Looking for the mechanism of arsenate respiration of Fusibacter sp. strain 3D3, independent of ArrAB

The literature has reported the isolation of arsenate-dependent growing microorganisms which lack a canonical homolog for respiratory arsenate reductase, ArrAB. We recently isolated an arsenate-dependent growing bacterium from volcanic arsenic-bearing environments in Northern Chile, Fusibacter sp. strain 3D3 (Fas) and studied the arsenic metabolism in this Gram-positive isolate. Features of Fas deduced from genome analysis and comparative analysis with other arsenate-reducing microorganisms revealed the lack of ArrAB coding genes and the occurrence of two arsC genes encoding for putative cytoplasmic arsenate reductases named ArsC-1 and ArsC-2. Interestingly, ArsC-1 and ArsC-2 belong to the thioredoxin-coupled family (because of the redox-active disulfide protein used as reductant), but they conferred differential arsenate resistance to the E. coli WC3110 ΔarsC strain. PCR experiments confirmed the absence of arrAB genes and results obtained using uncouplers revealed that Fas growth is linked to the proton gradient. In addition, Fas harbors ferredoxin-NAD+ oxidoreductase (Rnf) and electron transfer flavoprotein (etf) coding genes. These are key molecular markers of a recently discovered flavin-based electron bifurcation mechanism involved in energy conservation, mainly in anaerobic metabolisms regulated by the cellular redox state and mostly associated with cytoplasmic enzyme complexes. At least three electron-bifurcating flavoenzyme complexes were evidenced in Fas, some of them shared in conserved genomic regions by other members of the Fusibacter genus. These physiological and genomic findings permit us to hypothesize the existence of an uncharacterized arsenate-dependent growth metabolism regulated by the cellular redox state in the Fusibacter genus.Fil: Acosta Grinok, Mauricio. Universidad Católica del Norte; ChileFil: Vázquez, Susana Claudia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Nanobiotecnología. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Nanobiotecnología; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Microbiología, Inmunología y Biotecnología. Cátedra de Microbiología Industrial y Biotecnología; ArgentinaFil: Guiliani, Nicolás. Universidad de Chile; ChileFil: Marín, Sabrina. Universidad Católica del Norte; ChileFil: Demergasso, Cecilia. Universidad Católica del Norte; Chil

Arsenic Nanoparticles Trigger Apoptosis via Anoikis Induction in OECM-1 Cells

Arsenic compounds have been used as therapeutic alternatives for several diseases including cancer. In the following work, we obtained arsenic nanoparticles (AsNPs) produced by an anaerobic bacterium from the Salar de Ascotán, in northern Chile, and evaluated their effects on the human oral squamous carcinoma cell line OECM-1. Resazurin reduction assays were carried out on these cells using 1–100 µM of AsNPs, finding a concentration-dependent reduction in cell viability that was not observed for the non-tumoral gastric mucosa-derived cell line GES-1. To establish if these effects were associated with apoptosis induction, markers like Bcl2, Bax, and cleaved caspase 3 were analyzed via Western blot, executor caspases 3/7 via luminometry, and DNA fragmentation was analyzed by TUNEL assay, using 100 µM cisplatin as a positive control. OECM-1 cells treated with AsNPs showed an induction of both extrinsic and intrinsic apoptotic pathways, which can be explained by a significant decrease in P-Akt/Akt and P-ERK/ERK relative protein ratios, and an increase in both PTEN and p53 mRNA levels and Bit-1 relative protein levels. These results suggest a prospective mechanism of action for AsNPs that involves a potential interaction with extracellular matrix (ECM) components that reduces cell attachment and subsequently triggers anoikis, an anchorage-dependent type of apoptosis

Investigating microbial diversity and UV radiation impact at the high-altitude lake Aguas Calientes, Chile

The High-Lakes Project is funded by the NAI and explores the highest perennial volcanic lakes on Earth in the Bolivian and Chilean Andes, including several lakes ∼6,000 m elevation. These lakes represent an opportunity to study the evolution of microbial organisms in relatively shallow waters not providing substantial protection against UV radiation. Aguas Calientes (5,870 m) was investigated (November 2006) and samples of water and sediment collected at 1, 3, 5, and 10 cm depth. An Eldonet UV dosimeter positioned on the shore records UV radiation and temperature, and is logging data year round. A UV SolarLight sensor allowed acquisition of point measurements in all channels at the time of the sampling. UVA, UVB, and PAR peaks between 11:00 am and 1:00 pm reached 7.7 mW/cm2, 48.5 μW/cm2, and 511 W/m 2, respectively. The chemical composition of the water sample was analyzed. DNA was extracted and DGGE analyses with bacterial and archaeal 16S fragments were performed to describe microbial diversity. Antibiotic resistances were established previously in similar environments in Argentine Andean wetlands. In order to determine these resistances in our samples, they were inoculated onto LB and R2A media and onto R2A medium containing either chloramphenicol, ampicillin or tetracycline. Bacterial was higher than archeal cell number determined by RT-PCR in all the samples, reaching maximum total values of 5×105 cell mL-1. DGGE results from these samples and Licancabur summit lake (5,916 m) samples were also compared. Eight antibiotic-resistant Gram negative strains have been isolated with distinct resistance patterns.Fil: Escudero, Lorena. Centro de Investigación Científica y Tecnológica para la Minería; ArgentinaFil: Chong, Guillermo. Centro de Investigación Científica y Tecnológica para la Minería; ArgentinaFil: Demergasso, Cecilia. Universidad Católica de Chile; ChileFil: Farias, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Cabrol, Nathalie A.. Nasa Ames Research Center; Estados UnidosFil: Grin, Edmond. Nasa Ames Research Center; Estados UnidosFil: Minkley Jr., Edwin. University of Carnegie Mellon; Estados UnidosFil: Yu, Youngeob. University of Carnegie Mellon; Estados Unido

On the Origin of saline compounds in acidic salt flats (Central Andean Altiplano)

Volcanism, aridity, and endorheism converge in the central zone of the Andean Cordillera (Bolivia, Chile, and Argentina, between latitudes 19◦ S and 27◦ S). The Gorbea and Ignorado basins are pristine Andean sites in which the transfer of saline compounds from endogenous to exogenous environments occurs. In this area the regional volcanic rocks display strong argillic alteration, with Al and Fe (alunite, jarosite) and Ca (gypsum/ anhydrite) sulfates. Native sulfur is also present in paleosolfataras. The Gorbea salt flat is covered by a discontinuous layer of selenitic gypsum of varying thickness (maximum 2 m). The discontinuity of the layer as well as its variable thickness is due to the fact that the original bed has been partially destroyed mainly by dissolution but also by deflation. Saline pond brines (Cl-SO4-Na [-Mg]) are strongly acidic reaching pH values lower than 2. The high temperature processes that caused the hydrothermal alteration in the Gorbea and Ignorado basins occurred in the Miocene (14 Ma) coinciding with a wet period that reached 9 Ma. Subsequently, the weather up to 120 ka was predominantly hyper-arid with a less arid interval between 6 and 3 Ma and the epithermal sulfates were recycled in saline lakes mainly in the Late Pleistocene wet period (120 to 11.7 ka). Evolution into the current salt flat occurred in the mid-early Holocene (11.7 to 4 ka), through a salt lake that first evolved into a 'salina' environment that gave rise to a selenitic gypsum layer (6.4 ka), and later to the final dryness. The highest values of δ34SVCDT and δ18OVSMOW found in the selenitic gypsum layer (+20¿ and + 28¿, respectively) show that the recycling was locally produced, mainly from isotopically heavier hypogene sulfates. The δ18OVSMOW (and less clearly, δ34SVCDT) values are higher in the basal part of the gypsum crust (about +27¿), which suggests an initial hypogene source that decreased towards the top due to mixing with supergene sulfate inputs. Bacterial activity, although catalyzing the supergene reactions, does not appear to have had a significant influence on the isotopic composition of sulfates. The crystallization water of the gypsum is isotopically lighter in the basal part of the selenitic layer (δ18OVSMOW ≈ +7¿), which indicates that the brines of the saline lake were still poorly evolved. These brines evolved to heavier (approximately +13¿) towards the top of the layer and towards the center of the salt flat, before the final drying. The partial destruction of the selenitic gypsum layer occurred during more recent wet periods over the last 4 ka that have been identified in wetlands and lakes in the Central Andean area. Isotopic data (δ34SVCDT and δ18OVSMOW) clearly suggest that sulfates in the saline compounds and evaporites from the entire Central Andean arid area have mostly a thermal origin with contributions from atmospheric deposition and locally, near the Pacific coast, marine aerosols. In addition, the great difference in altitude (approximately 3000 m) between the Altiplano and the lands located to the west, up to the Pacific coast, generated a constant flow of groundwater containing saline compounds that gave rise, to the salt flats of the basins located in lower topographic areas (Atacama, Punta Negra, Hilaricos, Soledad, Tamarugal, Salar de Pintados, Salar Grande) throughout the Cenozoic. Such salt flats have lower δ34SVCDT and δ18OVSMOW valuesmostly for two reasons: the secular mixing with atmospheric sulfate, and the isotope fractionation related to repetitive dissolution (or leaking)¿migration¿precipitation along the hydraulic gradient, a process that occurred throughout a large part of the Cenozoic. The last process also explains that the evaporites of some of these salt flats (e.g., Salar de Atacama, Salar Grande) display very high Cl/SO4 ratios

Diversity of Bacteroidetes in high altitude saline evaporitic basins in northern Chile

The phylum Bacteroidetes represents one of the most abundant bacterial groups of marine and freshwater bacterioplankton. We investigated the diversity of Bacteroidetes in water and sediment samples from three evaporitic basins located in the highlands of northern Chile. We used both 16S rRNA gene clone libraries created with targeted Bacteroidetes-specific primers and separation of specifically amplified gene fragments by denaturing gradient gel electrophoresis (DGGE). DGGE analysis revealed a reduced richness of these organisms in samples from Salar de Huasco (two to four DGGE bands) increasing in Salar de Ascotán (two to seven DGGE bands) and Laguna Tebenquiche at Salar de Atacama (four to eight DGGE bands). Cluster analysis (WPGMA) of DGGE bands showed that bands from Salar de Huasco and Salar de Ascotán grouped together and samples from Salar de Atacama formed separate clusters in water and sediment samples, reflecting different Bacteroidetes communities between sites. Most of the sequences analyzed belonged to the family Flavobacteriaceae and clustered with the genera Psychroflexus, Gillisia, Maribacter, Muricauda, Flavobacterium, and Salegentibacter. The most abundant phylotype was highly related to Psychroflexus spp. and was recovered from all three study sites. The similarity of the analyzed sequences with their closest relatives in GenBank was typically <97% and notably lower when compared with type strains, demonstrating the unique character of these sequences. Culture efforts will be necessary to get a better description of the diversity of this group in saline evaporitic basins of northern Chile

Draft genome sequence of chloride-tolerant Leptospirillum ferriphilum Sp-Cl from industrial bioleaching operations in northern Chile

Indexación: Web of Science; PubMedLeptospirillum ferriphilum Sp-Cl is a Gram negative, thermotolerant, curved, rod- shaped bacterium, isolated from an industrial bioleaching operation in northern Chile, where chalcocite is the major copper mineral and copper hydroxychloride atacamite is present in variable proportions in the ore. This strain has unique features as compared to the other members of the species, namely resistance to elevated concentrations of chloride, sulfate and metals. Basic microbiological features and genomic properties of this biotechnologically relevant strain are described in this work. The 2,475,669 bp draft genome is arranged into 74 scaffolds of 74 contigs. A total of 48 RNA genes and 2,834 protein coding genes were predicted from its annotation; 55 % of these were assigned a putative function. Release of the genome sequence of this strain will provide further understanding of the mechanisms used by acidophilic bacteria to endure high osmotic stress and high chloride levels and of the role of chloride-tolerant iron-oxidizers in industrial bioleaching operations.https://standardsingenomics.biomedcentral.com/articles/10.1186/s40793-016-0142-

Hyperarid soil microbial community response to simulated rainfall

The exceptionally long and protracted aridity in the Atacama Desert (AD), Chile, provides an extreme, terrestrial ecosystem that is ideal for studying microbial community dynamics under hyperarid conditions. Our aim was to characterize the temporal response of hyperarid soil AD microbial communities to ex situ simulated rainfall (5% g water/g dry soil for 4 weeks) without nutrient amendment. We conducted replicated microcosm experiments with surface soils from two previously well-characterized AD hyperarid locations near Yungay at 1242 and 1609 masl (YUN1242 and YUN1609) with distinct microbial community compositions and average soil relative humidity levels of 21 and 17%, respectively. The bacterial and archaeal response to soil wetting was evaluated by 16S rRNA gene qPCR, and amplicon sequencing. Initial YUN1242 bacterial and archaeal 16S rRNA gene copy numbers were significantly higher than for YUN1609. Over the next 4 weeks, qPCR results showed significant increases in viable bacterial abundance, whereas archaeal abundance decreased. Both communities were dominated by 10 prokaryotic phyla (Actinobacteriota, Proteobacteria, Chloroflexota, Gemmatimonadota, Firmicutes, Bacteroidota, Planctomycetota, Nitrospirota, Cyanobacteriota, and Crenarchaeota) but there were significant site differences in the relative abundances of Gemmatimonadota and Chloroflexota, and specific actinobacterial orders. The response to simulated rainfall was distinct for the two communities. The actinobacterial taxa in the YUN1242 community showed rapid changes while the same taxa in the YUN1609 community remained relatively stable until day 30. Analysis of inferred function of the YUN1242 microbiome response implied an increase in the relative abundance of known spore-forming taxa with the capacity for mixotrophy at the expense of more oligotrophic taxa, whereas the YUN1609 community retained a stable profile of oligotrophic, facultative chemolithoautotrophic and mixotrophic taxa. These results indicate that bacterial communities in extreme hyperarid soils have the capacity for growth in response to simulated rainfall; however, historic variations in long-term hyperaridity exposure produce communities with distinct putative metabolic capacities

Surface Morphologies in a Mars-Analog Ca-Sulfate Salar, High Andes, Northern Chile

Salar de Pajonales, a Ca-sulfate salt flat in the Chilean High Andes, showcases the type of polyextreme environment recognized as one of the best terrestrial analogs for early Mars because of its aridity, high solar irradiance, salinity, and oxidation. The surface of the salar represents a natural climate-transition experiment where contemporary lagoons transition into infrequently inundated areas, salt crusts, and lastly dry exposed paleoterraces. These surface features represent different evolutionary stages in the transition from previously wetter climatic conditions to much drier conditions today. These same stages closely mirror the climate transition on Mars from a wetter early Noachian to the Noachian/Hesperian. Salar de Pajonales thus provides a unique window into what the last near-surface oases for microbial life on Mars could have been like in hypersaline environments as the climate changed and water disappeared from the surface. Here we open that climatological window by evaluating the narrative recorded in the salar surface morphology and microenvironments and extrapolating to similar paleosettings on Mars. Our observations suggest a strong inter-dependence between small and large scale features that we interpret to be controlled by extrabasinal changes in environmental conditions, such as precipitation-evaporation-balance changes and thermal cycles, and most importantly, by internal processes, such as hydration/dehydration, efflorescence/deliquescence, and recrystallization brought about by physical and chemical processes related to changes in groundwater recharge and volcanic processes. Surface structures and textures record a history of hydrological changes that impact the mineralogy and volume of Ca-sulfate layers comprising most of the salar surface. Similar surface features on Mars, interpreted as products of freeze-thaw cycles, could, instead, be products of water-driven, volume changes in salt deposits. On Mars, surface manifestations of such salt-related processes would point to potential water sources. Because hygroscopic salts have been invoked as sources of localized, transient water sufficient to support terrestrial life, such structures might be good targets for biosignature exploration on Mars