methylated amines or acetate. Methanogens are highly abundant in the environment and many are found in very extreme conditions, such as high temperature and high salinity. Previous researches have demonstrated that methanogens are capable of MIC, though the specific mechanisms are still under investigation. In the oil and gas industry, methanogens are not considered as the main contributor for MIC since the corrosion rates are often too low. However, the tests for methanogen-induced MIC are usually performed at static conditions, which cannot represent the system accurately. Here, we developed a novel anaerobic system to evaluate the corrosion potential of methanogens under flow conditions. We will use the Methanococcus maripaludis KA1 strain, which was isolated from a crude oil tank, as the organism of interest. A separate system for Desulfovibrio alaskensis will be established for corrosion rate comparisons. Furthermore, we will study the synergistic effects of M. maripaludis and D. alaskensis on MIC under flow.
The evolutionary success of termites has been driven largely by a complex communication system operated by a rich set of exocrine glands. As many as 20 different exocrine organs are known in termites. While some of these organs are relatively well known, only anecdotal observations exist for others. One of the exocrine organs that has received negligible attention so far is the labral gland. In this study, we examined the structure and ultrastructure of the Labrum in soldiers of 28 termite species. We confirm that the labral gland is present in all termite species, and comprises two secretory regions located on the ventral side of the labrum and the dorso-apical part of the hypopharynx. The Labrum of Neoisoptera has a hyaline tip, which was secondarily lost in Nasutitermitinae, Microcerotermes and species with snapping soldiers. The epithelium of the gland generally consists of class 1 secretory cells, with an addition of class 3 secretory cells in some species. A common feature of the secretory cells is the abundance of smooth endoplasmic reticulum, an organelle known to produce lipidic and often volatile secretions. Our observations suggest that the labral gland is involved in communication rather than defence as previously suggested. Our study is the first to provide a comprehensive picture of the structure of the labral gland in soldiers across all Termite taxa.
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 importance of soldiers to termite Society defence has long been recognized, but the contribution of soldiers to other societal functions, such as colony immunity, is less well understood.
We explore this issue by examining the role of soldiers in protecting nestmates against pathogen infection. Even though they are unable to engage in grooming behaviour, we find that the presence of soldiers of the Darwin termite, Mastotermes darwiniensis, significantly improves the survival of nestmates following entomopathogenic infection.
We also show that the copious exocrine oral secretions produced by Darwin termite soldiers contain a high concentration of Proteins involved in digestion, chemical biosynthesis, and immunity. The oral secretions produced by soldiers are sufficient to protect nestmates against infection, and they have potent inhibitory activity against a broad spectrum of microbes. Our findings support the view that soldiers may play an important role in colony immunity, and broaden our understanding of the possible function of soldiers during the origin of soldier-first societies.
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.
Surface characterisation of Escherichia coli under various conditions by near-ambient pressure XPS
(2018)
Bacteria are inherently in a hydrated state and therefore not compatible to ultra-high vacuum techniques such as XPS without prior sample preparation involving freeze drying or fast freezing.
This has changed with the development of near-ambient pressure (NAP)-XPS, which makes it possible to characterise the bacterial surface with minimal sample preparation. This paper presents NAP-XPS measurements of Escherichia coli under various NAP conditions: at 11 mbar in a humid environment, at 2 mbar after drying in the chamber, pre-dried at 4 mbar, and at 1 mbar after overnight pumping at 10^−4 mbar. The high-resolution spectra of carbon, nitrogen, and oxygen are presented and found to be in general agreement with XPS measurements from freeze-dried and fast-frozen bacteria. However, it was found that the amount of carbon components associated with polysaccharides increases relative to aliphatic carbon during drying and increases further after overnight pumping. This implies that drying has an impact on the bacterial surface.
A presentation held for the seminar "Ausgewählte analytische Methoden der Physik" hosted by Prof. Birgit Kanngießer at TU Berlin. The first part focus on depth-dependent XPS-measurements (XPS, synchrotron HAXPES) to obtain a concentration profile of iodine in an artificial biofilm. In the second part, NAP-XPS measurements of various bacterial samples are presented.
Surface characterisation of biofilms by nearambient pressure X-ray photoelectron spectroscopy
(2018)
The XPS information depth of approximately 10 nm is in the same size range as the outer membrane of the gram-negative bacteria, which makes XPS a suitable tool for determining the elemental composition of the bacterial surface and monitor changes caused by outer stress like dehydration or exposure to antimicrobials. However, bacteria are inherently in a hydrated state, and therefore only compatible to ultra-high vacuum after extensive sample preparation, which may degrade the sample constituents. This issue is addressed by the development of near-ambient pressure (NAP)-XPS, which enables bacteria and biofilms to be characterised in their native wet state. Artificial biofilms, bacteria and biofilms of Escherichia coli have been characterised with the laboratory NAP-XPS instrument EnviroESCA from SPECS GmbH, at pressures ranging from high vacuum to 12 mbar, and in both humid and dry environment. By studying biological samples in their native wet state, new insight about composition and transport of drugs through cell membranes and the extracellular polymeric substance (EPS) of biofilms can be obtained.