Biotechnological potential of microorganisms isolated from the salar del hombre muerto, Argentina.

Bacterial strains were isolated from soil and aqueous solution samples from the Salar del Hombre Muerto, Argentina. A total of 141 strains were characterized and the tolerance to sodium chloride was evaluated. We performed a screening to search for molecules of biotechnological interest: carotenoids (11%), emulsifiers (95%), and exopolysaccharides (6%), and to assess the production of enzymes, including proteolytic (39%), lipolytic (26%), hemolytic (50%), and catalase activities (99%); 25 bacterial strains were selected for further studies. Some of them produced biofilms, but only Bacillus sp. HA120b showed that ability in all the conditions assayed. Although 21 strains were able to form emulsions, the emulsifying index Kocuria sp. M9 and Bacillus sp. V3a cultures were greater than 50% and, emulsions were more stable when the bacteria grew in higher salt concentrations. Only pigmented Kocuria sp. M9 showed lipolytic activity on olive oil medium and was able to produce biofilms when cultured without and with 4 M of NaCl. Yellow pigments, lipase activity, and biosurfactant production were observed for Micrococcus sp. SX120. Summarizing, we found that the selected bacteria produced highly interesting molecules with diverse industrial applications and, many of them are functional in the presence of high salt concentrations.

Sewershed surveillance as a tool for smart management of a pandemic in threshold countries. Case study: Tracking SARS-CoV-2 during COVID-19 pandemic in a major urban metropolis in northwestern Argentina.

Wastewater-based epidemiology is an economical and effective tool for monitoring the COVID-19 pandemic. In this study we proposed sampling campaigns that addressed spatial-temporal trends within a metropolitan area. This is a local study of detection and quantification of SARS-CoV-2 in wastewater during the onset, rise, and decline of COVID-19 cases in Salta city (Argentina) over the course of a twenty-one-week period (13 Aug to 30 Dec) in 2020. Wastewater samples were gathered from 13 sewer manholes specific to each sewershed catchment, prior to convergence or mixing with other sewer lines, resulting in samples specific to individual catchments with defined areas. The 13 sewershed catchments selected comprise 118,832 connections to the network throughout the city, representing 84.7 % (534,747 individuals) of the total population. The number of COVID19-related exposure and symptoms cases in each area were registered using an application developed for smartphones by the provincial government. Geographical coordinates provided by the devices were recorded, and consequently, it was possible to geolocalise all app-cases and track them down to which of the 13 sampling catchments belonged. RNA fragments of SARS-CoV-2 were detected in every site since the beginning of the monitoring, anticipating viral circulation in the population. Over the course of the 21-week study, the concentrations of SARS-CoV-2 ranged between 1.77 × 104 and 4.35 × 107 genome copies/L. There was a correspondence with the highest viral load in wastewater and the peak number of cases reported by the app for each catchment. The associations were evaluated with correlation analysis. The viral loads of SARS-CoV-2 in wastewater were a feasible means to describe the trends of COVID-19 infections. Surveillance at sewershed scale, provided reliable and strategic information that could be used by local health stakeholders to manage the COVID-19 pandemic.

Acanthamoeba and a bacterial endocytobiont isolated from recreational freshwaters.

The quality of many freshwater environments is impacted by human activities, so that many rivers may represent a vehicle for the transmission of health-related microorganisms. This work aimed to isolate and identify genetically free-living amoeba (FLA) of the genus Acanthamoeba from a recreational river in Salta, Argentina, and isolate, if possible, an endocytobiont. Sampling took place at four points (P1-P4) throughout the river in the winter and the summer seasons. Free-living amoebae and Acanthamoeba were recovered from 20-L water concentrated through an ultrafiltration system. Isolation was performed in agar plates, confirmation of Acanthamoeba genus by PCR, and fellow identification and classification based on their sequence analyses. High concentrations of indicator bacteria were found especially in P2, which is intensively used for recreation. Out of a total of 29 FLA isolations, 9 were identified as Acanthamoeba genotype T4 subtype A, the most frequent genotype found in nature and associated with causing human disease. From an axenic culture of Acanthamoeba spp. (KY751412), a bacterial endocytobiont was isolated, and identified as Stenotrophomonas maltophilia. The endocytobiont showed resistance and intermediate resistance to a wide range of widely used antibiotics. Results were in concordance with the cosmopolitan behavior of Acanthamoeba, and showed the importance of studying this group of amoebae and related microorganisms in recreational environments.

Propuestas para el control y la mitigación de la diseminación de COVID-19: un manejo estratégico de la enfermedad

Resumen La velocidad de diseminación del COVID-19 en el mundo llevó a que los países afectados cerraran sus fronteras y tomaran medidas de distanciamiento social. Después de seis meses de que la enfermedad fuera declarada pandemia, muchos países están tomaron medidas de flexibilización del aislamiento, aunque sin una vacuna o un medicamento capaz de enfrentar la infección por el SARS-CoV-2, la situación podría revertirse en cualquier momento. El objetivo del presente trabajo fue proponer un algoritmo de decisión tendiente a optimizar las detecciones de casos asintomáticos y administrar la cuarentena de una manera estratégica, para así evitar la diseminación del virus y tender hacia una normalidad administrada. Se elaboró una propuesta tentativa de optimización y ordenamiento de pruebas de detección del SARS-CoV-2, basada en el análisis de muestras compuestas reunidas a partir de aquellas tomadas de manera individual a personas asintomáticas que integran cohortes de interés. Se definieron cohortes según su función en la sociedad o grado de vulnerabilidad. El algoritmo contempla variables como la prioridad de la cohorte, el número de integrantes de los grupos de análisis dentro de cada cohorte, el contacto intragrupal e intergrupal, la vulnerabilidad al contagio por la actividad desarrollada y el tiempo transcurrido desde que se realizó la prueba por última vez. Se ilustró la propuesta con cohortes hipotéticas definidas, con un único grupo de análisis para simplificar, y se comprobó que la aplicación de la herramienta permite establecer de una manera racional un orden de prioridad para realizar las pruebas en grupos críticos de la sociedad. Esta herramienta permitirá optimizar recursos y disminuir el impacto de la enfermedad en la salud, la sociedad y la economía de una región.

Abstract The rapid spread of COVID-19 throughout the world, has led most of the affected countries to close their borders and implement some form of lockdown. Six months after the pandemic started, many countries made decisions tending to relax the lockdown, although wit-hout a vaccine or treatment capable of confronting SARS-CoV-2 infection, the situation could be reversed at any time. In this context, the aim of this work was to propose a decision algorithm that will allow to optimize asymptomatic case detections and strategically manage quarantine to prevent the spread of the virus and drive the transition to a managed new normal. This tentative proposal was developed for optimizing and ordering the number of tests for the detection of SARS-CoV-2, analyzing composite samples (group analysis) combining with those samples individually taken from asymptomatic members of cohorts of interest. Cohorts were defined according to their critical role in society and/or their vulnerability. The algorithm includes variables such as cohort priority, number of cohort members in the analysis groups, intra-and intergroup contact, vulnerability to contagion due to the activity performed, and time elapsed since last testing. The proposed tool was illustrated with defined hypothetical cohorts, in which, for the sake of simplification, only one analysis group was considered. The application of this tool allowed to establish in a rational way a priority order to test critical groups in society. Furthermore, this tool would help to optimize resources, reducing the impact on a region's health, society, and economy.

[Proposal for the control and mitigation of COVID-19 dissemination: strategic management of the disease]. / Propuestas para el control y la mitigación de la diseminación de COVID-19: un manejo estratégico de la enfermedad.

The rapid spread of COVID-19 throughout the world, has led most of the affected countries to close their borders and implement some form of lockdown. Six months after the pandemic started, many countries made decisions tending to relax the lockdown, although without a vaccine or treatment capable of confronting SARS-CoV-2 infection, the situation could be reversed at any time. In this context, the aim of this work was to propose a decision algorithm that will allow to optimize asymptomatic case detections and strategically manage quarantine to prevent the spread of the virus and drive the transition to a managed new normal. This tentative proposal was developed for optimizing and ordering the number of tests for the detection of SARS-CoV-2, analyzing composite samples (group analysis) combining with those samples individually taken from asymptomatic members of cohorts of interest. Cohorts were defined according to their critical role in society and/or their vulnerability. The algorithm includes variables such as cohort priority, number of cohort members in the analysis groups, intra-and intergroup contact, vulnerability to contagion due to the activity performed, and time elapsed since last testing. The proposed tool was illustrated with defined hypothetical cohorts, in which, for the sake of simplification, only one analysis group was considered. The application of this tool allowed to establish in a rational way a priority order to test critical groups in society. Furthermore, this tool would help to optimize resources, reducing the impact on a region's health, society, and economy.

Genetic fingerprint and diversity evaluation of halophilic Bacillus species by RAPD-PCR.

Random amplified polymorphic DNA-PCR (RAPD-PCR) is a technique successfully used to generate characteristic fingerprints of different bacteria. Bacillus is a genus that includes heterogeneous species, thus a combination of different techniques is essential for their identification. Here we used RAPD-PCR methodology to distinguish among genetically similar strains and to evaluate the genetic diversity of Bacillus species from the Salar del Hombre Muerto, in the Northwest of Argentina. The RAPD-PCR used allowed obtaining different amplification profiles for each Bacillus species and strains. By comparing the fingerprint profiles, we could observe that some of the salt flat isolates showed similar profiles than identified strains. As expected, the bacilli group isolated revealed a wide heterogeneity. RAPD-PCR was found to be a quick and reliable technique to evaluate the diversity of Bacillus strain and was successfully applied to characterize the genetic diversity present in the Salar del Hombre Muerto.

Genomic characterization and proteomic analysis of the halotolerant Micrococcus luteus SA211 in response to the presence of lithium.

Micrococcus luteus SA211, isolated from the Salar del Hombre Muerto in Argentina, developed responses that allowed its survival and growth in presence of high concentrations of lithium chloride (LiCl). In this research, analysis of total genome sequencing and a comparative proteomic approach were performed to investigate the responses of this bacterium to the presence of Li. Through proteomic analysis, we found differentially synthesized proteins in growth media without LiCl (DM) and with 10 (D10) and 30 g/L LiCl (D30). Bi-dimensional separation of total protein extracts allowed the identification of 17 over-synthesized spots when growth occurred in D30, five in D10, and six in both media with added LiCl. The results obtained showed different metabolic pathways involved in the ability of M. luteus SA211 to interact with Li. These pathways include defense against oxidative stress, pigment and protein synthesis, energy production, and osmolytes biosynthesis and uptake. Furthermore, mono-dimensional gel electrophoresis revealed differential protein synthesis at equivalent NaCl and LiCl concentrations, suggesting that this strain would be able to develop different responses depending on the nature of the ion. Moreover, the percentage of proteins with acidic pI predicted and observed was highlighted, indicating an adaptation to saline environments. To the best of our knowledge, this is the first report showing the relationship between protein synthesis and genome sequence analysis in response to Li, showing the great biotechnological potential that native microorganisms present, especially those isolated from extreme environments.

Halotolerant bacteria isolated from extreme environments induce seed germination and growth of chia (Salvia hispanica L.) and quinoa (Chenopodium quinoa Willd.) under saline stress.

The aim of the study was to characterize halotolerant bacteria and to evaluate their plant growth promotion potential on chia and quinoa seedlings under saline stress. Isolated microorganisms were evaluated for nitrogen fixation, phosphate solubilization, and production of siderophores and indole acetic acid. Three strains and two consortia were selected: Halomonas sp. (SFS), Micrococcus luteus (SA211), Bacillus sp. (HX11), C1 (SA211 + SFS), and C2 (SA211 + HX11). In vitro assays using water agar and half-strength Murashige-Skoog plates showed that an increase in salinity led to an increased seedlings mortality and a decrease in germination (lower than 40%), in total length (varying between 16% and 87% decreases), root length (from 60% to 92% lesser length) and dry weight (from 7% to 86% lower weight). Also, the relative growth index (RGI) decreased for both crops in most treatments, except those with HX11 and C2. These treatments had the highest growth parameters and RGI values in presence of high salinity in chia (50 and 100 mmol/L NaCl) and quinoa (200 and 400 mmol/L NaCl). SA211, the highest producer of indole acetic acid, showed a detrimental effect and anomalous phenotype on plants. Our results suggest that Bacillus sp. HX11, with multiple plant growth promotion traits and tolerance to saline stress, has a great potential as a bioinoculant in saline conditions and could be used as a biofertilizer for crop production.

Virtual screening of plant-derived compounds against SARS-CoV-2 viral proteins using computational tools.

The new SARS-CoV-2, responsible for the COVID-19 pandemic, has been threatening public health worldwide for more than a year. The aim of this work was to evaluate compounds of natural origin, mainly from medicinal plants, as potential SARS-CoV-2 inhibitors through docking studies. The viral spike (S) glycoprotein and the main protease Mpro, involved in the recognition of virus by host cells and in viral replication, respectively, were the main molecular targets in this study. Molecular docking was performed using AutoDock, which allowed us to select the plant actives with the highest affinity towards the viral targets and to identify the interaction molecular sites with the SARS-CoV2 proteins. The best energy binding values for S protein were, in kcal/mol: -19.22 for glycyrrhizin, -17.84 for gitoxin, -12.05 for dicumarol, -10.75 for diosgenin, and -8.12 for delphinidin. For Mpro were, in kcal/mol: -9.36 for spirostan, -8.75 for N-(3-acetylglycyrrhetinoyl)-2-amino-propanol, -8.41 for α-amyrin, -8.35 for oleanane, -8.11 for taraxasterol, and -8.03 for glycyrrhetinic acid. In addition, the synthetic drugs umifenovir, chloroquine, and hydroxychloroquine were used as controls for S protein, while atazanavir and nelfinavir were used for Mpro. Key hydrogen bonds and hydrophobic interactions between natural compounds and the respective viral proteins were identified, allowing us to explain the great affinity obtained in those compounds with the lowest binding energies. These results suggest that these natural compounds could potentially be useful as drugs to be experimentally evaluated against COVID-19.

Correlation between initial biodegradability determined by docking studies and structure of alkylbenzene sulfonates: A new tool for intelligent design of environmentally friendly anionic surfactants.

Gray water constitutes an important fraction of total wastewater. Some of the most problematic compounds in gray water are the anionic surfactants used as an ingredient for domestic and industrial soaps and detergents. The alkylbenzene sulfonates used in commercially available formula are highly complex mixtures of linear (LAS) and branched (BAS) molecules. LAS are classified generally as biodegradable, although their widespread use generates accumulation in the environment. Docking tools, widely used in recent years in the bioremediation field, allow molecular modeling of the ligand-enzyme interaction, which is key to understanding and evaluating the possibility of biodegradation. In this work, molecular details that allow us to establish a biodegradation pattern for some alkylbenzene sulfonates were elucidated. Two hydrogen bonds, key for the anchorage of surfactants to the monooxygenase active site involved in the initial biodegradation, were found. These bonds determine the way surfactants locate in the hydrophobic pocket of the enzyme affecting the biodegradation rate in a structurally dependent manner. For C10 to C12 linear isomers, the degradation rate increased together with the length of the hydrocarbon chain. For C13 and C14 isomers, steric difficulties to accommodate the surfactant molecule in the catalytic site were observed. For branched chain isomers, little or no biodegradation was found. In addition, biodegradation was lower in mixtures than for the pure isomers. These results will allow an intelligent design of this family of anionic surfactants to attenuate their contaminating effects in waters and soils. This study constitutes, to the best of our knowledge, a novel contribution towards the design of environmentally friendly surfactants with higher probabilities of being biodegraded to complete mineralization.

Salar del Hombre Muerto, source of lithium-tolerant bacteria.

The Salar del Hombre Muerto is a flat salt with great microbial activity despite the existing extreme conditions like high altitude, lack of water, low level of oxygen, high radiation and high concentration of sodium and lithium chloride. Despite these unfavorable conditions, we found microbial diversity with the presence of fungi, algae, and bacteria. From aqueous solutions and soil samples, a total of 238 bacteria were isolated and 186 of them were able to grow in the presence of salt. About 30% of the strains showed the ability to grow in solid medium proximally to a LiCl solution close to saturation (636 g/L). These isolates were characterized taking into account the morphology, Gram stain, ability to form biofilms and to produce pigments, and mainly according to the tolerance against lithium chloride. Bacillus was predominant among the most tolerant 26 microorganisms found, followed by Micrococcus and Brevibacterium. Members of the genera Kocuria, Curtobacterium and Halomonas were also represented among the bacteria with tolerance to 30 and 60 g/L of LiCl in defined liquid medium. All the capacities found in these microorganisms make them extremely interesting for biotechnological applications.