Papers by Maria Eugenia Farias
Frontiers in Microbiology
As the critical ecological engineers, biological soil crusts (biocrusts) are considered to play e... more As the critical ecological engineers, biological soil crusts (biocrusts) are considered to play essential roles in improving substrate conditions during ecological rehabilitation processes. Physical disturbance, however, often leads to the degradation of biocrusts, and it remains unclear how the physical disturbance affects biocrust microorganisms and their related metabolism. In this study, the photosynthetic biomass (indicated by chlorophyll a), nutrients, enzyme activities, and bacterial communities of biocrusts were investigated in a gold mine tailing of Central China to evaluate the impact of physical disturbance on biocrusts during the rehabilitation process of gold mine tailings. The results show that physical disturbance significantly reduced the photosynthetic biomass, nutrient contents (organic carbon, ammonium nitrogen, nitrate nitrogen, and total phosphorus), and enzyme activities (β-glucosidase, sucrase, nitrogenase, neutral phosphatase, and urease) of biocrusts in the ...
Anais da Academia Brasileira de Ciências, 2022
Aquatic biota in high altitude Andean wetlands is exposed to extreme environmental conditions tha... more Aquatic biota in high altitude Andean wetlands is exposed to extreme environmental conditions that influence ecological parameters at population and community levels. We analyzed changes in occurrence, taxa richness and relative abundance of diatom and invertebrate assemblages in four saline wetlands located at the same altitude (approx. 3,330 masl), in the Salar de Antofalla (Catamarca, Argentina). Biological samples were taken seasonally during a 1-year period, together with water variables, which were used in ordination techniques to characterize the sites. Water ionic content and biological variables, such as microcrustacean abundance and diatom richness, were evaluated as possible factors affecting the assemblages' distribution. The wetlands ranged from meso-to hyperhaline habitats and showed distinctive morphological, physical and chemical characteristics. Diatoms (42 taxa) and invertebrates (15 taxa) were collected from all sites, and diatom taxa richness was negatively correlated with water conductivity. According to multivariate analysis, the distribution of both communities was significantly explained by water hardness, whereas copepod abundance also influenced the diatom flora. We conclude that, at the same altitude and, consequently, UV radiation exposure, variables related to ionic content and/or biological parameters of the aquatic habitat may act as determinants of the biota distribution in these extreme environments.
PLOS ONE, 2016
Xanthomonas citri subsp. citri (Xcc) is the bacterium responsible for citrus canker. This bacteri... more Xanthomonas citri subsp. citri (Xcc) is the bacterium responsible for citrus canker. This bacterium is exposed to reactive oxygen species (ROS) at different points during its life cycle, including those normally produced by aerobic respiration or upon exposition to ultraviolet (UV) radiation. Moreover, ROS are key components of the host immune response. Among enzymatic ROS-detoxifying mechanisms, catalases eliminate H 2 O 2 , avoiding the potential damage caused by this specie. Xcc genome includes four catalase genes. In this work, we studied the physiological role of KatG, the only bifunctional catalase of Xcc, through the construction and characterization of a modified strain (XcckatG), carrying an insertional mutation in the katG gene. First, we evaluated the involvement of KatG in the bacterial adaptive response to H 2 O 2. XcckatG cultures exhibited lower catalase activity than those of the wild-type strain, and this activity was not induced upon treatment with sub-lethal doses of H 2 O 2. Moreover, the KatG-deficient mutant exhibited decreased tolerance to H 2 O 2 toxicity compared to wild-type cells and accumulated high intracellular levels of peroxides upon exposure to sub-lethal concentrations of H 2 O 2. To further study the role of KatG in Xcc physiology, we evaluated bacterial survival upon exposure to UV-A or UV-B radiation. In both conditions, XcckatG showed a high mortality in comparison to Xcc wild-type. Finally, we studied the development of bacterial biofilms. While structured biofilms were observed for the Xcc wild-type, the development of these structures was impaired for XcckatG. Based on these results, we demonstrated that KatG is responsible for Xcc adaptive response to H 2 O 2 and a key component of the bacterial response to oxidative stress. Moreover, this enzyme plays an important role during Xcc epiphytic survival, being essential for biofilm formation and UV resistance.
Journal of Astrobiology & Outreach, 2015
The Mars Exploration Rover Spirit investigated plains at Gusev crater, where sedimentary rocks ar... more The Mars Exploration Rover Spirit investigated plains at Gusev crater, where sedimentary rocks are present. The Spirit rover's Athena morphological investigation shows microstructures organized in intertwined filaments of microspherules: a texture we have also found on samples of terrestrial stromatolites and other microbialites. We performed a quantitative image analysis to compare 45 microbialites samplings with 50 rover's ones (approximately 25,000/20,000 microstructures). Contours were extracted and morphometric indexes obtained: geometric and algorithmic complexities, entropy, tortuosity, minimum and maximum diameters. Terrestrial and Martian textures resulted multifractals, while terrestrial abiogenic minerals showed a simple fractal structure. Mean values and confidence intervals from the Martian images overlapped perfectly with those from terrestrial samples. The probability of this occurring by chance was less than 1/2 8 , p<0.004. Our work show the presumptive evidence of microbialites in the Martian outcroppings explored by "Spirit", confirming our previous results concerning the Martian outcroppings explored by Opportunity at Meridiani Planum: unicellular life was widespread on the ancient Mars.
Letters in Applied Microbiology, 2011
Aims: To identify and compare microbiota in Chinese liquor Daqu, which were produced in the diffe... more Aims: To identify and compare microbiota in Chinese liquor Daqu, which were produced in the different regions using different production process. Methods and Results: The DNA exacted from Daqu samples was used as a template for PCR with universal primers of 16S rRNA, 26S rRNA and 18S rRNA, respectively. The amplicons were analysed using denaturing gradient gel electrophoresis (DGGE). It was observed that the bacterial DGGE profile indicated high diversity and predominance of lactic acid bacteria. The results showed that Saccharomycopsis fibuligera and Pichia anomal were dominant yeast species and that several non-Saccharomyces yeasts including Hanseniaspora guilliermondii, Debaryomyces hansenii, Issatchenkia orientalis and Trichosporon asahii were also detected. As for fungal DGGE, Aspergillus oryzae and Absidia blakesleeana were the most common species amongst different samples. Based on the DGGE analysis, a few differences in community structure were found between Daqu samples. Conclusions: A variety of bacteria, yeast and moulds were identified in Daqu samples, in addition to the present knowledge obtained mainly through the traditional culture-dependent methods. Moreover, production temperature played a more decisive role on the formation of microorganism composition in Daqu than geographical region. Significance and Impact of the Study: PCR-DGGE technique was used in this study to fully observe and asses all microbial community (including bacteria, yeast and mould) in Chinese liquor Daqu for the first time and proved to be effective in profiling Daqu microbial diversity.
International Journal of Systematic and Evolutionary Microbiology, 2010
A Gram-stain-negative, aerobic, rod-shaped, non-spore-forming bacterium (SV325T) was isolated fro... more A Gram-stain-negative, aerobic, rod-shaped, non-spore-forming bacterium (SV325T) was isolated from the sediment of a hypersaline lake located 4600 m above sea level (Laguna Vilama, Argentina). Strain SV325T formed cream to pink colonies, was motile and moderately halophilic, and tolerated NaCl concentrations of 1–25 % (w/v) with an optimum of 5–10 % (w/v). Growth occurred at 5–40 °C (optimum around 30 °C) and at pH 5.0–10.0 (optimum 7.0–8.0). The bacterium did not produce exopolysaccharides and stained positively for intracellular polyphosphate granules but not for poly-β-hydroxyalkanoates. It produced catalase and oxidase, reduced nitrate to nitrite, hydrolysed gelatin, did not produce acids from sugars and utilized a limited range of substrates as carbon and energy sources: acetate, caproate, fumarate, dl-β-hydroxybutyrate, malate, maleate, malonate and succinate. The predominant ubiquinones were Q-9 (92.5 %) and Q-8 (7.5 %), the major fatty acids were C19 : 0 cyclo ω8c, C16 : 0, ...
Recent Patents on Anti-infective Drug Discovery, 2009
High altitude Andean lakes are placed in Puna desert over 4400 above sea level. Completely isolat... more High altitude Andean lakes are placed in Puna desert over 4400 above sea level. Completely isolated, they are exposed to extreme environmental factors like high levels of salinity, UV radiation and heavy metals and low concentrations of phosphorus. Nevertheless, they are the habitat of enormous populations of three flamingo species that migrate among these Lakes. Previous reports have determined that bacteria isolated from these environments present high levels of resistance to antibiotics. The aim of this work was to determine the diversity of antibiotic resistant bacteria in water from Andean Lakes and their connection with flamingo enteric biota. Bacteria from water and birds faeces from high altitude Lakes: Laguna (L.) Aparejos, L. Negra, L. Vilama and L. Azul (all are located between 4,200 and 4,600 m altitude) were isolated by plating in five different Antibiotics (ampicillin, 100 g ml-1 ; chloramphenicol, 170 g ml-1 ; colistin , 20 g ml-1 ; erythromycin, 50 g ml-1 and tetracycline 50 g ml-1). 56 bacteria were isolated and identified by 16 S rDNA sequencing. Antibiotic resistance profiles of isolated bacteria were determined for 22 different antibiotics. All identified bacteria were able to growth in multiple ATBs. Colistin, ceftazidime, ampicillin/sulbactam, cefotaxime, cefepime, cefalotin, ampicillin and erythromycin were the most distributed resistances among the 56 tested bacteria The current results demonstrated that antibiotic resistance was abundant and diverse in high altitude Lakes. Also the present article indicates some useful patents regarding the isolation of bacteria able to grow in the present of antibiotics.
Springer eBooks, 2020
Based on the aridity index of 0.05, the Atacama Desert is considered a hyperarid area with extrem... more Based on the aridity index of 0.05, the Atacama Desert is considered a hyperarid area with extremely dry conditions (Wierzchos et al. 2012). Because of its aridity and UV incidence, it is largely compared to Mars, and it is also at the dry limit of microbial life (Navarro-Gonzalez et al. 2003). In addition, it is the Earth's largest modern evaporitic regions, which comprises a large number of salt flats, with a combination of evaporitic crusts and saline lakes or playa-lakes (locally referred to as "lagunas") (Stoertz and Ericksen 1974; Risacher et al. 2003). The Salar de Llamara is located in the north of the Atacama Desert (Fig. 11.1a). This is one of the aridest parts of the desert span toward northern Chile, and it is situated between the rain shadows of the Andes Mountains and the Coastal Cordillera (Michalski et al. 2004). Llamara 1 (L1) and Llamara 2 (L2) are two shallow wetlands at an approximately 500 m distance, containing two kinds of complex and diverse stratified microbial communities, microbial mats (Demergasso et al. 2003; Rasuk et al. 2016), and evaporitic domes (Rasuk et al. 2014, ongoing publication) (Fig. 11.1). The occurrence of microbial life associated with these desert environments opens up new perspectives regarding how communities adapt to and tolerate extreme environmental conditions and increases our understanding of microbial ecology and evolution. Thus, the present book chapter comprises all the available information about the stratified microbial ecosystems located in the Salar de Llamara.
Frontiers in Microbiology, Mar 15, 2022
Proteomics of Nesterenkonia UV-Resistome well-defined set of proteins while recovery treatments r... more Proteomics of Nesterenkonia UV-Resistome well-defined set of proteins while recovery treatments restored the proteomic profiles present before the UV-challenge. The proteins involved in this complex molecular network were categorized within the UV-resistome subsystems: damage tolerance and oxidative stress response, energy management and metabolic resetting, and DNA damage repair.
Microbial Ecology, Mar 8, 2018
Biofilms, microbial mats, and microbialites dwell under highly limiting conditions (high salinity... more Biofilms, microbial mats, and microbialites dwell under highly limiting conditions (high salinity, extreme aridity, pH, and elevated arsenic concentration) in the Andean Puna. Only recent pioneering studies have described the microbial diversity of different Altiplano lakes and revealed their unexpectedly diverse microbial communities. Arsenic metabolism is proposed to be an ancient mechanism to obtain energy by microorganisms. Members of Bacteria and Archaea are able to exploit arsenic as a bioenergetic substrate in either anaerobic arsenate respiration or chemolithotrophic growth on arsenite. Only six aioAB sequences coding for arsenite oxidase and three arrA sequences coding for arsenate reductase from haloarchaea were previously deposited in the NCBI database. However, no experimental data on their expression and function has been reported. Recently, our working group revealed the prevalence of haloarchaea in a red biofilm from Diamante Lake and microbial mat from Tebenquiche Lake using a metagenomics approach. Also, a surprisingly high abundance of genes used for anaerobic arsenate respiration (arr) and arsenite oxidation (aio) was detected in the Diamante's metagenome. In order to study in depth the role of arsenic in these haloarchaeal communities, in this work, we obtained 18 haloarchaea belonging to the Halorubrum genus, tolerant to arsenic. Furthermore, the identification and expression analysis of genes involved in obtaining energy from arsenic compounds (aio and arr) showed that aio and arr partial genes were detected in 11 isolates, and their expression was verified in two selected strains. Better growth of two isolates was obtained in presence of arsenic compared to control. Moreover, one of the isolates was able to oxidize As[III]. The confirmation of the oxidation of arsenic and the transcriptional expression of these genes by RT-PCR strongly support the hypothesis that the arsenic can be used in bioenergetics processes by the microorganisms flourishing in these environments.
World Journal of Microbiology & Biotechnology, Aug 31, 2021
Central-Andean Ecosystems (between 2000 and 6000 m above sea level (masl) are typical arid-to-sem... more Central-Andean Ecosystems (between 2000 and 6000 m above sea level (masl) are typical arid-to-semiarid environments suffering from the highest total solar and ultraviolet-B radiation on the planet but displaying numerous salt flats and shallow lakes. Andean microbial ecosystems isolated from these environments are of exceptional biodiversity enduring multiple severe conditions. Furthermore, the polyextremophilic nature of the microbes in such ecosystems indicates the potential for biotechnological applications. Within this context, the study undertaken used genome mining, physiological and microscopical characterization to reveal the multiresistant profile of Nesterenkonia sp. Act20, an actinobacterium isolated from the soil surrounding Lake Socompa, Salta, Argentina (3570 masl). Ultravioet-B, desiccation, and copper assays revealed the strain's exceptional resistance to all these conditions. Act20's genome presented coding sequences involving resistance to antibiotics, low temperatures, ultraviolet radiation, arsenic, nutrient-limiting conditions, osmotic stress, low atmospheric-oxygen pressure, heavy-metal stress, and toxic fluoride and chlorite. Act20 can also synthesize proteins and natural products such as an insecticide, bacterial cellulose, ectoine, bacterial hemoglobin, and even antibiotics like colicin V and aurachin C. We also found numerous enzymes for animal-and vegetal-biomass degradation and applications in other industrial processes. The resilience of Act20 and its biotechnologic potential were thoroughly demonstrated in this work.
bioRxiv (Cold Spring Harbor Laboratory), Dec 10, 2019
Phosphate and arsenate are very similar compounds, and there is great interest in studying their ... more Phosphate and arsenate are very similar compounds, and there is great interest in studying their relationship and their interaction with biological systems. Despite having no apparent biological function, specific genes regulate arsenic interaction with cells and can be located in regions of the genome called arsenic islands, where phosphate metabolism genes are also present. Although they are neighboring genes, the nature of their relationship and how they have been selected is still unknown. In this work, we analyzed the metagenomes of the four microbial ecosystems inhabiting hypersaline lakes of the Argentine Puna and the Atacama salt flat in Chile and have evaluated the presence and abundance of both arsenic and phosphate metabolism genes. The samples analyzed included microbialites, biofilms and microbial mats; all of them established under high arsenic concentrations, high UV radiation and high temperature fluctuation, among others. The results show great differences in the dispersion and abundance of genes related to both phosphate and arsenic metabolism in the analyzed samples. The main difference is given in the Diamante Lake, located in the crater of the Galan volcano characterized by being one of the lakes with the highest arsenic concentration (2.34 mM). Correlating genes abundance with the physicochemical parameters of the lakes studied, our results suggest that arsenic and phosphate metabolism are intricately co-regulated in environmental conditions. Keywords: arsenate and phosphate, Pst transport system, arsenic respiration, Andean Microbial Ecosystem. Introduction Phosphorus is typically found in nature as inorganic phosphate (Pi). Together with carbon, hydrogen, nitrogen, oxygen, and sulfur, Pi is one of the six chemical elements essential to life as we know it (Karl 2000; Rasuk et al. 2016). Pi is involved in many cellular functions as it is part of DNA and RNA, ATP and polyphosphates (polyP) (Kornberg 1999
Data pertain the study of arsenic and sulfur supported microbial metabolisms in a permanently ano... more Data pertain the study of arsenic and sulfur supported microbial metabolisms in a permanently anoxic microbial mat in the Atacama Desert, Chile.
ABSTRACTModern non-lithifying stromatolites (STs) on the shore of the volcanic lake Socompa in th... more ABSTRACTModern non-lithifying stromatolites (STs) on the shore of the volcanic lake Socompa in the Puna are affected by several extreme conditions. Although STs were proposed as ecologic models for understanding stress response and resilience in microbial ecosystems constituting a window into the past, our knowledge of ST function is still nascent. The present study assesses for the first time light utilization and functional metabolic stratification of STs on a millimeter scale through shotgun metagenomics. In addition, a scanning-electron-microscopy approach was used to explore the community. Our results demonstrated that Bacteroidetes and Cyanobacteria play major roles as ST builders and primary producers to sustain a diverse community of heterotrophs. STs manifest a high occurrence of genes for the synthesis of UV-protecting pigments, the cryptochrome-photolyase family (CPF), and rhodopsins in the surface layers. Three different ecologic niches involving the use of light in ener...
Flamingos Phoenicopteridae sp. are gregarious birds that travel long distances between breeding a... more Flamingos Phoenicopteridae sp. are gregarious birds that travel long distances between breeding and feeding sites. Here we describe the diet and feeding selectivity of two flamingo species, the Andean Flamingo Phoenicoparrus andinus and Chilean Flamingo Phoenicopterus chilensis, which coexist in a lowland area of Argentina. Environmental characteristics and available food resources were assessed at twelve lakes where feeding flocks of both species of flamingos occurred. Food items found in faeces (16S rRNA for bacteria and archaea) and microscopic analyses (for Cyanobacteria, microalgae and microinvertebrates) were analysed, and the birds’ feeding selectivity and niche overlap were estimated. Results showed that the lakes were of eutrophic to hypereutrophic status, and with hypohaline to mesohaline salinity levels. Predominant microorganisms belonged to the Planctomycetes, Verrucomicrobia, Chloroflexi, Euryarchaeota, Cyanobacteria, Bacillariophyta and Copepoda phyla. Euryarchaeota a...
Photochemistry and photobiology, May 1, 2017
Polyextremophiles are present in a wide variety of extreme environments in which they must overco... more Polyextremophiles are present in a wide variety of extreme environments in which they must overcome various hostile conditions simultaneously such as high UVB radiation, extreme pHs and temperatures, elevated salt and heavy-metal concentration, low-oxygen pressure and scarce nutrients. High-altitude Andean lakes (HAALs; between 2000 and 4000 m) are one example of these kinds of ecosystems suffering from the highest total solar and UVB radiation on Earth where an abundant and diverse polyextremophilic microbiota was reported. In this work, we performed the first extensive isolation of UV-resistant actinobacteria from soils, water, sediments and modern stromatolites at HAALs. Based on the 16S rRNA sequence, the strains were identified as members of the genera Streptomyces, Micrococcus, Nesterenkonia, Rhodococcus, Microbacterium, Kocuria, Arthrobacter, Micromonospora, Blastococcus, Citrococcus and Brevibacterium. Most isolates displayed resistance to multiple environmental stress facto...
PLOS ONE, 2016
Economic losses caused by postharvest diseases represent one of the main problems of the citrus i... more Economic losses caused by postharvest diseases represent one of the main problems of the citrus industry worldwide. The major diseases affecting citrus are the "green mold" and "blue mold", caused by Penicillium digitatum and P. italicum, respectively. To control them, synthetic fungicides are the most commonly used method. However, often the emergence of resistant strains occurs and their use is becoming more restricted because of toxic effects and environmental pollution they generate, combined with trade barriers to international markets. The aim of this work was to isolate indigenous killer yeasts with antagonistic activity against fungal postharvest diseases in lemons, and to determine their control efficiency in in vitro and in vivo assays. Among 437 yeast isolates, 8.5% show to have a killer phenotype. According to molecular identification, based on the 26S rDNA D1/D2 domain sequences analysis, strains were identified belonging to the genera Saccharomyces, Wickerhamomyces, Kazachstania, Pichia, Candida and Clavispora. Killers were challenged with pathogenic molds and strains that caused the maximum in vitro inhibition of P. digitatum were selected for in vivo assays. Two strains of Pichia and one strain of Wickerhamomyces depicted a significant protection (p <0.05) from decay by P. digitatum in assays using wounded lemons. Thus, the native killer yeasts studied in this work showed to be an effective alternative for the biocontrol of postharvest fungal infections of lemons and could be promising agents for the development of commercial products for the biological control industry.
Extremophiles, Jan 3, 2013
Lipid storage in high-altitude Andean Lakes extremophiles and its mobilization under stress condi... more Lipid storage in high-altitude Andean Lakes extremophiles and its mobilization under stress conditions in Rhodococcus sp.
BioMed Research International, Feb 21, 2019
High levels of arsenic present in the High Altitude Andean Lakes (HAALs) ecosystems selected arse... more High levels of arsenic present in the High Altitude Andean Lakes (HAALs) ecosystems selected arsenic-resistant microbial communities which are of novel interest to study adaptations mechanisms potentially useful in bioremediation processes. We herein performed a detailed characterization of the arsenic tolerance profiles and the biofilm production of two HAAL polyextremophiles, Acinetobacter sp. Ver3 (Ver3) and Exiguobacterium sp. S17 (S17). Cellular adherence over glass and polypropylene surfaces were evaluated together with the effect of increasing doses and oxidative states of arsenic over the quality and quantity of their biofilm production. The arsenic tolerance outcomes showed that HAAL strains could tolerate higher arsenic concentrations than phylogenetic related strains belonging to the German collection of microorganisms and cell cultures (Deutsche Sammlung von Mikroorganismen und Zellkulturen, DSMZ), which suggest adaptations of HAAL strains to their original environment. On the other hand, the crystal violet method (CV) and SEM analysis showed that Ver3 and S17 were able to attach to solid surfaces and to form the biofilm. The quantification of biofilms production in 48 hours' cultures through CV shows that Ver3 yielded higher production in the treatment without arsenic cultured on a glass support, while S17 yield higher biofilm production under intermediate arsenic concentration on glass supports. Polypropylene supports had negative effects on the biofilm production of Ver3 and S17. SEM analysis shows that the highest biofilm yields could be associated with a larger number of attached cells as well as the development of more complex 3D multicellular structures.
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Papers by Maria Eugenia Farias