Determinants of Microbial-Derived Dissolved Organic Matter Diversity in Antarctic Lakes.

Identifying drivers of the molecular composition of dissolved organic matter (DOM) is essential to understand the global carbon cycle, but an unambiguous interpretation of observed patterns is challenging due to the presence of confounding factors that affect the DOM composition. Here, we show, by combining ultrahigh-resolution mass spectrometry and nuclear magnetic resonance spectroscopy, that the DOM molecular composition varies considerably among 43 lakes in East Antarctica that are isolated from terrestrial inputs and human influence. The DOM composition in these lakes is primarily driven by differences in the degree of photodegradation, sulfurization, and pH.

Dissolved Organic Matter Processing in Pristine Antarctic Streams.

Accelerated glacier melt and runoff may lead to inputs of labile dissolved organic matter (DOM) to downstream ecosystems and stimulate the associated biogeochemical processes. However, still little is known about glacial DOM composition and its downstream processing before entering the ocean, although the function of DOM in food webs and ecosystems largely depends on its composition. Here, we employ a set of molecular and optical techniques (UV-vis absorption and fluorescence spectroscopy, H NMR, and ultrahigh-resolution mass spectrometry) to elucidate the composition of DOM in Antarctic glacial streams and its downstream change.

Water column gradients beneath the summer ice of a High Arctic freshwater lake as indicators of sensitivity to climate change.

Ice cover persists throughout summer over many lakes at extreme polar latitudes but is likely to become increasingly rare with ongoing climate change. Here we addressed the question of how summer ice-cover affects the underlying water column of Ward Hunt Lake, a freshwater lake in the Canadian High Arctic, with attention to its vertical gradients in limnological properties that would be disrupted by ice loss. Profiling in the deepest part of the lake under thick mid-summer ice revealed a high degree of vertical structure, with gradients in temperature, conductivity and dissolved gases.

Ammonia Oxidation Potentials and Ammonia Oxidizers of Lichen-Moss Vegetated Soils at Two Ice-free Areas in East Antarctica.

The maximum ammonia oxidation potential (AOP) of a topsoil in Langhovde, East Antarctica was 22.1±2.4‍ ‍ng N g dry soil h (2‍ ‍mM ammonium, 10°C, n=3).

Origin, distributions, and environmental significance of ubiquitous humic-like fluorophores in Antarctic lakes and streams.

This study characterized dissolved organic matter (DOM) obtained from 47 lakes and 2 streams on ice-free areas at Lützow-Holm Bay and Amundsen Bay in East Antarctica (n = 74), where few biogeochemical studies have been historically conducted. Samples were analyzed for basic water chemistry and by resin fractionation, UV-vis spectroscopy, and excitation emission matrix spectroscopy combined with parallel factor analysis (EEM-PARAFAC). Salinity of the samples ranged very broadly from fresh to hypersaline as a result of evaporative concentration.

Light quality determines primary production in nutrient-poor small lakes.

The availability of nutrients for primary producers has long been thought to be the main limiting factor for primary productivity in nutrient-poor lake ecosystems. However, recent studies have indicated that the availability of light energy is also important. On the other hand, the amount of phototroph was reported to decrease in summer in Antarctic lakes, furthermore, the light environment underwater was shown containing high amount of ultraviolet energy in small Antarctic lakes.

Mrakia hoshinonis sp. nov., a novel psychrophilic yeast isolated from a retreating glacier on Ellesmere Island in the Canadian High Arctic.

Four strains isolated from sediment sampled at the front of a retreating glacier on northern Ellesmere Island in the Canadian high Arctic, namely JCM 32575, JCM 32576, JCM 32577 and JCM 32578, belong to a novel psychrophilic basidiomycetous yeast species in the genus Mrakia. Molecular phylogenetic analysis indicated that these strains are most closely related to the type strains of Mrakia aquatica and Mrakianic combsii, but with 8-9 and 7-12 nt substitutions in ITS and in the D1/D2 domain of the LSU rRNA gene, respectively. The strains grew at sub-zero temperatures and in vitamin-free media, with lipase and cellulase highly active even at -3 °C.

Vishniacozyma ellesmerensis sp. nov., a psychrophilic yeast isolated from a retreating glacier in the Canadian High Arctic.

Two strains of a psychrophilic basidiomycetous yeast species belonging to the genus Vishniacozyma were isolated from sediments and soil at the front of a retreating glacier on northern Ellesmere Island in the Canadian Arctic. Analysis of the large subunit D1/D2 region and the internal transcribed spacer (ITS) regions of the rDNA indicated that these strains represented a novel species. The closest relatives of the novel species were Vishniacozyma globispora and V.

Seabird-affected taluses are denitrification hotspots and potential NO emitters in the High Arctic.

In High Arctic tundra ecosystems, seabird colonies create nitrogen cycling hotspots because of bird-derived labile organic matter. However, knowledge about the nitrogen cycle in such ornithocoprophilous tundra is limited. Here, we determined denitrification potentials and in-situ nitrous oxide (NO) emissions of surface soils on plant-covered taluses under piscivorous seabird cliffs at two sites (BL and ST) near Ny-Ålesund, Svalbard, in the European High Arctic.

Microbial Communities and Their Predicted Metabolic Functions in Growth Laminae of a Unique Large Conical Mat from Lake Untersee, East Antarctica.

In this study, we report the distribution of microbial taxa and their predicted metabolic functions observed in the top (U1), middle (U2), and inner (U3) decadal growth laminae of a unique large conical microbial mat from perennially ice-covered Lake Untersee of East Antarctica, using NextGen sequencing of the 16S rRNA gene and bioinformatics tools. The results showed that the U1 lamina was dominated by cyanobacteria, specifically sp., sp.

D(23)-C versus ScC@D(23)-C: Impact of Endohedral ScC Doping on Chemical Reactivity in the Photolysis of Diazirine.

We compared the chemical reactivity of D(23)-C and that of ScC@D(23)-C, both having the same carbon cage geometry, in the photolysis of 2-adamantane-2,3'-[3H]-diazirine, to clarify metal-atom doping effects on the chemical reactivity of the carbon cage. Experimental and computational studies have revealed that the chemical reactivity of the D(23)-C carbon cage is altered drastically by endohedral ScC doping. The reaction of empty D(23)-C with the diazirine under photoirradiation yields two adamantylidene (Ad) adducts.

Novel biogenic aggregation of moss gemmae on a disappearing African glacier.

Tropical regions are not well represented in glacier biology, yet many tropical glaciers are under threat of disappearance due to climate change. Here we report a novel biogenic aggregation at the terminus of a glacier in the Rwenzori Mountains, Uganda. The material was formed by uniseriate protonemal moss gemmae and protonema.

Utilizing the effective xanthophyll cycle for blooming of Ochromonas smithii and O. itoi (Chrysophyceae) on the snow surface.

Snow algae inhabit unique environments such as alpine and high latitudes, and can grow and bloom with visualizing on snow or glacier during spring-summer. The chrysophytes Ochromonas smithii and Ochromonas itoi are dominant in yellow-colored snow patches in mountainous heavy snow areas from late May to early June. It is considered to be effective utilizing the xanthophyll cycle and holding sunscreen pigments as protective system for snow algae blooming in the vulnerable environment such as low temperature and nutrients, and strong light, however the study on the photoprotection of chrysophytes snow algae has not been shown.

Stepwise functionalization of ribonucleopeptide complexes to receptors and sensors.

We describe here stepwise functionalization strategies of ribonucleopeptide complexes to receptors and sensors. A structurally well-defined complex of RNA and peptide (ribonucleopeptide: RNP) was constructed by a structure-based design. The first step optimizes an ATP-binding characteristic of an RNP receptor based on an in vitro selection of an RNP library generated by introducing randomized nucleotide sequences in the RNA subunit.

Design of sensing ribonucleopeptides for small ligands.

Here we report a simple method to convert synthetic receptors to fluorescent sensors. An RNA-peptide complex (ribonucleopeptide) with a known three-dimensional structure is used as a framework of the receptor. Artificial ribonucleopeptide sensors were created with a combination of in vitro selection method and successive modification of the peptide with a fluorophore.

Sympathetic neural regulation of heart rate is robust against high plasma catecholamines.

The sympathetic regulation of heart rate (HR) may be attained by neural and humoral factors. With respect to the humoral factor, plasma noradrenaline (NA) and adrenaline (Adr) can reportedly increase to levels approximately 10 times higher than resting level during severe exercise. Whether such high plasma NA or Adr interfered with the sympathetic neural regulation of HR remained unknown.

Stepwise molding of a highly selective ribonucleopeptide receptor.

The structural characteristics of RNA-peptide (RNP) complexes are suitable for molding of a ligand-binding pocket of the RNP complex in a stepwise manner. The first step involves molding of the RNA subunit by in vitro selection of an RNP pool originating from an RNA library and the peptide, as previously reported for the construction of an ATP-binding RNP complex from an RRE RNA-Rev peptide complex. The second step involves selection from an RNP library consisting of Rev peptides with randomized amino acid residues and the RNA subunit selected in the first molding.