Browsing by Author "Soto-Liebe, Katia"

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    COVID-19 y ciudad: hacia un modelo integrado de vivienda, microbiología, ambiente y urbanismo
    (Universitat Politecnica de Catalunya, 2021) Encinas Pino, Felipe; Soto-Liebe, Katia; Aguirre Núñez, Carlos Andrés; González, Bernardo; Bustamante, Waldo; Schueftan, Alejandra; Ugalde, Juan; Blondel, Carlos; Truffello, Ricardo; Araya, Paz; Freed, Carmen; CEDEUS (Chile)
    © 2021, Universitat Politecnica de Catalunya. All rights reserved.As of May 2020, the global health crisis caused by the SARS-CoV-2 virus moves its epicentre to Latin America, with cities showing high rates of poverty, segregation, and overcrowding. Current advances in microbiology make it possible to understand in depth the relationships between cities, COVID-19, and other microorganisms, but a conceptual framework to articulate them is lacking, especially in contexts where social determinants are so relevant. This article proposes an integrated approach to microbiology, housing, environment, and urbanism, based on a model of interactions and an empirical analysis applied to Santiago de Chile. It was possible to analyse how the propagation of COVID-19 in the city is enhanced by vulnerabilities of socio-spatial, residential and urban health, including an approach from the concept of energy poverty. At the same time, it was possible to verify how the variables associated with these vulnerabilities allowed to explain the incidence rate per 100 000 inhabitants through the different communes of Santiago de Chile. Among these, the level of housing overcrowding, the number of households with heads of household in precarious employment, and travel to the central business district stand out. Finally, the need for microbiological sampling to improve housing conditions, neighbourhoods, and cities propose a new research agenda for this Urban Microbiome" multidisciplinary team, contributing to overcoming the vulnerabilities identified in this research.
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    In Silico Analysis of Putative Paralytic Shellfish Poisoning Toxins Export Proteins in Cyanobacteria
    (2013) Soto-Liebe, Katia; Lopez-Cortes, Xaviera A.; Jose Fuentes-Valdes, Juan; Stucken, Karina; Gonzalez-Nilo, Fernando; Vasquez, Monica
    Paralytic shellfish poisoning toxins (PSTs) are a family of more than 30 natural alkaloids synthesized by dinoflagellates and cyanobacteria whose toxicity in animals is mediated by voltage-gated Na+ channel blocking. The export of PST analogues may be through SxtF and SxtM, two putative MATE (multidrug and toxic compound extrusion) family transporters encoded in PSTs biosynthetic gene cluster (sxt). sxtM is present in every sxt cluster analyzed; however, sxtF is only present in the Cylindrospermopsis-Raphidiopsis clade. These transporters are energetically coupled with an electrochemical gradient of proton (H+) or sodium (Na+) ions across membranes. Because the functional role of PSTs remains unknown and methods for genetic manipulation in PST-producing organisms have not yet been developed, protein structure analyses will allow us to understand their function. By analyzing the sxt cluster of eight PST-producing cyanobacteria, we found no correlation between the presence of sxtF or sxtM and a specific PSTs profile. Phylogenetic analyses of SxtF/M showed a high conservation of SxtF in the Cylindrospermopsis-Raphidiopsis clade, suggesting conserved substrate affinity. Two domains involved in Na+ and drug recognition from NorM proteins (MATE family) of Vibrio parahaemolyticus and V. cholerae are present in SxtF/M. The Na+ recognition domain was conserved in both SxtF/M, indicating that Na+ can maintain the role as a cation anti-transporter. Consensus motifs for toxin binding differed between SxtF and SxtM implying differential substrate binding. Through protein modeling and docking analysis, we found that there is no marked affinity between the recognition domain and a specific PST analogue. This agrees with our previous results of PST export in R. brookii D9, where we observed that the response to Na+ incubation was similar to different analogues. These results reassert the hypothesis regarding the involvement of Na+ in toxin export, as well as the motifs L(398)XGLQD(403) (SxtM) and L(390)VGLRD(395) (SxtF) in toxin recognition.
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    Impact of Nitrogen Sources on Gene Expression and Toxin Production in the Diazotroph Cylindrospermopsis raciborskii CS-505 and Non-Diazotroph Raphidiopsis brookii D9
    (2014) Stucken, Karina; John, Uwe; Cembella, Allan; Soto-Liebe, Katia; Vasquez, Monica
    Different environmental nitrogen sources play selective roles in the development of cyanobacterial blooms and noxious effects are often exacerbated when toxic cyanobacteria are dominant. Cylindrospermopsis raciborskii CS-505 (heterocystous, nitrogen fixing) and Raphidiopsis brookii D9 (non-N2 fixing) produce the nitrogenous toxins cylindrospermopsin (CYN) and paralytic shellfish toxins (PSTs), respectively. These toxin groups are biosynthesized constitutively by two independent putative gene clusters, whose flanking genes are target for nitrogen (N) regulation. It is not yet known how or if toxin biosynthetic genes are regulated, particularly by N-source dependency. Here we show that binding boxes for NtcA, the master regulator of N metabolism, are located within both gene clusters as potential regulators of toxin biosynthesis. Quantification of intra-and extracellular toxin content in cultures at early stages of growth under nitrate, ammonium, urea and N-free media showed that N-sources influence neither CYN nor PST production. However, CYN and PST profiles were altered under N-free medium resulting in a decrease in the predicted precursor toxins (doCYN and STX, respectively). Reduced STX amounts were also observed under growth in ammonium. Quantification of toxin biosynthesis and transport gene transcripts revealed a constitutive transcription under all tested N-sources. Our data support the hypothesis that PSTs and CYN are constitutive metabolites whose biosynthesis is correlated to cyanobacterial growth rather than directly to specific environmental conditions. Overall, the constant biosynthesis of toxins and expression of the putative toxin-biosynthesis genes supports the usage of qPCR probes in water quality monitoring of toxic cyanobacteria.
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    PSP toxin release from the cyanobacterium Raphidiopsis brookii D9 (Nostocales) can be induced by sodium and potassium ions
    (2012) Soto-Liebe, Katia; Mendez, Marco A.; Fuenzalida, Loreto; Krock, Bernd; Cembella, Allan; Vasquez, Monica
    Paralytic shellfish poisoning (PSP)toxins are a group of naturally occurring neurotoxic alkaloids produced among several genera of primarily freshwater cyanobacteria and marine dinoflagellates. Although saxitoxin (STX) and analogs are all potent Na+ channel blockers in vertebrate cells, the functional role of these compounds for the toxigenic microorganisms is unknown. Based upon the known importance of monovalent cations (such as sodium) in the maintenance of cellular homeostasis and ion channel function, we examined the effect of high extracellular concentrations of these ions on growth, cellular integrity, toxin production and release to the external medium in the filamentous fresh-water cyanobacterium, Raphidiopsis brookii D9; a gonyautoxins (GTX2/3) and SIX producing toxigenic strain. We observed a toxin export in response to high (17 mM) NaCl and KCl concentrations in the growth medium that was not primarily related to osmotic stress effects, compared to the osmolyte mannitol. Addition of exogenous PSP toxins with the same compositional profile as the one produced by R. brookii D9 was able to partially mitigate this effect of high Na+ (17 mM). The PSP toxin biosynthetic gene cluster (sxt) in D9 has two genes (sxtF and sxtM) that encode for a MATE (multidrug and toxic compound extrusion) transporter. This protein family, represented by NorM in the bacterium Vibrio parahaemolyticus, confers resistance to multiple cationic toxic agents through Na+/drug antiporters. Conserved domains for Na+ and drug recognition have been described in NorM. For the D9 sxt cluster, the Na+ recognition domain is conserved in both SxtF and SxtM, but the drug recognition domain differs between them. These results suggest that PSP toxins are exported directly in response to the presence of monovalent cations (Na+, K+) at least at elevated concentrations. Thus, the presence of both genes in the sxt cluster from strain D9 can be explained as a selective recognition mechanism by the SxtF/M transporters for GTX2/3 and SIX. We propose that these toxins in cyanobacteria could act extracellularly as a protective mechanism to ensure homeostasis against extreme salt variation in the environment. (C) 2012 Elsevier Ltd. All rights reserved.