The biomass of fungal mycelium in buried paleosols and surface soils of the steppe zone

The contents of fungal mycelium have been studied in paleosols of ancient archeological monuments and in surface soils within the steppe, dry steppe, and desert zones of European Russia, on the Stavropol, Privolzhskaya, and Ergeni uplands. The buried paleosols date back to the Bronze Age (4600–4500 and 4000–3900 BP), the Early Iron Age (1900–1800 BP), and the early 18th century (1719–1721). The fungal mycelium has been found in all these paleosols. The biomass of fungal mycelium varies from 2 to 124 μg/g of soil. The distribution patterns of fungal mycelium in the profiles of buried paleosols and surface soils have been identified. It is shown that the dark-colored mycelium is typical of the ancient paleosols. In some cases, the content of the dark-colored mycelium in them may reach 100% of the total mycelium biomass.     

A B-cell targeting virus disrupts potentially protective genomic methylation patterns in lymphoid tissue by increasing global 5-hydroxymethylcytosine levels

The mechanisms by which viruses modulate the immune system include changes in host genomic methylation. 5-hydroxymethylcytosine (5hmC) is the catalytic product of the Tet (Ten-11 translocation) family of enzymes and may serve as an intermediate of DNA demethylation. Recent reports suggest that 5hmC may confer consequences on cellular events including the pathogenesis of disease; in order to explore this possibility further we investigated both 5-methylcytosine (5mC) and 5hmC levels in healthy and diseased chicken bursas of Fabricius. We discovered that embryonic B-cells have high 5mC content while 5hmC decreases during bursa development. We propose that a high 5mC level protects from the mutagenic activity of the B-cell antibody diversifying enzyme activation induced deaminase (AID). In support of this view, AID mRNA increases significantly within the developing bursa from embryonic to post hatch stages while mRNAs that encode Tet family members 1 and 2 reduce over the same period. Moreover, our data revealed that infectious bursal disease virus (IBDV) disrupts this genomic methylation pattern causing a global increase in 5hmC levels in a mechanism that may involve increased Tet 1 and 2 mRNAs. To our knowledge this is the first time that a viral infection has been observed to cause global increases in genomic 5hmC within infected host tissues, underlining a mechanism that may involve the induction of B-cell genomic instability and cell death to facilitate viral egress.     

Characterization of mammalian selenoproteomes

In the genetic code, UGA serves as a stop signal and a selenocysteine codon, but no computational methods for identifying its coding function are available. Consequently, most selenoprotein genes are misannotated. We identified selenoprotein genes in sequenced mammalian genomes by methods that rely on identification of selenocysteine insertion RNA structures, the coding potential of UGA codons, and the presence of cysteine-containing homologs. The human selenoproteome consists of 25 selenoproteins.     

Mitosis through the microscope: advances in seeing inside live dividing cells

The most visually spectacular events in the life of a cell occur when it divides. This is especially true in higher eukaryotes, where the size and geometry of cells allow the division process to be followed through a microscope with considerable clarity. In these organisms, the membrane surrounding the nucleus breaks down after the replicated DNA has condensed to form discrete chromosomes. Several new structures are then assembled to separate the chromosomes and partition the cytoplasm into two separate cells.     

PAMELA measurements of cosmic-ray proton and helium spectra

Protons and helium nuclei are the most abundant components of the cosmic radiation. Precise measurements of their fluxes are needed to understand the acceleration and subsequent propagation of cosmic rays in our Galaxy. We report precision measurements of the proton and helium spectra in the rigidity range 1 gigavolt to 1.2 teravolts performed by the satellite-borne experiment PAMELA (payload for antimatter matter exploration and light-nuclei astrophysics). We find that the spectral shapes of these two species are different and cannot be described well by a single power law. These data challenge the current paradigm of cosmic-ray acceleration in supernova remnants followed by diffusive propagation in the Galaxy. More complex processes of acceleration and propagation of cosmic rays are required to explain the spectral structures observed in our data.     

Effect of mycorhiza-forming fungus <Emphasis Type="Italic">Glomus intraradices</Emphasis> on phytoextraction of nickel and copper and status of microbe cenoses under conditions of a model experiment

Effect of inoculation of plants by mycorhiza-forming fungus Glomus intraradices on nickel and copper phytoextraction from soddy-podzolic soil has been studied. The soil was intentionally contaminated by these elements. Mycorhization may cause both a rise and a drop in the content of the elements in the above ground parts of plants. It is shown that inoculation of plants by mycorhiza-forming fungus by its application to the soil at seeding does not result in the destabilization of microbe cenoses in the variants with application of heavy metals and in control variants.     

Modifications of the mineralogical composition and surface properties of soils as related to steppe climate dynamics in historical time

This work presents the results of a study of changes in the soil mineral components and the related modifications of the chemical composition and surface properties of soils in the desert-steppe zone in the southern part of the Ergeni Upland. Burial mounds dating back to the Bronze epoch have been investigated. According to radiocarbon data, their ages are estimated at 5100 ± 50, 4410 ± 100, 4260 ± 120, 4120 ± 70, and 3960 ± 40 years. The substantial transformation of the clay minerals, the molar chemical coefficients, the magnetic mineralogy, and the surface properties of the soils permits us to assess the rates of the mineralogical transformations caused by the climate change during the time interval of less than <∼100 years. The ratio between the content of the mineral phases in the buried soils of different ages testifies to the primary importance of climatic factor in comparison with the total duration of weathering or the soil existence on the land surface prior to its burial, i.e., the soil age.     

Changes in the Structural State of Soils in the Lower Volga Region during the Past 3500 Years as Related to Climate Fluctuations

The structural state of modern and buried chestnut soils on the Privolzhskaya Upland (Volgograd oblast) was studied in order to determine changes in the soil structure in dependence on the time of soil burying. The soils buried 3500, 1700, and 700 years ago and modern background chestnut soils were examined. The structural state of soils was determined via their fractionation on a set of sieves (10–0.25 mm) in the air-dry state. We determined the contents of coarse aggregates, total aggregates, disperse soil matter, aggregation coefficient, and the degree of differentiation of the soil profiles. It was found that the structure of buried soils is preserved for 3500 years after the soil burying. The structural state of the studied soils changed with time depending on the climatic conditions that existed at the moment of soil burying. In humid periods, the amount of coarse aggregates (lumps) decreased, and the content of aggregated fractions increased; the reverse processes took place in arid epochs. Thus, it was shown that the aggregate composition of soils is specific for each period of soil formation and depends on the degree of climatic humidity. It is preserved in the buried soils independently on the duration of their existence in the buried state. We determined the impact of aggregate size on the C_org tolerance toward mineralization processes. It was shown that the content of organic carbon and its physical protection from mineralization are determined by different mechanisms of its fixing in aggregates of different sizes and depend on the conditions for the development of soil structure before burying and on the duration of the soil existence in the buried state. The results obtained in this study can be used as a retrospective basis for predicting changes in the physical properties of soils under conditions of changing climate.