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Distribution of microbial arsenic reduction, oxidation and extrusion genes along a wide range of environmental arsenic concentrations.

Escudero LV, Casamayor EO, Chong G, Pedrós-Alió C, Demergasso C - PLoS ONE (2013)

Bottom Line: A combination of primers from the literature and newly designed primers were used to explore the presence of the arsC gene, coding for the reduction of As (V) to As (III) in one of the most common detoxification mechanisms.The arrA gene, involved in anaerobic respiration using As (V) as electron acceptor, was found in all the systems studied.The As (III) oxidation gene aioA and the As (III) transport gene acr3 were tracked with two primer sets each and they were also found to be spread through the As concentration gradient.

View Article: PubMed Central - PubMed

Affiliation: Centro de Investigación Científico Tecnológico para la Minería-CICITEM, Universidad Católica del Norte, Antofagasta, Chile ; Centro de Biotecnología, Universidad Católica del Norte, Antofagasta, Chile.

ABSTRACT
The presence of the arsenic oxidation, reduction, and extrusion genes arsC, arrA, aioA, and acr3 was explored in a range of natural environments in northern Chile, with arsenic concentrations spanning six orders of magnitude. A combination of primers from the literature and newly designed primers were used to explore the presence of the arsC gene, coding for the reduction of As (V) to As (III) in one of the most common detoxification mechanisms. Enterobacterial related arsC genes appeared only in the environments with the lowest As concentration, while Firmicutes-like genes were present throughout the range of As concentrations. The arrA gene, involved in anaerobic respiration using As (V) as electron acceptor, was found in all the systems studied. The As (III) oxidation gene aioA and the As (III) transport gene acr3 were tracked with two primer sets each and they were also found to be spread through the As concentration gradient. Sediment samples had a higher number of arsenic related genes than water samples. Considering the results of the bacterial community composition available for these samples, the higher microbial phylogenetic diversity of microbes inhabiting the sediments may explain the increased number of genetic resources found to cope with arsenic. Overall, the environmental distribution of arsenic related genes suggests that the occurrence of different ArsC families provides different degrees of protection against arsenic as previously described in laboratory strains, and that the glutaredoxin (Grx)-linked arsenate reductases related to Enterobacteria do not confer enough arsenic resistance to live above certain levels of As concentrations.

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Related in: MedlinePlus

Maps of the sampling location.(A) Map of northern Chile showing the areas where samples were taken: 24 in Ascotán, three in El Tatio, and 2 in Atacama. (B) Modified satellite image of Salar de Ascotán showing the location of sampling spots. The contours of As level in water was constructed using the Surfer software program (v.7.0, Golden Software, USA). Point P6 had the highest concentration in the water. Concentrations in sediments were higher in all cases.
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pone-0078890-g001: Maps of the sampling location.(A) Map of northern Chile showing the areas where samples were taken: 24 in Ascotán, three in El Tatio, and 2 in Atacama. (B) Modified satellite image of Salar de Ascotán showing the location of sampling spots. The contours of As level in water was constructed using the Surfer software program (v.7.0, Golden Software, USA). Point P6 had the highest concentration in the water. Concentrations in sediments were higher in all cases.

Mentions: Table 1 shows a summary of the geographical location, altitude and other environmental parameters for the systems studied. We chose different As-rich environments located between UTM 19 K 572171 and 603405 South and between 7427145 and 7622927 West (Fig. 1 A and B). Most sites were above 3700 m of altitude. These included several samples from the main Andean salts deposits (Salar de Ascotán), from a geothermal geyser field (El Tatio) and from incoming rivers (i.e. “quebradas”) to Salar de Atacama (Quebrada de Jere and Quebrada Aguas Blancas). No specific permissions were required for sampling in Salar de Ascotán, Quebrada de Jere, Quebrada Blanca and El Tatio. For sampling in El Tatio we informed the Comunidad Indígena de Toconce and Socaire. All these systems shared the presence of As in large or small concentrations (see Table 1). Salar de Ascotán was studied in more detail because the As concentrations were the highest found in the area. Salar de Ascotán is an athalassohaline environment located at the bottom of a tectonic basin surrounded by volcanic systems in east-west direction, including some active volcanoes over 5000 m high, with the highest altitudes close to 6000 m. Climate is characterized by large daily thermal oscillations. High solar irradiance, and strong and variable winds cause intense evaporation (about 4.5 mm day−1) while precipitation is about 120 mm year−1[41]. Water inputs include surface drainage from the snow fields on volcanoes, ground waters with a strong geothermal component and spring waters commonly reaching 23°C to 25°C. The saline crusts are mainly composed of chlorides (halite) and sulfates (gypsum) with important borate ore deposits composed mostly of ulexite with significant amounts of As sulfide minerals. This system exhibits high spatial and temporal variability with water salinities ranging from freshwater to salt-saturated brines [42].


Distribution of microbial arsenic reduction, oxidation and extrusion genes along a wide range of environmental arsenic concentrations.

Escudero LV, Casamayor EO, Chong G, Pedrós-Alió C, Demergasso C - PLoS ONE (2013)

Maps of the sampling location.(A) Map of northern Chile showing the areas where samples were taken: 24 in Ascotán, three in El Tatio, and 2 in Atacama. (B) Modified satellite image of Salar de Ascotán showing the location of sampling spots. The contours of As level in water was constructed using the Surfer software program (v.7.0, Golden Software, USA). Point P6 had the highest concentration in the water. Concentrations in sediments were higher in all cases.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3815024&req=5

pone-0078890-g001: Maps of the sampling location.(A) Map of northern Chile showing the areas where samples were taken: 24 in Ascotán, three in El Tatio, and 2 in Atacama. (B) Modified satellite image of Salar de Ascotán showing the location of sampling spots. The contours of As level in water was constructed using the Surfer software program (v.7.0, Golden Software, USA). Point P6 had the highest concentration in the water. Concentrations in sediments were higher in all cases.
Mentions: Table 1 shows a summary of the geographical location, altitude and other environmental parameters for the systems studied. We chose different As-rich environments located between UTM 19 K 572171 and 603405 South and between 7427145 and 7622927 West (Fig. 1 A and B). Most sites were above 3700 m of altitude. These included several samples from the main Andean salts deposits (Salar de Ascotán), from a geothermal geyser field (El Tatio) and from incoming rivers (i.e. “quebradas”) to Salar de Atacama (Quebrada de Jere and Quebrada Aguas Blancas). No specific permissions were required for sampling in Salar de Ascotán, Quebrada de Jere, Quebrada Blanca and El Tatio. For sampling in El Tatio we informed the Comunidad Indígena de Toconce and Socaire. All these systems shared the presence of As in large or small concentrations (see Table 1). Salar de Ascotán was studied in more detail because the As concentrations were the highest found in the area. Salar de Ascotán is an athalassohaline environment located at the bottom of a tectonic basin surrounded by volcanic systems in east-west direction, including some active volcanoes over 5000 m high, with the highest altitudes close to 6000 m. Climate is characterized by large daily thermal oscillations. High solar irradiance, and strong and variable winds cause intense evaporation (about 4.5 mm day−1) while precipitation is about 120 mm year−1[41]. Water inputs include surface drainage from the snow fields on volcanoes, ground waters with a strong geothermal component and spring waters commonly reaching 23°C to 25°C. The saline crusts are mainly composed of chlorides (halite) and sulfates (gypsum) with important borate ore deposits composed mostly of ulexite with significant amounts of As sulfide minerals. This system exhibits high spatial and temporal variability with water salinities ranging from freshwater to salt-saturated brines [42].

Bottom Line: A combination of primers from the literature and newly designed primers were used to explore the presence of the arsC gene, coding for the reduction of As (V) to As (III) in one of the most common detoxification mechanisms.The arrA gene, involved in anaerobic respiration using As (V) as electron acceptor, was found in all the systems studied.The As (III) oxidation gene aioA and the As (III) transport gene acr3 were tracked with two primer sets each and they were also found to be spread through the As concentration gradient.

View Article: PubMed Central - PubMed

Affiliation: Centro de Investigación Científico Tecnológico para la Minería-CICITEM, Universidad Católica del Norte, Antofagasta, Chile ; Centro de Biotecnología, Universidad Católica del Norte, Antofagasta, Chile.

ABSTRACT
The presence of the arsenic oxidation, reduction, and extrusion genes arsC, arrA, aioA, and acr3 was explored in a range of natural environments in northern Chile, with arsenic concentrations spanning six orders of magnitude. A combination of primers from the literature and newly designed primers were used to explore the presence of the arsC gene, coding for the reduction of As (V) to As (III) in one of the most common detoxification mechanisms. Enterobacterial related arsC genes appeared only in the environments with the lowest As concentration, while Firmicutes-like genes were present throughout the range of As concentrations. The arrA gene, involved in anaerobic respiration using As (V) as electron acceptor, was found in all the systems studied. The As (III) oxidation gene aioA and the As (III) transport gene acr3 were tracked with two primer sets each and they were also found to be spread through the As concentration gradient. Sediment samples had a higher number of arsenic related genes than water samples. Considering the results of the bacterial community composition available for these samples, the higher microbial phylogenetic diversity of microbes inhabiting the sediments may explain the increased number of genetic resources found to cope with arsenic. Overall, the environmental distribution of arsenic related genes suggests that the occurrence of different ArsC families provides different degrees of protection against arsenic as previously described in laboratory strains, and that the glutaredoxin (Grx)-linked arsenate reductases related to Enterobacteria do not confer enough arsenic resistance to live above certain levels of As concentrations.

Show MeSH
Related in: MedlinePlus