Ecology impacts the decrease of Spirochaetes and Prevotella in the fecal gut microbiota of urban humans

Compared to the huge microbial diversity in most mammals, human gut microbiomes have lost diversity while becoming specialized for animal-based diets - especially compared to chimps, their genetically closest ancestors. The lowered microbial diversity within the gut of westernized populations has also been associated with different kinds of chronic inflammatory diseases in humans. To further deepen our knowledge on phylogenetic and ecologic impacts on human health and fitness, we established the herein presented biobank as well as its comprehensive microbiota analysis. In total, 368 stool samples from 38 different animal species, including Homo sapiens, belonging to four diverse mammalian orders were collected at seven different locations and analyzed by 16S rRNA gene amplicon sequencing. Comprehensive data analysis was performed to (i) determine the overall impact of host phylogeny vs. diet, location, and ecology and to (ii) examine the general pattern of fecal bacterial diversity across captive mammals and humans.By using a controlled study design with captive mammals we could verify that host phylogeny is the most dominant driver of mammalian gut microbiota composition. However, the effect of ecology appears to be able to overcome host phylogeny and should therefore be studied in more detail in future studies. Most importantly, our study could observe a remarkable decrease of Spirochaetes and Prevotella in westernized humans and platyrrhines, which is probably not only due to diet, but also to the social behavior and structure in these communities.Our study highlights the importance of phylogenetic relationship and ecology within the evolution of mammalian fecal microbiota composition. Particularly, the observed decrease of Spirochaetes and Prevotella in westernized communities might be associated to lifestyle dependent rapid evolutionary changes, potentially involved in the establishment of dysbiotic microbiomes, which promote the etiology of chronic diseases

Supramolecular networks stabilise and functionalise black phosphorus

The limited stability of the surface of black phosphorus (BP) under atmospheric conditions is a significant constraint on the exploitation of this layered material and its few layer analogue, phosphorene, as an optoelectronic material. Here we show that supramolecular networks stabilised by hydrogen bonding can be formed on BP, and that these monolayer-thick films can passivate the BP surface and inhibit oxidation under ambient conditions. The supramolecular layers are formed by solution deposition and we use atomic force microscopy to obtain images of the BP surface and hexagonal supramolecular networks of trimesic acid and melamine cyanurate (CA.M) under ambient conditions. The CA.M network is aligned with rows of phosphorus atoms and forms large domains which passivate the BP surface for more than a month, and also provides a stable supramolecular platform for the sequential deposition of 1,2,4,5-tetrakis(4-carboxyphenyl)benzene to form supramolecular heterostructures

Micrometre-long covalent organic fibres by photoinitiated chain-growth radical polymerization on an alkali-halide surface

On-surface polymerization is a promising technique to prepare organic functional nanomaterials that are challenging to synthesize in solution, but it is typically used on metal substrates, which play a catalytic role. Previous examples on insulating surfaces have involved intermediate self-assembled structures, which face high barriers to diffusion, or annealing to higher temperatures, which generally causes rapid dewetting and desorption of the monomers. Here we report the photoinitiated radical polymerization, initiated from a two-dimensional gas phase, of a dimaleimide monomer on an insulating KCl surface. Polymer fibres up to 1 μm long are formed through chain-like rather than step-like growth. Interactions between potassium cations and the dimaleimide’s oxygen atoms facilitate the propagation of the polymer fibres along a preferred axis of the substrate over long distances. Density functional theory calculations, non-contact atomic force microscopy imaging and manipulations at room temperature were used to explore the initiation and propagation processes, as well as the structure and stability of the resulting one-dimensional polymer fibres

Absolute step and kink formation energies of Pb derived from step roughening of two-dimensional islands and facets

The shapes of (111) oriented two-dimensional (2D) islands and facets, the latter being part of three-dimensional (3D) crystallites of Pb, were equilibrated at 104-520 K. Island sizes were in the range of 15-90 nm radius, facets typically at 100-270 nm radius. They were imaged by scanning tunneling microscopy to provide the exact outline of the bounding step. Increased step roughening with increasing temperature decreases the radius anisotropy of islands and facets in a consistent manner. Products of island/facet radius times local step curvature versus temperature were obtained experimentally, serving as the basis of absolute step and kink energies at 0 K. They are f(1A)(0)=128.3+/-0.3 meV, f(1B)(0)=115.7+/-5.8 meV, and epsilon(kA)=42.5+/-1.0 meV, epsilon(kB)=60.6+/-1.6 meV, respectively. The combination of studying small 2D islands (unstable at high temperature) and large 2D facets allows measurements over a very large range of temperatures

Absolute surface free energies of Pb

Three-dimensional (3D) equilibrium crystal shapes (ECS) of Pb are utilized for the first time to determine absolute surface free energies via a quantitative evaluation of the measured ECS and published values of step free energies of vicinal (1 1 1) surfaces. 3D images of Pb crystallites are obtained by scanning tunneling microscopy at 323-393 K. Line scans through high symmetry azimuths are transformed into an anisotropic relative surface free energy, gamma(theta, T). The absolute surface free energy of Pb(1 1 1) is obtained from the limiting slopes, df(theta, T)/d tan theta, of the orientation dependent f(theta, T) gamma(theta, T)/ cos theta at the boundaries of the (1 1 1) facet, located at theta = 0degrees. This value is 25.7 +/- 1.4 meV/Angstrom(2) or 440 +/- 22 mJ/m(2). Absolute surface free energies of other low-index orientations, such as (1 0 0), (1 1 0) etc. are calculated from the relative anisotropy of gamma(theta)/gamma(1 1 1). It is found that surface free energies of orientation (h k l), expressed in meV/atom, scale with the number of bonds broken in forming such a surface. Free energies of steps bounding other facets, such as (1 0 0), (1 1 0), (1 1 2), (1 1 3) and (2 2 1), are evaluated in the [0 1 (1) over bar] zone, using the corresponding facet radii and the absolute surface free energies of those facets. (C) 2002 Published by Elsevier Science B.V

Universal exponents and step-step interactions on vicinal Pb(111) surfaces

A 1 mum diameter Pb crystallite, supported on Ru(001), was equilibrated and imaged by scanning tunneling microscopy at 298 K. The vicinal shapes close to the (111) facet at the top of the crystal were analyzed in detail to determine the critical shape exponent and the step-step interaction energy as well as the interaction constant of the potential. An average shape exponent of 1.47 and a step interaction energy of similar to32 meV/Angstrom(2) were obtained. The exponent is very close to the theoretically predicted universal value of 3/2 and as such provides clear evidence for a dominant 1/x(2) step interaction potential. The ratio of step free energy to step interaction energy for Pb at 298 K is similar to0.34