Ebriid phylogeny and the expansion of the Cercozoa

Ebria tripartita is a phagotrophic flagellate present in marine coastal plankton communities worldwide. This is one of two (possibly four) described extant species in the Ebridea, an enigmatic group of eukaryotes with an unclear phylogenetic position. Ebriids have never been cultured, are usually encountered in low abundance and have a peculiar combination of ultrastructural characters including a large nucleus with permanently condensed chromosomes and an internal skeleton composed of siliceous rods. Consequently, the taxonomic history of the group has been tumultuous and has included a variety of affiliations, such as silicoflagellates, dinoflagellates, 'radiolarians' and 'neomonads'. Today, the Ebridea is treated as a eukaryotic taxon incertae sedis because no morphological or molecular features have been recognized that definitively relate ebriids with any other eukaryotic lineage. We conducted phylogenetic analyses of small subunit rDNA sequences from two multi-specimen isolations of Ebria tripartita. The closest relatives to the sequences from Ebria tripartita are environmental sequences from a submarine caldera floor. This newly recognized Ebria clade was most closely related to sequences from described species of Cryothecomonas and Protaspis. These molecular phylogenetic relationships were consistent with current ultrastructural data from all three genera, leading to a robust placement of ebriids within the Cercozoa.     

基于MaxEnt模型模拟肯尼亚茜草科河骨木属植物的潜在分布及其在植物志中的应用初探

物种分布模型目前被广泛应用于生物学、生态学和保护生物学的各个领域。该文以肯尼亚茜草科河骨木属（Afrocanthium ）为例,利用最大熵模型（MaxEnt）模拟植物在当前气候情景下的潜在分布,并将这些分布图利用于正在编写的《肯尼亚植物志》中。结果显示,基于足够的原始标本记录,模型能够很好地模拟出每种植物的潜在分布区域。相比传统和新一代植物志仅提供标本信息点或是粗略分布图,《肯尼亚植物志》预采用的潜在分布图,将为志书使用者提供更加全面、实用的信息。     

Hemorrhagic fever of bunyavirus etiology: disease models and progress towards new therapies

A growing number of bunyaviruses are known to cause viral hemorrhagic fever (VHF), a severe febrile illness which can progress to hypovolemic shock and multi-organ failure and is characterized by hematologic abnormalities and vascular leak. At present, there are no approved vaccines or antiviral therapies to effectively prevent or treat VHF caused by pathogenic bunyaviruses. Advances in the modeling of bunyaviral infections have facilitated efforts towards the development of novel post-exposure prophylactic and therapeutic countermeasures, several of which may some day be approved for human use. Here, we review recent progress in animal models of severe bunyaviral infections essential to this mission, as well as promising antivirals and biologicals that are at various stages of the development process.     

Temporary vs. Permanent Sub-slab Ports: A Comparative Performance Study

Vapor intrusion (VI) is the migration of subsurface vapors, including radon and volatile organic compounds (VOCs), from the subsurface to indoor air. The VI exposure pathway extends from the contaminant source, which can be impacted soil or groundwater, to indoor air-exposure points. VOC contaminants of concern typically include halogenated solvents as well as petroleum hydrocarbons. Radon, a colorless radioactive gas that is released by radioactive decay of radionuclides in rock and soil, migrates into homes through VI in a similar fashion to VOCs. This project focused on the performance of permanent versus temporary sub-slab sampling ports for the determination of VI of halogenated VOCs and radon into an unoccupied house. VOC and radon concentrations measured simultaneously in soil gas using collocated temporary and permanent ports appeared to be independent of the type of port. The variability between collocated temporary and permanent ports was much less than the spatial variability between different locations within a single residential duplex. Post sampling leak test results suggested that the temporary SSP desiccation and cracking of the clay portion of the seal were not as detrimental to the port seal performance as would have been expected, this suggests that the Teflon tape portion of the seals served an important function. Pre and post sampling leak tests are advisable when temporary ports are used to collect a time-integrated sample. These results suggest that temporary sub-slab sampling ports can provide data equivalent to that collected from a permanent sub-slab sampling port.     

Chemical rescue of proton transfer in catalysis by carbonic anhydrases in the beta- and gamma-class

Catalysis of the dehydration of HCO(3)(-) by carbonic anhydrase requires proton transfer from solution to the zinc-bound hydroxide. Carbonic anhydrases in each of the alpha, beta, and gamma classes, examples of convergent evolution, appear to have a side chain extending into the active site cavity that acts as a proton shuttle to facilitate this proton transfer, with His 64 being the most prominent example in the alpha class. We have investigated chemical rescue of mutants in two of these classes in which a proton shuttle has been replaced with a residue that does not transfer protons: H216N carbonic anhydrase from Arabidopsis thaliana (beta class) and E84A carbonic anhydrase from the archeon Methanosarcina thermophila (gamma class). A series of structurally homologous imidazole and pyridine buffers were used as proton acceptors in the activation of CO(2) hydration at steady state and as proton donors of the exchange of (18)O between CO(2) and water at chemical equilibrium. Free energy plots of the rate constants for this intermolecular proton transfer as a function of the difference in pK(a) of donor and acceptor showed extensive curvature, indicating a small intrinsic kinetic barrier for the proton transfers. Application of Marcus rate theory allowed quantitative estimates of the intrinsic kinetic barrier which were near 0.3 kcal/mol with work functions in the range of 7-11 kcal/mol for mutants in the beta and gamma class, similar to results obtained for mutants of carbonic anhydrase in the alpha class. The low values of the intrinsic kinetic barrier for all three classes of carbonic anhydrase reflect proton transfer processes that are consistent with a model of very rapid proton transfer through a flexible matrix of hydrogen-bonded solvent structures sequestered within the active sites of the carbonic anhydrases.     

JET‐SUSPENDED,CALCITE‐BALLASTED CYANOBACTERIAL WATERWARTS IN A DESERT SPRING1

We describe a population of colonial cyanobacteria (waterwarts) that develops as the dominant primary producer in a bottom‐fed, O₂‐poor, warm spring in the Cuatro Ciénegas karstic region of the Mexican Chihuahuan Desert. The centimeter‐sized waterwarts were suspended within a central, conically shaped, 6‐m deep well by upwelling waters. Waterwarts were built by an Aphanothece‐like unicellular cyanobacterium and supported a community of epiphytic filamentous cyanobacteria and diatoms but were free of heterotrophic bacteria inside. Sequence analysis of 16S rRNA genes revealed that this cyanobacterium is only distantly related to several strains of other unicellular cyanobacteria (Merismopedia, Cyanothece, Microcystis). Waterwarts contained orderly arrangements of mineral crystallites, made up of microcrystalline low‐magnesium calcite with high levels of strontium and sulfur. Waterwarts were 95.9% (v/v) glycan, 2.8% cells, and 1.3% mineral grains and had a buoyant density of 1.034 kg·L^?1. An analysis of the hydrological properties of the spring well and the waterwarts demonstrated that both large colony size and the presence of controlled amounts of mineral ballast are required to prevent the population from being washed out of the well. The unique hydrological characteristics of the spring have likely selected for both traits. The mechanisms by which controlled nucleation of extracellular calcite is achieved remain to be explored.     

Noninvasive evaluation of liver metabolism by 2H and 13C NMR isotopomer analysis of human urine

Mammalian liver disposes of acetaminophen and other ingested xenobiotics by forming soluble glucuronides that are subsequently removed via renal filtration. When given in combination with the stable isotopes 2H and 13C, the glucuronide of acetaminophen isolated from urine provides a convenient "chemical biopsy" for evaluating intermediary metabolism in the liver. Here, we describe isolation and purification of urinary acetaminophen glucuronide and its conversion to monoacetone glucose (MAG). Subsequent 2H and 13C NMR analysis of MAG from normal volunteers after ingestion of 2H2O and [U-13C3]propionate allowed a noninvasive profiling of hepatic gluconeogenic pathways. The method should find use in metabolic studies of infants and other populations where blood sampling is either limited or problematic.