Analytical Fresnel laws for curved dielectric interfaces

Fresnel laws and the corresponding Fresnel reflection and transmission coefficients provide the quantitative information of the amount of reflected and transmitted (refracted) light in dependence on its angle of incidence. They are at the core of ray optics at planar interfaces. However, the wellknown Fresnel formulae do not hold at curved interfaces and deviations are appreciable when the radius of curvature becomes of the order of several wavelengths of the incident light. This is of particular importance for optical microcavities that play a significant role in many modern research fields. Their convexly curved interfaces modify Fresnel’s law in a characteristic manner. Most notably, the onset of total internal reflection is shifted to angles larger than critical incidence (Martina and Henning 2002 Phys. Rev. E 65 045603). Here, we derive analytical Fresnel formulae for the opposite type of interface curvature, namely concavely curved refractive index boundaries, that have not been available so far. The accessibility of curvature-dependent Fresnel coefficients facilitates the analytical, ray-optics based description of light in complex mesoscopic optical structures that will be important in future nano- and microphotonic applications

Bewegungs- und Verschleißverhalten von Hartmetalllamellen bei der Betonbearbeitung

Die vorliegende Forschungsarbeit beinhaltet eine Analyse zum Bewegungs- und Verschleißverhalten von Hartmetalllamellen bei der Betonbearbeitung. Experimentelle und numerische Untersuchungen dienen in dieser Arbeit zur Modell-Verifizierung sowie zur Definition der Verschleißcharakteristika

Emerging Sponge Models of Animal-Microbe Symbioses

Sponges have a significant impact on marine benthic communities, they are of biotechnological interest owing to their production of bioactive natural compounds, and they promise to provide insights into conserved mechanisms of host–microbe interactions in basal metazoans. The natural variability of sponge-microbe associations across species and environments provides a meaningful ecological and evolutionary framework to investigate animal-microbial symbiosis through experimentation in the field and also in aquaria. In addition, next-generation sequencing technologies have shed light on the genomic repertoire of the sponge host and revealed metabolic capacities and symbiotic lifestyle features of their microbiota. However, our understanding of symbiotic mechanisms is still in its infancy. Here, we discuss the potential and limitations of the sponge-microbe symbiosis as emerging models for animal-associated microbiota

Bdellovibrio and Like Organisms Are Predictors of Microbiome Diversity in Distinct Host Groups

Biodiversity is generally believed to be a main determinant of ecosystem functioning. This principle also applies to the microbiome and could consequently contribute to host health. According to ecological theory, communities are shaped by top predators whose direct and indirect interactions with community members cause stability and diversity. Bdellovibrio and like organisms (BALOs) are a neglected group of predatory bacteria that feed on Gram-negative bacteria and can thereby influence microbiome composition. We asked whether BALOs can predict biodiversity levels in microbiomes from distinct host groups and environments. We demonstrate that genetic signatures of BALOs are commonly found within the 16S rRNA reads from diverse host taxa. In many cases, their presence, abundance, and especially richness are positively correlated with overall microbiome diversity. Our findings suggest that BALOs can act as drivers of microbial alpha-diversity and should therefore be considered candidates for the restoration of microbiomes and the prevention of dysbiosis

Endophytes Are Hidden Producers of Maytansine in Putterlickia Roots

Several recent studies have lent evidence to the fact that certain so-called plant metabolites are actually biosynthesized by associated microorganisms. In this work, we show that the original source organism(s) responsible for the biosynthesis of the important anticancer and cytotoxic compound maytansine is the endophytic bacterial community harbored specifically within the roots of Putterlickia verrucosa and P. retrospinosa plants. Evaluation of the root endophytic community by chemical characterization of their fermentation products using HPLC-HRMSn, along with a selective microbiological assay using the maytansine-sensitive type strain Hamigera avellanea revealed the endophytic production of maytansine. This was further confirmed by the presence of AHBA synthase genes in the root endophytic communities. Finally, MALDI-imaging-HRMS was used to demonstrate that maytansine produced by the endophytes is typically accumulated mainly in the root cortex of both plants. Our study, thus, reveals that maytansine is actually a biosynthetic product of root-associated endophytic microorganisms. The knowledge gained from this study provides fundamental insights on the biosynthesis of so-called plant metabolites by endophytes residing in distinct ecological niches

Predicted bacterial interactions affect in vivo microbial colonization dynamics in Nematostella

The maintenance and resilience of host-associated microbiota during development is a fundamental process influencing the fitness of many organisms. Several host properties were identified as influencing factors on bacterial colonization, including the innate immune system, mucus composition and diet. In contrast, the importance of bacteria-bacteria interactions on host colonization is less understood. Here, we use bacterial abundance data of the marine model organism Nematostella vectensis to reconstruct potential bacteria-bacteria interactions through co-occurrence networks. The analysis indicates that bacteria-bacteria interactions are dynamic during host colonization and change according to the host’s developmental stage. To assess the predictive power of inferred interactions, we tested bacterial isolates with predicted cooperative or competitive behavior for their ability to influence bacterial recolonization dynamics. Within three days of recolonization all tested bacterial isolates affected bacterial community structure, while only competitive bacteria increased bacterial diversity. Already one week after recolonization almost no differences in bacterial community structure could be observed between control and treatments. These results show that predicted competitive bacteria can influence community structure for a short period of time, verifying the in silico predictions. However, within one week, the effects of the bacterial isolates are neutralized, indicating a high degree of resilience of the bacterial community. Hanna Domin1, Yazmín H. Zurita-Gutiérrez2, Marco Scotti3, Jann Buttlar1, Ute Hentschel Humeida2 and Sebastian Fraune1

Shedding light on cell compartmentation in the candidate phylum Poribacteria by high resolution visualisation and transcriptional profiling

Assigning functions to uncultivated environmental microorganisms continues to be a challenging endeavour. Here, we present a new microscopy protocol for fluorescence in situ hybridisation-correlative light and electron microscopy (FISH-CLEM) that enabled, to our knowledge for the first time, the identification of single cells within their complex microenvironment at electron microscopy resolution. Members of the candidate phylum Poribacteria, common and uncultivated symbionts of marine sponges, were used towards this goal. Cellular 3D reconstructions revealed bipolar, spherical granules of low electron density, which likely represent carbon reserves. Poribacterial activity profiles were retrieved from prokaryotic enriched sponge metatranscriptomes using simulation-based optimised mapping. We observed high transcriptional activity for proteins related to bacterial microcompartments (BMC) and we resolved their subcellular localisation by combining FISH-CLEM with immunohistochemistry (IHC) on ultra-thin sponge tissue sections. In terms of functional relevance, we propose that the BMC-A region may be involved in 1,2-propanediol degradation. The FISH-IHC-CLEM approach was proven an effective toolkit to combine -omics approaches with functional studies and it should be widely applicable in environmental microbiology

A Phage Protein Aids Bacterial Symbionts in Eukaryote Immune Evasion

Highlights: • Sponges, evolutionary basal animals, represent a reservoir of novel viral diversity • Viromes of neighboring sponges are individually unique and species specific • Phages encode ankyrins to aid bacteria in evading the eukaryotic immune system • Such “Ankyphages” are widespread in host-associated environments, including humans Summary: Phages are increasingly recognized as important members of host-associated microbiomes, with a vast genomic diversity. The new frontier is to understand how phages may affect higher order processes, such as in the context of host-microbe interactions. Here, we use marine sponges as a model to investigate the interplay between phages, bacterial symbionts, and eukaryotic hosts. Using viral metagenomics, we find that sponges, although massively filtering seawater, harbor species-specific and even individually unique viral signatures that are taxonomically distinct from other environments. We further discover a symbiont phage-encoded ankyrin-domain-containing protein, which is widely spread in phages of many host-associated contexts including human. We confirm in macrophage infection assays that the ankyrin protein (ANKp) modulates the eukaryotic host immune response against bacteria. We predict that the role of ANKp in nature is to facilitate coexistence in the tripartite interplay between phages, symbionts, and sponges and possibly many other host-microbe associations

Hologenome analysis of two marine sponges with different microbiomes

Background: Sponges (Porifera) harbor distinct microbial consortia within their mesohyl interior. We herein analysed the hologenomes of Stylissa carteri and Xestospongia testudinaria, which notably differ in their microbiome content. Results: Our analysis revealed that S. carteri has an expanded repertoire of immunological domains, specifically Scavenger Receptor Cysteine-Rich (SRCR) like domains, compared to X. testudinaria. On the microbial side, metatranscriptome analyses revealed an overrepresentation of potential symbiosis-related domains in X. testudinaria. Conclusions: Our findings provide genomic insights into the molecular mechanisms underlying host-symbiont coevolution and may serve as a roadmap for future hologenome analyses