The intestinal microbiota is known to regulate host energy homeostasis and can be influenced by highcalorie diets. However, changes affecting the ecosystem at the functional level are still not well characterized. We measured shifts in cecal bacterial communities in mice fed a carbohydrate or high-fat (HF) diet for 12 weeks at the level of the following: (i) diversity and taxa distribution by high-throughput 16S ribosomal RNA gene sequencing; (ii) bulk and single-cell chemical composition by Fourier-transform infrared-(FT-IR) and Raman micro-spectroscopy and (iii) metaproteome and metabolome via highresolution mass spectrometry. High-fat diet caused shifts in the diversity of dominant gut bacteria and altered the proportion of Ruminococcaceae (decrease) and Rikenellaceae (increase). FT-IR spectroscopy revealed that the impact of the diet on cecal chemical fingerprints is greater than the impact of microbiota composition. Diet-driven changes in biochemical fingerprints of members of the Bacteroidales and Lachnospiraceae were also observed at the level of single cells, indicating that there were distinct differences in cellular composition of dominant phylotypes under different diets. Metaproteome and metabolome analyses based on the occurrence of 1760 bacterial proteins and 86 annotated metabolites revealed distinct HF diet-specific profiles. Alteration of hormonal and anti-microbial networks, bile acid and bilirubin metabolism and shifts towards amino acid and simple sugars metabolism were observed. We conclude that a HF diet markedly affects the gut bacterial ecosystem at the functional level.

The cohort of the ammonia-oxidizing archaea (AOA) of the phylum Thaumarchaeota is a diverse, widespread and functionally important group of microorganisms in many ecosystems. However, our understanding of their biology is still very rudimentary in part because all available genome sequences of this phylum are from members of the Nitrosopumilus cluster. Here we report on the complete genome sequence of Candidatus Nitrososphaera gargensis obtained from an enrichment culture, representing a different evolutionary lineage of AOA frequently found in high numbers in many terrestrial environments. With its 2.83 Mb the genome is much larger than that of other AOA. The presence of a high number of (active) IS elements/transposases, genomic islands, gene duplications and a complete CRISPR/Cas defence system testifies to its dynamic evolution consistent with low degree of synteny with other thaumarchaeal genomes. As expected, the repertoire of conserved enzymes proposed to be required for archaeal ammonia oxidation is encoded by N. gargensis, but it can also use urea and possibly cyanate as alternative ammonia sources. Furthermore, its carbon metabolism is more flexible at the central pyruvate switch point, encompasses the ability to take up small organic compounds and might even include an oxidative pentose phosphate pathway. Furthermore, we show that thaumarchaeota produce cofactor F420 as well as polyhydroxyalkanoates. Lateral gene transfer from bacteria and euryarchaeota has contributed to the metabolic versatility of N. gargensis. This organisms is well adapted to its niche in a heavy metal-containing thermal spring by encoding a multitude of heavy metal resistance genes, chaperones and mannosylglycerate as compatible solute and has the genetic ability to respond to environmental changes by signal transduction via a large number of two-component systems, by chemotaxis and flagella-mediated motility and possibly even by gas vacuole formation. These findings extend our understanding of thaumarchaeal evolution and physiology and offer many testable hypotheses for future experimental research on these nitrifiers.

The Ricci flow was introduced by Hamilton in 1982 [H1] in order to prove that a compact three-manifold admitting a Riemannian metric of positive Ricci curvature is a spherical space form. In dimension four Hamilton showed that compact four-manifolds with positive curvature operators are spherical space forms as well [H2]. More generally, the same conclusion holds for compact four-manifolds with 2-positive curvature operators [Che]. Recall that a curvature operator is called 2-positive, if the sum of its two smallest eigenvalues is positive. In arbitrary dimensions Huisken [Hu] described an explicit open cone in the space of curvature operators such that the normalized Ricci flow evolves metrics whose curvature operators are contained in that cone into metrics of constant positive sectional curvature.Hamilton conjectured that in all dimensions compact Riemannian manifolds with positive curvature operators must be space forms. In this paper we confirm this conjecture. More generally, we show the following Theorem 1. On a compact manifold the normalized Ricci flow evolves a Riemannian metric with 2-positive curvature operator to a limit metric with constant sectional curvature. The theorem is known in dimensions below five [H3], [H1], [Che]. Our proof works in dimensions above two: we only use Hamilton's maximum principle and Klingenberg's injectivity radius estimate for quarter pinched manifolds. Since in dimensions above two a quarter pinched orbifold is covered by a manifold (see Proposition 5.2), our proof carries over to orbifolds. This is no longer true in dimension two. In the manifold case it is known that the normalized Ricci flow converges to a metric of constant curvature for any initial metric [H3], [Cho]. However, there exist two-dimensional orbifolds with positive sectional curvature which are not covered by a manifold. On such orbifolds the Ricci flow converges to a nontrivial Ricci soliton [CW].

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Trabeculae significantly affect quantifications of LV volume and mass. The superior reproducibility of LV measurements with the inclusion of endocardial trabeculae in the cavity volume favors this tracing algorithm for clinical use.