Taxonomic Dependency of Beta Diversity for Bacteria, Archaea and Fungi in a Semi-Arid Lake

Microbial beta diversity has been recently studied along the water depth in aquatic ecosystems, however its turnover and nestedness components remain elusive especially for multiple taxonomic groups. Based on the beta diversity partitioning developed by Baselga and Local Contributions to Beta Diversity (LCBD) partitioning by Legendre, we examined the water-depth variations in beta diversity components of bacteria, archaea and fungi in surface sediments of Hulun Lake, a semi-arid lake in northern China, and further explored the relative importance of environmental drivers underlying their patterns. We found that the relative abundances of Proteobacteria, Chloroflexi, Euryarchaeota and Rozellomycota increased towards deep water, while Acidobacteria, Parvarchaeota and Chytridiomycota decreased. For bacteria and archaea, there were significant (P < 0.05) decreasing water-depth patterns for LCBD and LCBDRepl (i.e., species replacement), while increasing patterns for total beta diversity and turnover, implying that total beta diversity and LCBD were dominated by species turnover or LCBDRepl. Further, bacteria showed a strong correlation with archaea regarding LCBD, total beta diversity and turnover. Such parallel patterns among bacteria and archaea were underpinned by similar ecological processes like environmental selection. Total beta diversity and turnover were largely affected by sediment total nitrogen, while LCBD and LCBDRepl were mainly constrained by water NO2−-N and NO3−-N. For fungal community variation, no significant patterns were observed, which may be due to different drivers like water nitrogen or phosphorus. Taken together, our findings provide compelling evidences for disentangling the underlying mechanisms of community variation in multiple aquatic microbial taxonomic groups.

Invasive grass causes biotic homogenization in wetland birds

Plant invasions often lead to homogenization of the plant community, but the potential for plant invasions to cause homogenization of other trophic levels is under-studied in many systems. We tested whether the bird community in Phragmites australis-invaded marsh would exhibit spatial and temporal taxonomic homogenization compared to remnant cattail and meadow marsh. We compared the bird community using marsh invaded by P. australis and remnant, uninvaded marsh vegetation in a year with average water depths and a year with above-average water depths in the coastal marshes of a World Biosphere Reserve. Our results demonstrate strong evidence for spatial and temporal homogenization of the wetland bird community following P. australis invasion. The birds present in P. australis-invaded marsh were a nested subset of those present in remnant marsh, and total beta diversity decreased when water depths were above average. In contrast, total beta diversity was high in remnant marsh vegetation and stable between the two years. The distinctively structured vegetation zones in remnant (uninvaded) marsh yields structural complexity and habitat heterogeneity that supports greater taxonomic turnover in the bird community. Our study provides evidence that invasion by a plant has resulted in biological homogenization of the wetland bird community.

Arbuscular mycorrhizal trees influence the latitudinal beta-diversity gradient of tree communities in forests worldwide

Arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) associations are critical for host-tree performance. However, how mycorrhizal associations correlate with the latitudinal tree beta-diversity remains untested. Using a global dataset of 45 forest plots representing 2,804,270 trees across 3840 species, we test how AM and EcM trees contribute to total beta-diversity and its components (turnover and nestedness) of all trees. We find AM rather than EcM trees predominantly contribute to decreasing total beta-diversity and turnover and increasing nestedness with increasing latitude, probably because wide distributions of EcM trees do not generate strong compositional differences among localities. Environmental variables, especially temperature and precipitation, are strongly correlated with beta-diversity patterns for both AM trees and all trees rather than EcM trees. Results support our hypotheses that latitudinal beta-diversity patterns and environmental effects on these patterns are highly dependent on mycorrhizal types. Our findings highlight the importance of AM-dominated forests for conserving global forest biodiversity.

ACTIN CYTOSKELETON ORGANIZATION IN OOCYTES AT VARIOUS STAGES OF DROSOPHILA MELANOGASTER OOGENESIS AFTER EXPOSURE IN A MICROGRAVITY SIMULATOR OVER THE COMPLETE GAMETOGENESIS CYCLE

The paper deals with the effects of modeled microgravity on actin cytoskeleton in oocytes at various stages of Drosophila melanogaster oogenesis over the complete gametogenesis cycle. Total actin content and F-actin singly was determined using immunohistochemical analysis. The results point to the growth of both total beta-actin and its polymer recognized by phalloidin. This finding can have key implications for evaluation of risks for the reproductive potential from the spaceflight factors.

Radioactivity of Bottled Water from Trade Network in Kyiv

In 2018-2019, we examined the radioactivity of 40 samples of bottled water of popular brands produced both in Ukraine and abroad, which were purchased in one Kyiv supermarket. The first stage of the study provided for the identification of total alpha and total beta activities. In the case of excessing their regulated values, we proceeded to the determination of the content of radium-226 and natural mixture of uranium isotopes. The study results evidenced that total alpha and total beta activities of low mineralization water do not exceed the regulated values. Total alpha activity exceeded the regulated value of 0.1 Bq/l ten times in specific cases and total beta-activity exceeded the value of 1.0 Bq/l almost three times for the majority of high mineralization water brands. The results of measuring total alpha and total beta activities depending on time elapsed from the moment the sample was prepared to the start of the measurements showed an increase in the alpha activity over time is typical for individual water samples, which indicates the accumulation of radioactivity from radium-226 decay products. However, the results of measuring the activity of radium-226 and a natural mixture of uranium isotopes did not reveal cases of exceeding regulated levels, which allows considering water of all brands suitable in terms of radionuclide content. Assessment of radiation doses from consumption of bottled water containing the measured values of radium-226 and natural mixture of uranium isotopes did not reveal exceeding regulated value of 0.1 mSv/year. Only one bottled water brand was an exception, since the estimated radiation dose for it was 0.2 mSv/year for the category of children aged 12 to 17 years with 98 % of its value due to radium-226. Such a radiation dose value was received assuming an annual consumption of 1.5 liters per day.

Total Synthesis of Tiacumicin B: Study of the Challenging β-Selective Glycosylations

<div>We report here a full account of the total synthesis of tiacumicin B (Tcn-B), a natural glycosylated macrolide with remarkable antibiotic properties. Our strategy is based on our experience with the synthesis of the tiacumicin B aglycone and on unique 1,2-<i>cis</i>-glycosylation steps. It features the conclusive use of sulfoxide anomeric leaving-groups in combination with a remote 3-<i>O</i>-picoloyl group on the donors allowing highly beta-selective rhamnosylation and noviosylation that rely on H-bond-mediated Aglycone Delivery (HAD). The rhamnosylated C1-C3 fragment was anchored to the C4-C19 aglycone fragment by a Suzuki-Miyaura cross-coupling. Ring-size selective Shiina macrolactonization provided a semi-glycosylated aglycone that was engaged directly in the noviosylation step with a virtually total beta-selectivity. Finally, a novel deprotection method was devised for the removal of a 2-naphthylmethylidene (Nap) ether on a phenol and efficient removal of all the protecting groups provided synthetic tiacumicin B.<br></div><div> </div>

Total Synthesis of Tiacumicin B: Study of the Challenging β-Selective Glycosylations

<div>We report here a full account of the total synthesis of tiacumicin B (Tcn-B), a natural glycosylated macrolide with remarkable antibiotic properties. Our strategy is based on our experience with the synthesis of the tiacumicin B aglycone and on unique 1,2-<i>cis</i>-glycosylation steps. It features the conclusive use of sulfoxide anomeric leaving-groups in combination with a remote 3-<i>O</i>-picoloyl group on the donors allowing highly beta-selective rhamnosylation and noviosylation that rely on H-bond-mediated Aglycone Delivery (HAD). The rhamnosylated C1-C3 fragment was anchored to the C4-C19 aglycone fragment by a Suzuki-Miyaura cross-coupling. Ring-size selective Shiina macrolactonization provided a semi-glycosylated aglycone that was engaged directly in the noviosylation step with a virtually total beta-selectivity. Finally, a novel deprotection method was devised for the removal of a 2-naphthylmethylidene (Nap) ether on a phenol and efficient removal of all the protecting groups provided synthetic tiacumicin B.<br></div><div> </div>

Total Synthesis of Tiacumicin B: Study of the Challenging β-Selective Glycosylations

<div>We report here a full account of the total synthesis of tiacumicin B (Tcn-B), a natural glycosylated macrolide with remarkable antibiotic properties. Our strategy is based on our experience with the synthesis of the tiacumicin B aglycone and on unique 1,2-<i>cis</i>-glycosylation steps. It features the conclusive use of sulfoxide anomeric leaving-groups in combination with a remote 3-<i>O</i>-picoloyl group on the donors allowing highly beta-selective rhamnosylation and noviosylation that rely on H-bond-mediated Aglycone Delivery (HAD). The rhamnosylated C1-C3 fragment was anchored to the C4-C19 aglycone fragment by a Suzuki-Miyaura cross-coupling. Ring-size selective Shiina macrolactonization provided a semi-glycosylated aglycone that was engaged directly in the noviosylation step with a virtually total beta-selectivity. Finally, a novel deprotection method was devised for the removal of a 2-naphthylmethylidene (Nap) ether on a phenol and efficient removal of all the protecting groups provided synthetic tiacumicin B.<br></div><div> </div>

Total Beta—Where Does It Fit in Valuation Theory

The valuation of any company by the discounted cash flow method is divided into two different tasks: forecasting cash flows and discounting these same cash flows using the appropriate discount rate. The latter requires a good understanding of the risks faced by the subject company's cash flows to be able to determine the appropriate risk premia to compensate a typical willing buyer and satisfy a typical willing seller. There is a high level of ambiguity and dispersion of opinions about how to quantify these risks especially when valuing closely held companies. To avoid dealing with the task of identifying and measuring components of the appropriate risk premia for the subject company, some practitioners have turned to a measure that, supposedly, lumps all risks together (which they term Total Beta) and purportedly then allows one to estimate a total cost of equity. The proponents of total beta believe that by using a “total risk” beta there is no need to consider size premia, lack of marketability premia or company specific risk premia. Critics of total beta argue that there is no theoretical basis for total beta as a measure of total risk. This paper argues for the camp of the critics of total beta because we believe it represents a major departure from finance theory and does not adjust the cost of capital correctly for Company Specific Risk. Then, we examine academic research to show that the two major arguments used by total beta proponents to discredit the existing model do not hold. We do not argue that the existing models are absolute truth. We recognize the limitation of the CAPM and/or Modified CAPM models and we admit their inability of answer all questions regarding the cost of equity. However, we believe that total beta is not a step in the right direction.