Proof of the Riemann Hypothesis

The Riemann hypothesis, stating that the real part of all non-trivial zero points fo the zeta function must be $\frac{1}{2}$, is one of the most important unproven hypothesises in number theory. In this paper we will proof the Riemann hypothesis by using the integral representation $\zeta(s)=\frac{s}{s-1}-s\int_{1}^{\infty}\frac{x-\lfloor x\rfloor}{x^{s+1}}\,\text{d}x$ and solving the integral for the real part of the zeta function

Minor impacts of reduced pH on bacterial biofilms on settlement tiles along natural pH gradients at two CO2 seeps in Papua New Guinea

Hassenrück C, Tegetmeyer H, Ramette A, Fabricius KE. Minor impacts of reduced pH on bacterial biofilms on settlement tiles along natural pH gradients at two CO2 seeps in Papua New Guinea. ICES Journal of Marine Science. 2017;74(4):978-987.Bacterial biofilms provide cues for the settlement of marine invertebrates such as coral larvae, and are therefore important for the resilience and recovery of coral reefs. This study aimed to better understand how ocean acidification may affect the community composition and diversity of bacterial biofilms on surfaces under naturally reduced pH conditions. Settlement tiles were deployed at coral reefs in Papua New Guinea along pH gradients created by two CO2 seeps. Biofilms on upper and lower tiles surfaces were sampled 5 and 13 months after deployment. Automated Ribosomal Intergenic Spacer Analysis was used to characterize 240 separate bacterial communities, complemented by amplicon sequencing of the bacterial 16S rRNA gene of 16 samples. Bacterial biofilms consisted predominantly of Alpha-, Gamma-, and Delta-proteobacteria, as well as Cyanobacteria, Flavobacteriia, and Cytophagia, whereas taxa that induce settlement of invertebrate larvae only accounted for a small fraction of the community. Bacterial biofilm composition was heterogeneous, with on average only similar to 25% of operational taxonomic units shared between samples. Among the observed environmental parameters, pH was only weakly related to community composition (R-2 similar to 1%), and was unrelated to community richness and evenness. In contrast, biofilms strongly differed between upper and lower tile surfaces (contrasting in light exposure and grazing intensity). There also appeared to be a strong interaction between bacterial biofilm composition and the macroscopic components of the tile community. Our results suggest that on mature settlement surfaces in situ, pH does not have a strong impact on the composition of bacterial biofilms. Other abiotic and biotic factors such as light exposure and interactions with other organisms may be more important in shaping bacterial biofilms on mature surfaces than changes in seawater pH

Rapid succession of uncultured marine bacterial and archaeal populations in a denitrifying continuous culture.

Kraft B, Tegetmeyer H, Meier D, Geelhoed JS, Strous M. Rapid succession of uncultured marine bacterial and archaeal populations in a denitrifying continuous culture. Environmental Microbiology. 2014;16(10):3275-3286.Marine denitrification constitutes an important part of the global nitrogen cycle and the diversity, abundance and process rates of denitrifying microorganisms have been the focus of many studies. Still, there is little insight in the ecophysiology of marine denitrifying communities. In this study, a heterotrophic denitrifying community from sediments of a marine intertidal flat active in nitrogen cycling was selected in a chemostat and monitored over a period of 50 days. The chemostat enabled the maintenance of constant and well-defined experimental conditions over the time-course of the experiment. Analysis of the microbial community composition by automated ribosomal intergenic spacer analysis (ARISA), Illumina sequencing and catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH) revealed strong dynamics in community composition over time, while overall denitrification by the enrichment culture was stable. Members of the genera Arcobacter, Pseudomonas, Pseudovibrio, Rhodobacterales and of the phylum Bacteroidetes were identified as the dominant denitrifiers. Among the fermenting organisms co-enriched with the denitrifiers was a novel archaeon affiliated with the recently proposed DPANN-superphylum. The pan-genome of populations affiliated to Pseudovibrio encoded a NirK as well as a NirS nitrite reductase, indicating the rare co-occurrence of both evolutionary unrelated nitrite reductases within coexisting subpopulations

Overcoming Data Scarcity in the Quality Control of Safety-Critical Fibre-Reinforced Composites by means of Transfer and Curriculum Learning

Fibre-reinforced composites are one promising material class to provide a response to the increasing environmental awareness within society. Due to their excellent lightweight potential, fibre-reinforced composites are preferably employed in safety-critical applications, requiring extensive quality control (QC). However, commercially available QC systems are only able to measure fibre deviations, not directly detecting the error itself. In consequence, a worker is required to perform a manual inspection. Artificial intelligence and especially convolutional neural networks (CNN) offer the opportunity to directly detect and classify defects. However, to train the corresponding algorithms large amounts of data are required, which are often inaccessible in production. Artificial augmentation of the available data is a popular approach to tackle this problem, yet, resulting most of the time in undesired overfitting of the CNN. Therefore, in this contribution we examine the transfer of human learning behaviour elements to algorithms in form of transfer learning (TL) and curriculum learning (CL). The overall aim is to research, whether CL and TL are appropriate approaches to address data scarcity in e.g. production environments. Therefore, we perform our research on the error detection of three-dimensional shaped fibre-reinforced textiles

Selective Pressure of Temperature on Competition and Cross-Feeding within Denitrifying and Fermentative Microbial Communities

Hanke A, Berg J, Hargesheimer T, Tegetmeyer H, Sharp CE, Strous M. Selective Pressure of Temperature on Competition and Cross-Feeding within Denitrifying and Fermentative Microbial Communities. Front. Microbiol. 2016;6: 1461.In coastal marine sediments, denitrification and fermentation are important processes in the anaerobic decomposition of organic matter. Microbial communities performing these two processes were enriched from tidal marine sediments in replicated, long term chemostat incubations at 10 and 25°C. Whereas denitrification rates at 25°C were more or less stable over time, at 10°C denitrification activity was unstable and could only be sustained either by repeatedly increasing the amount of carbon substrates provided or by repeatedly decreasing the dilution rate. Metagenomic and transcriptomic sequencing was performed at different time points and provisional whole genome sequences (WGS) and gene activities of abundant populations were compared across incubations. These analyses suggested that a temperature of 10°C selected for populations related to Vibrionales/Photobacterium that contributed to both fermentation (via pyruvate/formate lyase) and nitrous oxide reduction. At 25°C, denitrifying populations affiliated with Rhodobacteraceae were more abundant. The latter performed complete denitrification, and may have used carbon substrates produced by fermentative populations (cross-feeding). Overall, our results suggest that a mixture of competition-for substrates between fermentative and denitrifying populations, and for electrons between both pathways active within a single population -, and cross feeding-between fermentative and denitrifying populations-controlled the overall rate of denitrification. Temperature was shown to have a strong selective effect, not only on the populations performing either process, but also on the nature of their ecological interactions. Future research will show whether these results can be extrapolated to the natural environment

Quantification of the effects of ocean acidification on sediment microbial communities in the environment: the importance of ecosystem approaches

To understand how ocean acidification (OA) influences sediment microbial communities, naturally CO2-rich sites are increasingly being used as OA analogues. However, the characterization of these naturally CO2-rich sites is often limited to OA-related variables, neglecting additional environmental variables that may confound OA effects. Here, we used an extensive array of sediment and bottom water parameters to evaluate pH effects on sediment microbial communities at hydrothermal CO2 seeps in Papua New Guinea. The geochemical composition of the sediment pore water showed variations in the hydrothermal signature at seep sites with comparable pH, allowing the identification of sites that may better represent future OA scenarios. At these sites, we detected a 60% shift in the microbial community composition compared with reference sites, mostly related to increases in Chloroflexi sequences. pH was among the factors significantly, yet not mainly, explaining changes in microbial community composition. pH variation may therefore often not be the primary cause of microbial changes when sampling is done along complex environmental gradients. Thus, we recommend an ecosystem approach when assessing OA effects on sediment microbial communities under natural conditions. This will enable a more reliable quantification of OA effects via a reduction of potential confounding effects

Anaerobic digestion of the microalga Spirulina at extreme alkaline conditions: biogas production, metagenome, and metatranscriptome

Nolla Ardevol V, Strous M, Tegetmeyer H. Anaerobic digestion of the microalga Spirulina at extreme alkaline conditions: biogas production, metagenome, and metatranscriptome. Frontiers in Microbiology. 2015;6: 597.A haloalkaline anaerobic microbial community obtained from soda lake sediments was used to inoculate anaerobic reactors for the production of methane rich biogas. The microalga Spirulina was successfully digested by the haloalkaline microbial consortium at alkaline conditions (pH 10, 2.0 M Na+). Continuous biogas production was observed and the obtained biogas was rich in methane, up to 96 %. Alkaline medium acted as a CO2 scrubber which resulted in low amounts of CO2 and no traces of H2S in the produced biogas. A hydraulic retention time of 15 days and 0.25 g Spirulina L-1 day-1 organic loading rate were identified as the optimal operational parameters. Metagenomics and metatranscriptomics analysis showed that the hydrolysis of the supplied substrate was mainly carried out by Bacteroidetes of the “ML635J-40 aquatic group” while the hydrogenotrophic pathway was the main producer of methane in a methanogenic community dominated by Methanocalculus

Metagenome from a Spirulina digesting biogas reactor: analysis via binning of contigs and classification of short reads

Nolla Ardevol V, Peces M, Strous M, Tegetmeyer H. Metagenome from a Spirulina digesting biogas reactor: analysis via binning of contigs and classification of short reads. BMC Microbiology. 2015;15(1): 277.Background Anaerobic digestion is a biological process in which a consortium of microorganisms transforms a complex substrate into methane and carbon dioxide. A good understanding of the interactions between the populations that form this consortium can contribute to a successful anaerobic digestion of the substrate. In this study we combine the analysis of the biogas production in a laboratory anaerobic digester fed with the microalgae Spirulina, a protein rich substrate, with the analysis of the metagenome of the consortium responsible for digestion, obtained by high-throughput DNA sequencing. The obtained metagenome was also compared with a metagenome from a full scale biogas plant fed with cellulose rich material. Results The optimal organic loading rate for the anaerobic digestion of Spirulina was determined to be 4.0 g Spirulina L−1 day−1 with a specific biogas production of 350 mL biogas g Spirulina −1 with a methane content of 68 %. Firmicutes dominated the microbial consortium at 38 % abundance followed by Bacteroidetes, Chloroflexi and Thermotogae. Euryarchaeota represented 3.5 % of the total abundance. The most abundant organism (14.9 %) was related to Tissierella, a bacterium known to use proteinaceous substrates for growth. Methanomicrobiales and Methanosarcinales dominated the archaeal community. Compared to the full scale cellulose-fed digesters, Pfam domains related to protein degradation were more frequently detected and Pfam domains related to cellulose degradation were less frequent in our sample. Conclusions The results presented in this study suggest that Spirulina is a suitable substrate for the production of biogas. The proteinaceous substrate appeared to have a selective impact on the bacterial community that performed anaerobic digestion. A direct influence of the substrate on the selection of specific methanogenic populations was not observed

Horizontal acquisition of a patchwork Calvin cycle by symbiotic and free-living Campylobacterota (formerly Epsilonproteobacteria).

Assie A, Leisch N, Meier DV, et al. Horizontal acquisition of a patchwork Calvin cycle by symbiotic and free-living Campylobacterota (formerly Epsilonproteobacteria). The ISME journal. 2019;14(1):104-122.Most autotrophs use the Calvin-Benson-Bassham (CBB) cycle for carbon fixation. In contrast, all currently described autotrophs from the Campylobacterota (previously Epsilonproteobacteria) use the reductive tricarboxylic acid cycle (rTCA) instead. We discovered campylobacterotal epibionts ("Candidatus Thiobarba") of deep-sea mussels that have acquired a complete CBB cycle and may have lost most key genes of the rTCA cycle. Intriguingly, the phylogenies of campylobacterotal CBB cyclegenes suggest they were acquired in multiple transfers from Gammaproteobacteria closely related to sulfur-oxidizing endosymbionts associated with the mussels, as well as from Betaproteobacteria. We hypothesize that "Ca. Thiobarba" switched from the rTCA cycle to a fully functional CBB cycle during its evolution, by acquiring genes from multiple sources, including co-occurring symbionts. We also found key CBB cycle genes in free-living Campylobacterota, suggesting that the CBB cycle may be more widespread in this phylum than previously known. Metatranscriptomics and metaproteomics confirmed high expression of CBB cycle genes in mussel-associated "Ca. Thiobarba". Direct stable isotope fingerprinting showed that "Ca. Thiobarba" has typical CBB signatures, suggesting that it uses this cycle for carbon fixation. Our discovery calls into question current assumptions about the distribution of carbon fixation pathways in microbial lineages, and the interpretation of stable isotope measurements in the environment