Examinando por Autor "Remonsellez, F."
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Ítem Arsenopyrite Dissolution and Bioscorodite Precipitation by Acidithiobacillus ferrivorans ACH under Mesophilic Condition(MDPI, 2022-04) Barahona, S.; Herrera, E.; Jara, A.; Castro-Severyn, J.; Gallardo, K.; Fuentes, G.; Dorador, C.; Saavedra, C.; Remonsellez, F.Arsenopyrite is the most abundant arsenic-bearing sulfide mineral in the lithosphere, usually associated with sulfide gold ores. The recovery of this highly valuable metal is associated with the release of large quantities of soluble arsenic. One way to mitigate the effects of high concentrations of arsenic in solution is to immobilize it as scorodite precipitate, a more stable form. Hence, we addressed the scorodite formation capacity (under mesophilic conditions) of psychrotolerant Acidithiobacillus ferrivorans ACH isolated from the Chilean Altiplano. Bio-oxidation assays were performed with 1% arsenopyrite concentrate as unique energy source and produced solids were evaluated by X-ray diffraction (XRD) and QEMSCAN analysis. Interestingly, the results evidenced scorodite generation as the main sub-product after incubation for 15 days, due to the presence of the microorganism. Moreover, the QEMSCAN analysis support the XRD, detecting a 3.5% increase in scorodite generation by ACH strain and a 18.7% decrease in arsenopyrite matrix, implying an active oxidation. Finally, we presented the first record of arsenopyrite oxidation capacity and the stable scorodite production ability by a member of A. ferrivorans species under mesophilic conditions.Ítem Comparative Genomics Analysis of a New Exiguobacterium Strain from Salar de Huasco Reveals a Repertoire of Stress-Related Genes and Arsenic Resistance(FRONTIERS MEDIA, 2017-03) Castro-Severyn, J.; Remonsellez, F.; Valenzuela, S.L.; Salinas, C.; Fortt, J.; Aguilar, P.; Pardo-Esté, C.; Dorador, C.; Quatrini, R.; Molina, F.; Aguayo, D.; Castro-Nallar, E.; Saavedra, C.P.The Atacama Desert hosts diverse ecosystems including salt flats and shallow Andean lakes. Several heavy metals are found in the Atacama Desert, and microorganisms growing in this environment show varying levels of resistance/tolerance to copper, tellurium, and arsenic, among others. Herein, we report the genome sequence and comparative genomic analysis of a new Exiguobacterium strain, sp. SH31, isolated from an altiplanic shallow athalassohaline lake. Exiguobacterium sp. SH31 belongs to the phylogenetic Group II and its closest relative is Exiguobacterium sp. S17, isolated from the Argentinian Altiplano (95% average nucleotide identity). Strain SH31 encodes a wide repertoire of proteins required for cadmium, copper, mercury, tellurium, chromium, and arsenic resistance. Of the 34 Exiguobacterium genomes that were inspected, only isolates SH31 and S17 encode the arsenic efflux pump Acr3. Strain SH31 was able to grow in up to 10 mM arsenite and 100 mM arsenate, indicating that it is arsenic resistant. Further, expression of the ars operon and acr3 was strongly induced in response to both toxics, suggesting that the arsenic efflux pump Acr3 mediates arsenic resistance in Exiguobacterium sp. SH31.Ítem Determinants of copper resistance in Acidithiobacillus ferrivorans ACH isolated from the Chilean altiplano(MDPI AG, 2020-08) Barahona, S.; Castro-Severyn, J.; Dorador, C.; Saavedra, C.; Remonsellez, F.The use of microorganisms in mining processes is a technology widely employed around the world. Leaching bacteria are characterized by having resistance mechanisms for several metals found in their acidic environments, some of which have been partially described in the Acidithiobacillus genus (mainly on ferrooxidans species). However, the response to copper has not been studied in the psychrotolerant Acidithiobacillus ferrivorans strains. Therefore, we propose to elucidate the response mechanisms of A. ferrivorans ACH to high copper concentrations (0–800 mM), describing its genetic repertoire and transcriptional regulation. Our results show that A. ferrivorans ACH can grow in up to 400 mM of copper. Moreover, we found the presence of several copper-related makers, belonging to cop and cus systems, as well as rusticyanins and periplasmatic acop protein in the genome. Interestingly, the ACH strain is the only one in which we find three copies of copB and copZ genes. Moreover, transcriptional expression showed an up-regulation response (acop, copZ, cusA, rusA, and rusB) to high copper concentrations. Finally, our results support the important role of these genes in A. ferrivorans copper stress resistance, promoting the use of the ACH strain in industrial leaching under low temperatures, which could decrease the activation times of oxidation processes and the energy costs. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Ítem Genetic regulation of the ompX porin of Salmonella Typhimurium in response to hydrogen peroxide stress(BioMed Central Ltd, 2022-02) Briones, A.; Lorca, D.; Cofre, A.; Cabezas, C.; Krüger, G.; Pardo-Esté, C.; Baquedano, M.; Salinas, C.; Espinoza, M.; Castro-Severyn, J.; Remonsellez, F.; Hidalgo, A.; Morales, E.; Saavedra, C.Background: Salmonella Typhimurium is a Gram-negative pathogen that causes a systemic disease in mice resembling typhoid fever. During its infective cycle, S. Typhimurium is phagocytized by macrophages and proliferates inside a Salmonella-containing vacuole where Salmonella is exposed and survives oxidative stress induced by H2O2 through modulation of gene expression. After exposure of Salmonella to H2O2, the expression of the porin-encoding gene ompX increases, as previously shown by microarray analysis. Expression of ompX mRNA is regulated at a post-transcriptional level by MicA and CyaR sRNAs in aerobiosis. In addition, sequence analysis predicts a site for OxyS sRNA in ompX mRNA. Results: In this work we sought to evaluate the transcriptional and post-transcriptional regulation of ompX under H2O2 stress. We demonstrate that ompX expression is induced at the transcriptional level in S. Typhimurium under such conditions. Unexpectedly, an increase in ompX gene transcript and promoter activity after challenges with H2O2 does not translate into increased protein levels in the wild-type strain, suggesting that ompX mRNA is also regulated at a post-transcriptional level, at least under oxidative stress. In silico gene sequence analysis predicted that sRNAs CyaR, MicA, and OxyS could regulate ompX mRNA levels. Using rifampicin to inhibit mRNA expression, we show that the sRNAs (MicA, CyaR and OxyS) and the sRNA:mRNA chaperone Hfq positively modulate ompX mRNA levels under H2O2-induced stress in Salmonella during the exponential growth phase in Lennox broth. Conclusions: Our results demonstrate that ompX mRNA is regulated in response to H2O2 by the sRNAs CyaR, MicA and OxyS is Salmonella Typhimurium.Ítem Genomic Variation and Arsenic Tolerance Emerged as Niche Specific Adaptations by Different Exiguobacterium Strains Isolated From the Extreme Salar de Huasco Environment in Chilean – Altiplano(Frontiers Media S.A., 2020-07) Castro-Severyn, J.; Pardo-Esté, C.; Mendez, K.N.; Morales, N.; Marquez, S.L.; Molina, F.; Remonsellez, F.; Castro-Nallar, E.; Saavedra, C.P.Polyextremophilic bacteria can thrive in environments with multiple stressors such as the Salar de Huasco (SH). Microbial communities in SH are exposed to low atmospheric pressure, high UV radiation, wide temperature ranges, salinity gradient and the presence of toxic compounds such as arsenic (As). In this work we focus on arsenic stress as one of the main adverse factors in SH and bacteria that belong to the Exiguobacterium genus due to their plasticity and ubiquity. Therefore, our aim was to shed light on the effect of niche conditions pressure (particularly arsenic), on the adaptation and divergence (at genotypic and phenotypic levels) of Exiguobacterium strains from five different SH sites. Also, to capture greater diversity in this genus, we use as outgroup five As(III) sensitive strains isolated from Easter Island (Chile) and The Great Salt Lake (United States). For this, samples were obtained from five different SH sites under an arsenic gradient (9 to 321 mg/kg: sediment) and isolated and sequenced the genomes of 14 Exiguobacterium strains, which had different arsenic tolerance levels. Then, we used comparative genomic analysis to assess the genomic divergence of these strains and their association with phenotypic differences such as arsenic tolerance levels and the ability to resist poly-stress. Phylogenetic analysis showed that SH strains share a common ancestor. Consequently, populations were separated and structured in different SH microenvironments, giving rise to multiple coexisting lineages. Hence, this genotypic variability is also evidenced by the COG (Clusters of Orthologous Groups) composition and the size of their accessory genomes. Interestingly, these observations correlate with physiological traits such as growth patterns, gene expression, and enzyme activity related to arsenic response and/or tolerance. Therefore, Exiguobacterium strains from SH are adapted to physiologically overcome the contrasting environmental conditions, like the arsenic present in their habitat. © Copyright © 2020 Castro-Severyn, Pardo-Esté, Mendez, Morales, Marquez, Molina, Remonsellez, Castro-Nallar and Saavedra.