2023-09-18, Ye, Huimin, Borusak, Sabrina, Eberl, Claudia, Krasenbrink, Julia, Weiss, Anna S., Chen, Song-Can, Hanson, Buck T., Hausmann, Bela, Herbold, Craig W., Schleheck, David

Taurine-respiring gut bacteria produce H 2 S with ambivalent impact on host health. We report the isolation and ecophysiological characterization of a taurine-respiring mouse gut bacterium. Taurinivorans muris strain LT0009 represents a new widespread species that differs from the human gut sulfidogen Bilophila wadsworthia in its sulfur metabolism pathways and host distribution. T. muris specializes in taurine respiration in vivo, seemingly unaffected by mouse diet and genotype, but is dependent on other bacteria for release of taurine from bile acids. Colonization of T. muris in gnotobiotic mice increased deconjugation of taurine-conjugated bile acids and transcriptional activity of a sulfur metabolism gene-encoding prophage in other commensals, and slightly decreased the abundance of Salmonella enterica , which showed reduced expression of galactonate catabolism genes. Re-analysis of metagenome data from a previous study further suggested that T. muris can contribute to protection against pathogens by the commensal mouse gut microbiota. Together, we show the realized physiological niche of a key murine gut sulfidogen and its interactions with selected gut microbiota members.

2018-07-18, Kunkel, Marius, Schildknecht, Stefan, Boldt, Klaus, Zeyffert, Lukas, Schleheck, David, Leist, Marcel, Polarz, Sebastian

The importation of construction principles or even constituents from biology into materials science is a prevailing concept. Vice versa, the cellular level modification of living systems with nonnatural components is much more difficult to achieve. It has been done for analytical purposes, for example, imaging, to learn something about intracellular processes. Cases describing the improvement of a biological function by the integration of a nonnatural (nano)constituent are extremely rare. Because biological membranes contain some kind of a surfactant, for example, phospholipids, our idea is to modify cells with a newly synthesized surfactant. However, this surfactant is intended to possess an additional functionality, which is the reduction of oxidative stress. We report the synthesis of a surfactant with Janus-type head group architecture, a fullerene C60 modified by five alkyl chains on one side and an average of 20 oxygen species on the other hemisphere. It is demonstrated that the amphiphilic properties of the fullerenol surfactant are similar to that of lipids. Not only quenching of reactive oxygen species (superoxide, hydroxyl radicals, peroxynitrite, and hydrogen peroxide) was successful, but also the fullerenol surfactant exceeds benchmark antioxidant agents such as quercetin. The surfactant was then brought into contact with different cell types, and the viability even of delicate cells such as human liver cells (HepG2) and human dopaminergic neurons (LUHMES) has proven to be extraordinarily high. We could show further that the cells take up the fullerenol surfactant, and as a consequence, they are protected much better against oxidative stress.

2014, Gehring, Julia, Schleheck, David, Luka, Martin, Polarz, Sebastian

Combining high internal surface area with tailor-made surface properties is pivotal for granting advanced functional properties in many areas like heterogeneous catalysis, electrode materials, membranes, or also biomimetics. In this respect, organic-inorganic hybrid nanostructures and in particular mesoporous organosilica materials are ideal systems. Here, the preparation of mesoporous solids via a new sol–gel building block comprising sulfonic acid (R-SO3H) is described. The degree of organic modification is not only maximal (100%), it is also proven that the novel material exhibits superacid properties. Furthermore, an aerosol assisted method is applied for generating this material in the form of mesoporous, spherical nanoparticles with substantial colloidal stability. Highly acidic, high surface area materials, like prepared here, are promising candidates for numerous future applications like in heterogeneous catalysis or for proton conducting membranes. However, first experiments addressing the antibacterial effect of the sulfonic-acid, mesoporous organosilica materials are shown. It is demonstrated that the superacid character is required for exhibiting sufficient antifouling activity.

2012-11, Mayer, Jutta, Denger, Karin, Hollemeyer, Klaus, Schleheck, David, Cook, Alasdair M.

Cupriavidus necator H16 grew exponentially with (R)-cysteate, a structural analogue of aspartate, as sole source of nitrogen in succinate-salts medium. Utilization of cysteate was quantitative and concomitant with growth and with the excretion of the deaminated product (R)-sulfolactate, which was identified thoroughly. The deaminative pathway started with transport of (R)-cysteate into the cell, which we attributed to an aspartate transporter. Transamination to sulfopyruvate involved an aspartate/(R)-cysteate:2-oxoglutarate aminotransferase (Aoa/Coa) and regeneration of the amino group acceptor by NADP⁺-coupled glutamate dehydrogenase. Reduction of sulfopyruvate to (R)-sulfolactate was catalyzed by a (S)-malate/(R)-sulfolactate dehydrogenase (Mdh/Sdh). Excretion of the sulfolactate could be attributed to the sulfite/organosulfonate exporter TauE, which was co-encoded and co-expressed, with sulfoacetaldehyde acetyltransferase (Xsc), though Xsc was irrelevant to the current pathway. The metabolic enzymes could be assayed biochemically. Aoa/Coa and Mdh/Sdh were highly enriched by protein separation, partly characterized, and the relevant locus-tags identified by peptide-mass fingerprinting. Finally, RT-PCR was used to confirm the transcription of all appropriate genes. We thus demonstrated that Cupriavidus necator H16 uses a patchwork pathway by recruitment of 'housekeeping' genes and sulfoacetaldehyde-degradative genes to scavenge for (R)-cysteate-nitrogen.

2023-08, Mao, Zhuqing, Müller, Nicolai, Borusak, Sabrina, Schleheck, David, Schink, Bernhard

Phosphite is a stable phosphorus compound that, together with phosphate, made up a substantial part of the total phosphorus content of the prebiotic Earth's crust. Oxidation of phosphite to phosphate releases electrons at an unusually low redox potential (−690 mV at pH 7.0). Numerous aerobic and anaerobic bacteria use phosphite as a phosphorus source and oxidise it to phosphate for synthesis of nucleotides and other phosphorus-containing cell constituents. Only two pure cultures of strictly anaerobic bacteria have been isolated so far that use phosphite as an electron donor in their energy metabolism, the Gram-positive Phosphitispora fastidiosa and the Gram-negative Desulfotignum phosphitoxidans. The key enzyme of this metabolism is an NAD+-dependent phosphite dehydrogenase enzyme that phosphorylates AMP to ADP. These phosphorylating phosphite dehydrogenases were found to be related to nucleoside diphosphate sugar epimerases. The produced NADH is channelled into autotrophic CO2 fixation via the Wood-Ljungdahl (CO-DH) pathway, thus allowing for nearly complete assimilation of the substrate electrons into bacterial biomass. This extremely efficient type of electron flow connects energy and carbon metabolism directly through NADH and might have been important in the early evolution of life when phosphite was easily available on Earth.

2016, Gehring, Julia, Trepka, Bastian, Klinkenberg, Nele, Bronner, Hannah, Schleheck, David, Polarz, Sebastian

Colonization of surfaces by microorganisms is an urging problem. In combination with the increasing antibiotic resistance of pathogenic bacteria, severe infections are reported more frequently in medical settings. Therefore, there is a large demand to explore innovative surface coatings that provide intrinsic and highly effective antibacterial activity. Materials containing silver nanoparticles have been developed in the past for this purpose, but this solution has come into criticism due to various disadvantages like notable toxicity against higher organisms, the high price, and low abundance of silver. Here, we introduce a new, sunlight-mediated organosilica nanoparticle (NP) system based on silver-free antibacterial activity. The simultaneous release of nitric oxide (NO) in combination with singlet oxygen and superoxide radicals (O₂^•-) as reactive oxygen species (ROS) leads to the emergence of highly reactive peroxynitrite molecules with significantly enhanced biocidal activity. This special cooperative effect can only be realized, if the ROS-producing moieties and the functional entities releasing NO are spatially separated from each other. In one type of particle, Rose Bengal as an efficient singlet oxygen (¹O₂) producer was covalently bound to SH functionalities applying thiol-ene click chemistry. "Charging" the second type of particles with NO was realized by quantitatively transferring the thiol groups into S-nitrosothiol functionalities. We probed the oxidation power of ROS-NP alone and in combination with NO-NP using sunlight as a trigger. The high antibacterial efficiency of dual-action nanoparticles was demonstrated using disinfection assays with the pathogenic bacterium Pseudomonas aeruginosa.

2013-06, Felux, Ann-Katrin, Denger, Karin, Weiss, Michael, Cook, Alasdair M., Schleheck, David

Hypotaurine (HT, 2-aminoethane-sulfinate) is known to be utilized by bacteria as a sole source of carbon, nitrogen and energy for growth, as is taurine (2-aminoethane-sulfonate), however, the corresponding HT-degradation pathway remained undefined. Genome-sequenced Paracoccus denitrificans PD1222 utilized HT (and taurine) quantitatively for heterotrophic growth and released the HT-sulfur as sulfite (and sulfate), and HT-nitrogen as ammonium. Enzyme assays with cell-free extracts suggested that a HT-inducible HT:pyruvate aminotransferase (Hpa) catalyzes the deamination of HT in an initial reaction step. Partial purification of the Hpa activity and peptide fingerprinting-mass spectrometry (PF-MS) identified the Hpa-candidate gene; it encoded an archetypal taurine:pyruvate aminotransferase (Tpa). The same gene-product was identified via differential PAGE and PF-MS, as well as the gene of a strongly HT-inducible aldehyde dehydrogenase (Adh). Both genes were overexpressed in E. coli. The overexpressed, purified Hpa/Tpa showed HT:pyruvate-aminotransferase activity. Alanine, acetaldehyde, and sulfite, were identified as the reaction products, but not sulfinoacetaldehyde; the reaction of Hpa/Tpa with taurine yielded sulfoacetaldehyde, which is stable. The overexpressed, purified Adh oxidized the acetaldehyde generated during the Hpa reaction to acetate in an NAD+-dependent reaction. Based on these results, the following degradation pathway for HT in strain PD1222 can be depicted. The identified aminotransferase converts HT to sulfinoacetaldehyde, which desulfinates spontaneously to acetaldehyde and sulfite; the inducible aldehyde dehydrogenase oxidizes acetaldehyde to yield acetate, which is metabolized, and sulfite, that is excreted.

2023-07-19, Avasthi, Ilesha, Lerner, Harry, Grings, Jonas, Gräber, Carla, Schleheck, David, Cölfen, Helmut

Mineral plastics are a promising class of bio-inspired materials that offer exceptional properties, like self-heal ability, stretchability in the hydrogel state, and high hardness, toughness, transparency, and non-flammability in the dry state along with reversible transformation into the hydrogel by addition of water. This enables easy reshape-ability and recycling like the solubility in mild acids to subsequently form mineral plastics again by base addition. However, current mineral plastics rely on petrochemistry, are hardly biodegradable, and thus persistent in nature. This work presents the next generation of mineral plastics, which are bio-based and biodegradable, making them a promising, new class of polymers for the development of environmentally friendly materials. Physically cross-linked (poly)glutamic-acid (PGlu)-based mineral plastics are synthesized using various alcohol-water mixtures, metal ion ratios and molecular weights. The rheological properties are easily adjusted using these parameters. The general procedure involves addition of equimolar solution of CaCl₂ to PGlu in equal volumes followed by addition of iPrOH (iPrOH:H₂O = 1:1) under vigorous stirring conditions. The ready biodegradability of PGlu/CaFe mineral plastic is confirmed in this study where the elements N, Ca, and Fe present in it tend to act as additional nutrients, supporting the growth of microorganisms and consequently, promoting the biodegradation process.

2015, Gehring, Julia, Schleheck, David, Trepka, Bastian, Polarz, Sebastian

A superior degree of functionality in materials can be expected, if two or more operational entities are related in a cooperative form. It is obvious that, for this purpose, one is seeking materials with complex design comprising bi- or multiple functional groups complementing each other. In the current paper, it is demonstrated that periodically ordered mesoporous organosilicas (PMOs) based on co-condensation of sol–gel precursors with bridging phenyl derivatives R_F1,2C₆H₃[Si(Oi^soPr)₃]₂ allow for rich opportunities in providing high-surface area materials with such a special chemical architecture. PMOs containing high density of thiol (≅ R_F1) and sulfonic acid units (≅ R_F2) were prepared as mesoporous nanoparticles via an aerosol-assisted gas-phase method and were tested for biocidal applications. Each of the mentioned organic groups fulfills several tasks at once. The selective functionalization of thiols located at the surface of the particles using click chemistry leads to durable grafting on different substrates like glass or stainless steel, and the intraparticle −SH groups are important regarding the uptake of metal ions like Ag⁺ and for immobilization of Ag⁰ nanoparticles inside the pores as an enduring reservoir for antibacterial force. The superacidic sulfonic acid groups exhibit a strong and instantaneous biocidal acitivity, and they are important for adjusting the Ag⁺ release rate. Biological studies involving inhibitory investigation tests (MIC), fluorescence microscopy (life/dead staining), and bacterial adhesion tests with Pseudomonas aeruginosa show that the organobifunctional materials present much better performance against biofilm formation compared to materials containing only one of the above-mentioned groups.

2013-04, Kesberg, Anna Isabella, Schleheck, David

Extraction of bacterial DNA from water filters is frequently used in aquatic microbial ecology, e.g., for sequencing-based diversity studies. Here, we describe an improved size-class filtration and bacterial DNA extraction protocol using commercial "syringe filters", involving sonication- and backflushing-steps and DNA-binding magnetic beads. Importantly, the sonication-step improved DNA recovery up to 10-fold. The DNA extraction-turnaround time is 4h, with a hands-on time of about 2h.