Browsing by Author "Gutierrez, Sebastian"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    Influence of Bacillus safensis and Bacillus pumilus on the electrochemical behavior of 2024-T3 aluminum alloy
    (2022) Vejar, Nelson; Gutierrez, Sebastian; Tareelap, Napachat; Alvarado, Claudia; Solis, Roberto; Guerra, Carolina; Pineda, Fabiola; Sancy, Mamie; Paez, Maritza
    In this work, electrochemical techniques were employed to evaluate the contribution to the corrosion and corrosion inhibition of 2024-T3 aluminum alloy by two Gram-positive bacteria. In addition, polarized impedance was used to determine the microbial effect on the cathodic and anodic reactions. These microorganisms were collected from a tropical environment due to the favorable bacterial growth of this kind of climate. The alloy was exposed to the sterile medium and inoculated for up to 12 days evaluating the microbiological and electrochemical behavior. The results by linear scanning voltammetry showed that the B. safensis and B. pumilus caused a dual effect of increase and decrease currents, and through electrochemical impedance spectroscopy, showed in some cases, inductive loop, which could be associated with local corrosion and another case, an increasing impedance could be related to protection. In addition, a morphological characterization was performed by scanning electron microscopy before and after exposure, showing an increase in copper precipitation in the vicinity of the intermetallic phases by bacteria, attributed to local corrosion, but, in general, a significant effect of damages was not observed. (C) 2021 Elsevier B.V. All rights reserved.
  • No Thumbnail Available
    Item
    Integrative genome-centric metagenomics for surface water surveillance: Elucidating microbiomes, antimicrobial resistance, and their associations
    (2024) Huang, Xinyang; Toro, Magaly; Reyes-Jara, Angelica; Moreno-Switt, Andrea, I; Adell, Aiko; Oliveira, Celso J. B.; Bonelli, Raquel R.; Gutierrez, Sebastian; Alvarez, Francisca P.; Rocha, Alan Douglas de Lima; Kraychete, Gabriela B.; Chen, Zhao; Grim, Christopher; Brown, Eric; Bell, Rebecca; Meng, Jianghong
    Surface water ecosystems are intimately intertwined with anthropogenic activities and have significant public health implications as primary sources of irrigation water in agricultural production. Our extensive metagenomic analysis examined 404 surface water samples from four different geological regions in Chile and Brazil, spanning irrigation canals (n = 135), rivers (n = 121), creeks (n = 74), reservoirs (n = 66), and ponds (n = 8). Overall, 50.25 % of the surface water samples contained at least one of the pathogenic or contaminant bacterial genera (Salmonella: 29.21 %; Listeria: 6.19 %; Escherichia: 35.64 %). Furthermore, a total of 1,582 antimicrobial resistance (AMR) gene clusters encoding resistance to 25 antimicrobial classes were identified, with samples from Brazil exhibiting an elevated AMR burden. Samples from stagnant water sources were characterized by dominant Cyanobacteriota populations, resulting in significantly reduced biodiversity and more uniform community compositions. A significant association between taxonomic composition and the resistome was supported by a Procrustes analysis (p < 0.001). Notably, regional signatures were observed regarding the taxonomic and resistome profiles, as samples from the same region clustered together on both ordinates. Additionally, network analysis illuminated the intricate links between taxonomy and AMR at the contig level. Our deep sequencing efforts not only mapped the microbial landscape but also expanded the genomic catalog with newly characterized metagenome-assembled genomes (MAGs), boosting the classification of reads by 12.85%. In conclusion, this study underscores the value of metagenomic approaches in surveillance of surface waters, enhancing our understanding of microbial and AMR dynamics with far-reaching public health and ecological ramifications.
  • No Thumbnail Available
    Item
    Polychromy in the Atacama Desert during the Late Intermediate Period (1000-1450 AD): pigments characterization by XRF and VNIR hyperspectral images
    (2023) Sepulveda, Marcela; Ballester, Benjamin; Cabello, Gloria; Gutierrez, Sebastian; Walter, Philippe
    The prehistory of the Atacama Desert in northern Chile has been constructed around certain traditional classes of objects, such as ceramics and lithics, following the Old World and North American standards. As such, color has been relegated to an invisible status, despite its essential visible qualities and color's importance in the region's social, symbolic, economic, and political processes. This article focuses on color and polychromy by studying objects from different funerary sites associated with the end of the regional pre-Columbian chronological sequence (ca. 1000-1500 AD). We present descriptions of the iconography and the symmetry of the motifs of these objects, and the first physicochemical characterization of the mineral paintings obtained using X-ray fluorescence spectrometry and hyperspectral imaging. With four new radiocarbon dates, we establish their chronology, associated in two cases with isotope measurements to evaluate the origin of the leather used. The research reveals a dual and simultaneous practice: while painted motifs demonstrated a visible interregional flow of information, paintings' chemical analysis testifies to a pigment production probably associated with the local exploitation of mineral coloring matter. In contrasting visual and material productions, we explore mineral pigments' social value and role during the late Atacama pre-Columbian period. Using an interdisciplinary approach regarding the materiality of color, we subsequently evaluate the social implications of mineral polychromy in this south-central Andean region.