4 Material und Umwelt
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Insecta is one of the most diverse phyla in the animal kingdom, with species living in all types of habitats encountering an even greater diversity of pathogens and parasites. Defence strategies against such harmful threats led to a variety of molecular mechanisms, ecological shifts, and genetic innovations. Gene families underlying the molecular basis of the immune responses have evolved within the boundaries given by the species ecology. Here, we explore the evolution of some emblematic immune gene families throughout the Insecta phylum shedding light on remarkable genetic events such as gene duplication or gene loss. We followed a workflow based on the Hidden Markov model to search for immune genes in 55 high-quality genomes of insects. We highlight the emergence of group defence in social species as an ecological shift that released selection pressure on immune gene families notably in Blattodea. Further, we draw attention to certain gene families and the link between their diversity and the specificities of the species’ microbiota. Overall, we report data on immune gene diversity in insects.
Adipokinetic hormone (AKH) is a neuropeptide produced in the insect corpora cardiaca that plays an essential role in mobilizing carbohydrates and lipids from the fat body to the hemolymph. AKH acts by binding to a rhodopsin-like G protein-coupled receptor (GPCR), the adipokinetic hormone receptor (AKHR). In this study, we tackle AKH ligand and receptor gene evolution as well as the evolutionary origins of AKH gene paralogues from the order Blattodea (termites and cockroaches). Phylogenetic analyses of AKH precursor sequences point to an ancient AKH gene duplication event in the common ancestor of Blaberoidea, yielding a new group of putative decapeptides. In total, 16 different AKH peptides from 90 species were obtained. Two octapeptides and seven putatively novel decapeptides are predicted for the first time. AKH receptor (AKHRs) sequences from 18 species, spanning solitary cockroaches and subsocial woodroaches as well as lower and higher termites, were subsequently acquired using classical molecular methods and in silico approaches employing transcriptomic data. Aligned AKHR open reading frames revealed 7 highly conserved transmembrane regions, a typical arrangement for GPCRs. Phylogenetic analyses based on AKHR sequences support accepted relationships among termite and cockroach lineages to a large extent, while putative post-translational modification sites do not greatly differ between solitary and subsocial roaches and social termites. This study provides important information not only for AKH and AKHR functional research but also for further analyses interested in their development as potential candidates for biorational pest control agents against invasive termites and cockroaches.
Regional standardisation activities and how VAMAS can help in any way to promote activities are reported.
Activities related to organisational updates, government initiatives/priorities (especially related to Materials), details of any strategy documents publicly available, networks within Germany and how we engage are presented.
The amount of plant-available phosphorus (P) in soil strongly influences the yield of plants in agriculture. Therefore, various simple chemical extraction methods have been developed to estimate the plant-available P pools in soil. More recently, several experiments with the DGT technique have shown that it has a much better correlation to plant-available P in soils than standard chemical extraction methods (e.g. calcium-acetate-lactate (CAL), Colwell, Olsen, water) when soils with different characteristics are considered. However, the DGT technique cannot give information on the plant-available P species in the soil. Therefore, we combined DGT with solution 31P nuclear magnetic resonance (NMR) spectroscopy. This was achieved by using a modified DGT device in which the diffusive layer had a larger pore size, the binding layer incorporated an adsorption material with a higher capacity, and the device had a larger exposure area. The spectroscopic investigation was undertaken after elution of the deployed DGT binding layer in a NaOH solution. Adsorption tests using solutions of known organic P compounds showed that a sufficient amount of these compounds could be adsorbed on the binding layer in order for them to be analyzed by solution 31P NMR spectroscopy. Furthermore, various intermediates of the hydrolysis of trimetaphosphate in soil could be also analyzed over time.
Surfaces of metallic copper and copper alloys effectively inactivate microorganisms and viruses. However, the exact inactivation mode is still under debate. Main factors are assumed to include direct contact with the metallic surface, influx of Cu(I)/Cu(II) ions and the generation of reactive oxygen species (ROS). Laser-induced periodic surface structures (LIPSS) are frequently reported to act antibacterial, mainly by prevention of bacterial adhesion due to a limited number of possible adhesion points or by increasing the overall surface of intrinsically antibacterial materials. In time-kill experiments with E. coli and S. aureus we analyzed the impact of LIPSS on the toxicity of metallic copper and brass. We also conducted ROS accumulation assays and conclude that the application of LIPSS is not generally straight forward to obtain or improve antibacterial surfaces. Thus, the antibacterial effects of LIPPS.
Background. Disinfection is an important mitigation strategy to control and prevent the spread of infections. Incomplete or incorrect usage of disinfection may promote evolution of resistance against disinfectants and antibiotics. Ideally, disinfection reduces the number of surviving bacteria and the chance for resistance evolution. Resistance describes the ability to grow in previously inhibitory concentrations of an antimicrobial, whereas tolerance is associated with enhanced survival of lethal doses. Individual bacteria from the same population can display considerable heterogeneity in their ability to survive treatment (i.e. tolerance) with antimicrobials, which can result in unexpected treatment failure.
Objective. In this study, we investigated six active substances of disinfectants, preservatives, and antiseptics against a population of E. coli to identify the presence of a tolerant subpopulation.
Methods. We performed time-kill experiments and analyzed the data with a mathematical model to statistically infer whether the data is best explained by the presence of a tolerant subpopulation.
Results. The analysis identified bimodal kill kinetics for benzalkonium chloride, didecyldimethylammonium chloride, and isopropanol. In contrast, kill kinetics by chlorhexidine, glutaraldehyde, and hydrogen peroxide were best explained by unimodal kill kinetics. These findings have implications for the risk of disinfection failure. In addition, we are currently performing adaptive laboratory evolution (ALE) experiments with the different disinfectants to investigate the potential consequences of tolerant sub-populations for the evolution of antimicrobial resistance and tolerance.
Background. Disinfection is an important mitigation strategy to control and prevent the spread of infections. Incomplete or incorrect usage of disinfection may promote evolution of resistance against disinfectants and antibiotics. Ideally, disinfection reduces the number of surviving bacteria and the chance for resistance evolution. Resistance describes the ability to grow in previously inhibitory concentrations of an antimicrobial, whereas tolerance is associated with enhanced survival of lethal doses. Individual bacteria from the same population can display considerable heterogeneity in their ability to survive treatment (i.e. tolerance) with antimicrobials, which can result in unexpected treatment failure.
Objective. In this study, we investigated six active substances of disinfectants, preservatives, and antiseptics against a population of E. coli to identify the presence of a tolerant subpopulation.
Methods. We performed time-kill experiments and analyzed the data with a mathematical model to statistically infer whether the data is best explained by the presence of a tolerant subpopulation.
Results. The analysis identified bimodal kill kinetics for benzalkonium chloride, didecyldimethylammonium chloride, and isopropanol. In contrast, kill kinetics by chlorhexidine, glutaraldehyde, and hydrogen peroxide were best explained by unimodal kill kinetics. These findings have implications for the risk of disinfection failure. In addition, we are currently performing adaptive laboratory evolution (ALE) experiments with the different disinfectants to investigate the potential consequences of tolerant sub-populations for the evolution of antimicrobial resistance and tolerance.
Biocides are used for a wide range of purposes, including disinfectants or preservatives. They play a major role in the prevention of microbial infections in healthcare and animal husbandry. The use of biocides often leads to the discharge of active biocidal substances into wastewater streams, causing the exposure of wastewater microbial communities to subinhibitory concentrations. In turn, it is known that wastewater treatment plants (WWTP) are hotspots for antibiotic resistant bacteria. Since similar mechanisms confer resistance to biocides and antibiotics, exposure to biocides can result in co-selection of antibiotic resistant bacteria in WWTP Here, we want to investigate co-selection processes of antibiotic resistance in natural WWTP microbial communities upon biocide exposure. Microbial communities were sampled at the WWTP Ruhleben in Berlin and characterized regarding their susceptibility against different clinically relevant antibiotics. To investigate the link between biocide exposure and antibiotic resistance, changes in the susceptibility level after exposure to environmentally relevant concentrations of the commonly used biocide didecyldimethylammonium chloride (DDAC) will be determined by enumerating resistant and non-resistant E. coli on selective plates with and without antibiotics and DDAC. In case of antibiotics, clinical breakpoint concentrations according to EUCAST will be used to discriminate between susceptible and resistant strains. In case of DDAC (and biocides in general), clinical breakpoints do not exist. Therefore, we determined a cut-off concentration at which the majority of naturally-occurring E. coli strains cannot grow anymore based on (I) the MIC (minimal inhibitory concentration) distribution, and (II) by plating wastewater communities onto selective indicator agar plates loaded with increasing DDAC concentration. Additionally, antibiotic cross-resistance will be determined by spotting single colonies, isolated from DDAC-selective plates onto antibiotic plates. The results of our experiments will help to determine selective concentrations and to estimate the risk of antibiotic co-selection and cross-resistance in microbial WWTP communities upon biocide exposure.
Steelmaking slag is a by-product of steel production of which 4.5 Mt were produced in 2020 in Germany alone. It is mainly used in road construction, earthwork and hydraulic engineering. A smaller part is returned to the metallurgical circle, used as fertilizer or landfilled.
With this use, iron oxides still contained in steelmaking slag are lost. In addition, the possibility of producing higher-grade products from steelmaking slag is foregone. In recent decades, many researchers have investigated the production of Portland cement clinker and crude iron from basic oxygen furnace slags (BOFS) via a reductive treatment. Carbothermal treatment of liquid BOFS causes a reduction of iron oxides to metallic iron, which separates from the mineral phase due to its higher density. Simultaneously, the chemical composition of the reduced slag is adapted to that of the Portland cement clinker.
In this study, German BOFS was reduced in a small-scale electric arc furnace using petrol coke as a reducing agent. The resulting low-iron mineral product had a similar chemical composition to Portland cement clinker and was rich in the tricalcium silicate solid solution alite (Ca3SiO5). Based on its chemical and mineralogical composition, similar to that of Portland cement clinker, the reduced BOFS has the potential to react comparably. In our study, the reduced BOFS produced less heat of hydration compared to OPC and its hydraulic reaction was delayed. However, adding gypsum has been shown to accelerate the hydration rate of the reduced BOFS compared to that known from the calcium silicates of Portland cement clinker.
Further research to improve the hydraulic properties of the reduced slag is essential. If successful, producing a hydraulic binder and crude iron from BOFS could have economic and ecological benefits for both the cement and steel industry.
Melanins are organic pigments produced by most fungi. These organisms either fix these pigments in their cell wall or secrete them into their extracellular environment to protect themselves against an array of physicochemical stresses (e.g., UV irradiation, desiccation, ...). Melanin can adsorb metals like Fe. How this affects fungal uptake of Fe and deterioration of Fe-containing minerals and metals is however less known. To study this, we use the model fungi Knufia petricola A95, a rock-inhabiting fungus known to deteriorate minerals and have melanised cell walls, and Amorphotheca resinae, able to contaminate fuel tanks, secrete melanin and corrode metals. In K. petricola, we have deleted genes involved in melanin production and Fe uptake using CRISPR/Cas. Through comparison of the geochemical signatures of these gene deletion mutants with those of the wild type (WT), we explore the specific mineral/metal deterioration mechanisms of melanised fungi.
Fe isotope signatures of the biomass of melanin- and Fe uptake-deficient mutants of K. petricola revealed that Fe adsorbed either directly onto melanin or after being reduced by Fe reductases. Importantly, once adsorbed to melanin, Fe could not be mobilised and taken up into the cell: both the WT and its melanin-deficient mutant, previously grown at Fe replete conditions, showed similar growth at Fe deficient conditions.
Olivine dissolution experiments revealed that Fe oxidation inhibits dissolution. K. petricola was able to enhance dissolution when this inhibition is strongest (at pH 6) and prevented dissolution when this inhibition is weakest (at pH 4). The fungus therefore dissolves olivine by interacting with the oxidised Fe at the olivine surface. However, Fe uptake did not seem to be involved: mutants deficient in various Fe uptake mechanism dissolved olivine at the same rate as the WT. This indicates that Fe adsorption onto melanin might play a key role. This is also shown by K. petricola’s ability to enhance olivine dissolution even further if secreting a melanin precursor and A. resinae’s corrosion of carbon steel whilst secreting melanin. Combined, our results imply that the Fe adsorbed to melanin cannot be taken up but enables fungi to deteriorate Fe-containing substrates at a higher rate.