Examinando por Autor "Valdes, Jorge"

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    Generation and analysis of an Eucalyptus globulus cDNA library constructed from seedlings subjected to low temperature conditions
    (Pontificia Universidad Católica de Valparaíso, 2008) Rasmussen-Poblete, Susana; Valdes, Jorge; Gamboa, Maria Cecilia; Valenzuela, Pablo D.T.; Krauskopf, Erwin
    Eucalyptus globulus is the most important commercial temperate hardwood in the world because of its wood properties and due to its characteristics for biofuel production. However, only a very low number of expressed sequence tags (ESTs) are publicly available for this tree species. We constructed a cDNA from E. globulus seedlings subjected to low temperature and sequenced 9,913 randomly selected clones, generating 8,737 curated ESTs. The assembly produced 1,062 contigs and 3,879 singletons forming a Eucalyptus unigene set. Based on BLASTX analysis, 89.3% of the contigs and 88.5% of the singletons had significant similarity to known genes in the non-redundant database of GenBank. The Eucalyptus unigene set generated is a valuable public resource that provides an initial model for genes and regulatory pathways involved in cell wall biosynthesis at low temperature.
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    Metagenomic analysis reveals adaptations to a cold-adapted lifestyle in a low-temperature acid mine drainage stream
    (Oxford University Press, 2015-04) Liljeqvist, Maria; Ossandon, Francisco J.; González, Carolina; Rajan, Sukithar; Stell, Adam; Valdes, Jorge; Holmes, David S.; Dopson, Mark
    An acid mine drainage (pH 2.5-2.7) stream biofilm situated 250 m below ground in the low-temperature (6-10°C)Kristineberg mine, northern Sweden, contained a microbial community equipped for growth at low temperature and acidicpH. Metagenomic sequencing of the biofilm and planktonic fractions identified the most abundant microorganism to besimilar to the psychrotolerant acidophile, Acidithiobacillus ferrivorans. In addition, metagenome contigs were most similar toother Acidithiobacillus species, an Acidobacteria-like species, and a Gallionellaceae-like species. Analyses of the metagenomesindicated functional characteristics previously characterized as related to growth at low temperature including cold-shockproteins, several pathways for the production of compatible solutes and an anti-freeze protein. In addition, genes werepredicted to encode functions related to pH homeostasis and metal resistance related to growth in the acidicmetal-containing mine water. Metagenome analyses identified microorganisms capable of nitrogen fixation and exhibitinga primarily autotrophic lifestyle driven by the oxidation of the ferrous iron and inorganic sulfur compounds contained in thesulfidic mine waters. The study identified a low diversity of abundant microorganisms adapted to a low-temperature acidicenvironment as well as identifying some of the strategies the microorganisms employ to grow in this extreme environment. © FEMS 2015.
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    Regulation of a novel Acidithiobacillus caldus gene cluster involved in metabolism of reduced inorganic sulfur compounds
    (American Society for Microbiology, 0027-11-01) Rzhepishevska, Olena I.; Valdes, Jorge; Marcinkeviciene, Liucija; Gallardo, Camelia Algora; Meskys, Rolandas; Bonnefoy, Violaine; Holmes, David S.; Dopson, Mark
    Acidithiobacillus caldus has been proposed to play a role in the oxidation of reduced inorganic sulfur compounds (RISCs) produced in industrial biomining of sulfidic minerals. Here, we describe the regulation of a new cluster containing the gene encoding tetrathionate hydrolase (tetH), a key enzyme in the RISC metabolism of this bacterium. The cluster contains five cotranscribed genes, ISac1, rsrR, rsrS, tetH, and doxD, coding for a transposase, a two-component response regulator (RsrR and RsrS), tetrathionate hydrolase, and DoxD, respectively. As shown by quantitative PCR, rsrR, tetH, and doxD are upregulated to different degrees in the presence of tetrathionate. Western blot analysis also indicates upregulation of TetH in the presence of tetrathionate, thiosulfate, and pyrite. The tetH cluster is predicted to have two promoters, both of which are functional in Escherichia coli and one of which was mapped by primer extension. A pyrrolo-quinoline quinone binding domain in TetH was predicted by bioinformatic analysis, and the presence of an o-quinone moiety was experimentally verified, suggesting a mechanism for tetrathionate oxidation.