Browsing by Autor "Sergio Rubin"

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Aulacoseira kruegeriana (Diatomeae, Coscinodiscophyceae): a new centric diatom from high-elevation Andean rivers and streams of Bolivia
(Taylor & Francis, 2015) Eduardo A. Morales; Sinziana F. Rivera; Sergio Rubin; Morgan L. Vis; Václav Houk
A new centric diatom, Aulacoseira kruegeriana sp. nov., collected from small streams in the Yungas (cloud forest) region of Bolivia, is described based on light and electron microscopy. The new species is morphologically similar to Aulacoseira principissa Van de Vijver, A. alpigena (Grunow) Krammer, A. ambigua (Grunow) Simonsen, A. gessneri (Hustedt) Simonsen, A. laevissima (Grunow in Van Heurck) Krammer, A. lirata (Ehrenberg) Ross, and A. nygaardii (Camburn) Camburn & D.F. Charles. However, it is distinguished by its finer frustule structure, presence and features of separation and linking spines, density of areolae, rotae as mostly three-point bars, a solid and thick ringleist and indistinctly sigmoid mantle striae. Aulacoseira kruegeriana is the first new species of Aulacoseira. Thwaites reported from Bolivia. However, the literature on centric diatoms in this country is currently scarce and, as more research is conducted on streams and lakes, it is likely that additional novel centric diatoms will be discovered.
Trypanosoma cruzi trans-sialidase as a multifunctional enzyme in Chagas’ disease
(Wiley, 2012) Sergio Rubin; Sérgio Schenkman
Trypanosoma cruzi trans-sialidase (TS) was identified three decades ago. TS catalyses a trans-glycosylation reaction, transferring SA from sialylated donors to the terminal galactose mucin-glycoconjugates, or non-mucin galactyosyl-glycoconjugates. It is an external surface protein that is also released from the parasite, displaying several binding properties in addition to its enzymatic function. TS structure has been solved and its catalytic properties are well known, providing tools for development of new inhibitors, as potential chemotherapeutic agents against Chagas' disease. However, there are still several unsolved questions regarding TS role in the biology of T. cruzi and in the pathology of Chagas' disease. In this review, we will describe the multifunctional roles of TS regarding the development of Chagas' disease and propose that these multiple functions have to be considered in future investigations aiming to use TS as a drug target.
Prokaryotic diversity and community composition in the Salar de Uyuni, a large scale, chaotropic salt flat
(Wiley, 2017) Sergio Rubin; Irma Marı́n; Manuel J. Gómez; Eduardo A. Morales; Ivar Zekker; Patxi San Martín‐Úriz; Núria Rodríguez; Ricardo Amils
Salar de Uyuni (SdU), with a geological history that reflects 50 000 years of climate change, is the largest hypersaline salt flat on Earth and is estimated to be the biggest lithium reservoir in the world. Its salinity reaches saturation levels for NaCl, a kosmotropic salt, and high concentrations of MgCL2 and LiCl, both salts considered important chaotrophic stressors. In addition, extreme temperatures, anoxic conditions, high UV irradiance, high albedo and extremely low concentrations of phosphorous, make SdU a unique natural extreme environment in which to contrast hypotheses about limiting factors of life diversification. Geophysical studies of brines from different sampling stations show that water activity is rather constant along SdU. Geochemical measurements show significant differences in magnesium concentration, ranging from 0.2 to 2M. This work analyses the prokaryotic diversity and community structure at four SdU sampling stations, selected according to their location and ionic composition. Prokaryotic communities were composed of both Archaea (with members of the classes Halobacteria, Thermoplasmata and Nanohaloarchaea, from the Euryarchaeota and Nanohaloarcheota phyla respectively) and Bacteria (mainly belonging to Bacteroidetes and Proteobacteria phyla). The important differences in composition of microbial communities inversely correlate with Mg2+ concentration, suggesting that prokaryotic diversity at SdU is chaotropic dependent.