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- 4 Material und Umwelt (270)
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Paper des Monats
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Many microorganisms including free-living and symbiotic fungi weather minerals through the formation of biofilms on their surface. Weathering thus proceeds not only according to the mineral’s chemistry and the environmental conditions but also according to the local biofilm chemistry. These processes can be dissected in experiments with defined environmental settings and by employing genetic tools to modify traits of the fungal biofilm. Biofilms of the rock-inhabiting fungus Knufia petricola strain A95 (wild-type, WT) and its melanin-deficient mutant (ΔKppks) were grown on polished olivine sections in subaerial (air-exposed) and subaquatic (submerged) conditions. After seven months of interaction at pH 6 and 25°C, the fungus-mineral interface and abiotic olivine surface were compared using high resolution transmission electron microscopy (HRTEM). The abiotic, subaquatic olivine section showed a 25 nm thick, continuous amorphous layer, enriched in Fe and depleted in Si compared to the underlying crystalline olivine. This amorphous layer formed either through a coupled interfacial dissolution reprecipitation mechanism or through the adsorption of silicic acid on precipitated ferric hydroxides. Its thickness was likely enhanced by mechanical stresses of polishing. Directly underneath a fungal biofilm (WT and mutant alike), the surface remained mostly crystalline and was strongly etched and weathered, indicating enhanced olivine dissolution. The correlation between enhanced olivine dissolution and the absence of a continuous amorphous layer is a strong indication of the dissolution-inhibiting qualities of the latter. We propose that the fungal biofilm sequesters significant amounts of Fe, preventing formation of the amorphous layer and driving olivine dissolution onwards. The seemingly similar olivine surface underneath both WT and mutant biofilms illustrates the comparably insignificant role of specific biofilm traits in the weathering of olivine once biofilm attachment is imposed. Under subaerial conditions, the absence of water on the abiotic surface prohibited olivine dissolution. This was overcome by the water retention capacities of both the WT and mutant biofilm: the olivine surface underneath subaerial fungal biofilms was as weathered as the corresponding subaquatic olivine surface. Under the studied environmental settings, the effect of fungal biofilms on olivine weathering seems to be universal, independent of the production of melanin, the composition of extracellular polymeric substances (EPS) or air-exposure.
Over the past two decades, per- and polyfluoroalkyl substances (PFASs) have emerged as worldwide environmental contaminants, calling out for sophisticated treatment, decomposition and remediation strategies. In order to mineralize PFAS pollutants, the incineration of contaminated material is a state-of-the-art process, but more cost-effective and sustainable technologies are inevitable for the future. Within this review, various methods for the reductive defluorination of PFASs were inspected. In addition to this, the role of mechanochemistry is highlighted with regard to its major potential in reductive defluorination reactions and degradation of pollutants. In order to get a comprehensive understanding of the involved reactions, their mechanistic pathways are pointed out. Comparisons between existing PFAS decomposition reactions and reductive approaches are discussed in detail, regarding their applicability in possible remediation processes. This article provides a solid overview of the most recent research methods and offers guidelines for future research directions.
Salt tolerance in the γ-proteobacterium Halomonas elongata is linked to its ability to produce the compatible solute ectoine. The metabolism of ectoine production is of great interest since it can shed light on the biochemical basis of halotolerance as well as pave the way for the improvement of the biotechnological production of such compatible solute. Ectoine belongs to the biosynthetic family of aspartate-derived amino-acids. Aspartate is formed from oxaloacetate, thereby connecting ectoine production to the anaplerotic reactions that refill carbon into the tricarboxylic acid cycle (TCA cycle). This places a high demand on these reactions and creates the need to regulate them not only in response to growth but also in response to extracellular salt concentration. In this work, we combine modeling and experiments to analyze how these different needs shape the anaplerotic reactions in H. elongata. First, the stoichiometric and thermodynamic factors that condition the flux distributions are analyzed, then the optimal patterns of operation for oxaloacetate production are calculated. Finally, the phenotype of two deletion mutants lacking potentially relevant anaplerotic enzymes: phosphoenolpyruvate carboxylase (Ppc) and oxaloacetate decarboxylase (Oad) are experimentally characterized. The results show that the anaplerotic reactions in H. elongata are indeed subject to evolutionary pressures that differ from those faced by other gram-negative bacteria. Ectoine producing halophiles must meet a higher metabolic demand for oxaloacetate and the reliance of many marine bacteria on the Entner-Doudoroff pathway compromises the anaplerotic efficiency of Ppc, which is usually one of the main enzymes fulfilling this role. The anaplerotic flux in H. elongata is contributed not only by Ppc but also by Oad, an enzyme that has not yet been shown to play this role in vivo. Ppc is necessary for H. elongata to grow normally at low salt concentrations but it is not required to achieve near maximal growth rates as long as there is a steep sodium gradient. On the other hand, the lack of Oad presents serious difficulties to grow at high salt concentrations. This points to a shared role of these two enzymes in guaranteeing the supply of oxaloacetate for biosynthetic reactions.
Popioły pochodzące z instalacji do spalania komunalnych osadów ściekowych, znajdującej się na terytorium Polski, poddano procesom termochemicznego przekształcania, dzięki czemu otrzymano produkty nawozowe spełniające kryteria dopuszczające je do obrotu jako nawozy mineralne. Ponadto dokonano analizy możliwości wykorzystania popiołów na cele nawozowe zgodnie z obecnie przyjętymi dokumentami strategicznymi i planistycznymi dotyczącymi gospodarki odpadami na poziomie krajowym i europejskim.
The evolutionary success of insects is promoted by their association with beneficial microbes that enable the utilization of unusual diets. The synanthropic clothing moth Tineola bisselliella provides an intriguing example of this phenomenon. The caterpillars of this species have adapted to feed on keratin-rich diets such as feathers and wool, which cannot be digested by most other animals and are resistant to common digestive enzymes. Inspired by the hypothesis that this ability may be conferred by symbiotic microbes, we utilized a simple assay to detect keratinase activity and a method to screen gut bacteria for candidate enzymes, which were isolated from feather-fed larvae. The isolation of DNA from keratin-degrading bacterial strains followed by de novo genome sequencing resulted in the identification of a novel bacterial strain related to Bacillus sp. FDAARGOS_235. Genome Annotation identified 20 genes with keratinase domains. Proteomic analysis of the culture supernatant from this gut bacterium grown in non-nutrient buffer supplemented with feathers revealed several candidate enzymes potentially responsible for keratin degradation, including a thiol-disulfide oxidoreductase and multiple proteases. Our results suggest that the unusual diet of T. bisselliella larvae promotes their association with keratinolytic microorganisms and that the ability of larvae to feed on keratin can at least partially be attributed to bacteria that produce a cocktail of keratin-degrading enzymes.
What Does Ectoine Do to DNA? A Molecular-Scale Picture of Compatible Solute−Biopolymer Interactions
(2020)
Compatible solutes are accumulated in the cytoplasm of halophilic microorganisms. These molecules enable their survival in a high salinity environment. Ectoine is such a compatible solute. It is a zwitterionic molecule which strongly interacts with surrounding water molecules and changes the dynamics of the local hydration shell. Ectoine interacts with biomolecules such as lipids, proteins and DNA. The molecular interaction between ectoine and biomolecules in particular the interaction between ectoine and DNA is far from being understood.
In this paper we describe molecular aspects of the interaction between ectoine and double stranded DNA(dsDNA). Two 20 base pairs long dsDNA fragments were immobilized on a Gold surface via a thiol-tether. The interaction between the dsDNA monolayers with diluted and concentrated ectoine solutions was examined by means of X-ray photoelectron and polarization modulation infrared reflection absorption spectroscopies (PM IRRAS). Experimental results indicate that the ability of ectoine to bind water reduces the strength of hydrogen bonds formed to the ribose-phosphate backbone in the dsDNA. In diluted (0.1 M) ectoine solution, DNA interacts predominantly with water molecules. The sugar-phosphate backbone is involved in the formation of strong hydrogen bonds to water, which with elapsing time leads to a reorientation of the planes of nucleic acid bases. This reorientation destabilizes the hydrogen bonds strength between the bases and leads to a partial dehybridizaiton of the dsDNA. In concentrated ectoine solution (2.5 M), almost all water molecules interact with ectoine. Under this condition ectoine is able to interact directly with DNA. Density functional theory (DFT) calculations demonstrate that the direct interaction involves the nitrogen atoms in ectoine and phosphate groups in the DNA molecule. The results of the quantum chemical calculations Show that rearrangements in the ribose-phosphate backbone, caused by a direct interaction with ectoine, facilitates contacts between O atom in the phosphate group and H atoms in a nucleic acid base. In the PM IRRA spectra, an increase in the number of the IR absorption modes in the base pair frequency region proves that the hydrogen bonds between bases become weaker.
Thus, a sequence of reorientations caused by interaction with ectoine leads to a breakdown of hydrogen bonds between bases in the double helix.
This study investigated the adaptation of the state-of-the-art test procedure for the determination of emissions of volatile organic compounds (VOC) from materials into indoor air to test for the radon exhalation from stony construction products. A complete robustness validation including all relevant parameters showed that the procedure can be well applied by testing institutes already holding available the required VOC testing infrastructure that solely needs to be complemented by calibrated commercial radon measurement instrumentation. When measurements of the radon exhalation from construction materials become mandatory by law, test capacity can easily be applied. This work can serve as a recommendation for the European standardisation that still is on hold in this point.
Microspectroscopy reveals dust-derived apatite grains in acidic, highly-weathered Hawaiian soils
(2021)
Dust deposition is an important source of phosphorus (P) to many ecosystems. However, there is little evidence of dust-derived P-containing minerals in soils. Here we studied P forms along a well-described climatic Gradient on Hawaii, which is also a dust deposition gradient. Soil mineralogy and soil P forms from six sites along the climatic gradient were analyzed with bulk (X-ray diffraction and P K-edge X-ray absorption near edge structure) and microscale (X-ray fluorescence, P K-edge X-ray absorption near edge structure, and Raman) analysis methods. In the wettest soils, apatite grains ranging from 5 to 30 μm in size were co-located at the micro-scale with quartz, a known continental dust indicator suggesting recent atmospheric deposition. In addition to co-location with quartz, further evidence of dust-derived P included backward trajectory modeling indicating that dust particles could be brought to Hawaii from the major global dust-loading areas in central Asia and northern Africa. Although it is not certain whether the individual observed apatite grains were derived from long-distance transport of dust, or from local dust sources such as volcanic ash or windblown fertilizer, these observations offer direct evidence that P-containing minerals have reached surface layers of highly-weathered grassland soils through atmospheric deposition.
One of the typical wastes produced in blast-furnace (BF) ironmaking is BF sludge, which mostly consists of carbon and iron oxides, but also contains toxic trace metals such as Zn, Pb, Cd, As, and Hg that render the material hazardous. Due to the lack of an established recycling process, BF sludges are landfilled, which is ecologically questionable and costly. Here, we investigate selective removal of Zn, Pb, and Cd from BF sludge by chlorination–evaporation reactions using thermodynamic modelling and laboratory-scale experiments. Specifically, BF sludge was thermochemically treated at 650–1000 °C with a spent iron(II) chloride solution from steel pickling and the effects of process temperature and retention time on removal of Zn, Pb, and Cd were investigated. Zinc and Pb were quantitatively removed from BF sludge thermochemically treated at 900–1000 °C, whereas Fe and C as well as other major elements were mostly retained. The Zn, Pb, and Cd contents in the thermochemically treated BF sludge could be lowered from ∼56 g/kg, ∼4 g/kg, and ∼0.02 g/kg to ≤0.7 g/kg, ≤0.02 g/kg, and ≤0.008 g/kg, respectively, thus rendering the processed mineral residue a non-hazardous raw material that may be re-utilized in the blast furnace or on the sinter band.