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Community of thermoacidophilic and arsenic resistant microorganisms isolated from a deep profile of mine heaps.

Casas-Flores S, Gómez-Rodríguez EY, García-Meza JV - AMB Express (2015)

Bottom Line: We found that 0.5 g/L of As does not affect living biomass or biooxidative activity on Cu sulfides, but it dissolves Cu, while As precipitates as arsenic acid (H3AsO4·½H2O).The results indicated arsenic resistance in the microbial community, therefore specific primers were used to amplify ars (arsenic resistance system), aio (arsenite oxidase), or arr (arsenate respiratory reduction) genes from total sample DNA.Presence of arsB genes in S. thermosulfidooxidans in the Q63-66 cultures permits H3AsO4-As(V) detoxification and strengthens the community's response to As.

View Article: PubMed Central - PubMed

Affiliation: División de Biología Molecular, IPCYT, Camino a la Presa San José 2055, Lomas 4a, 78216, San Luis Potosí, SLP, México, scasas@ipicyt.edu.mx.

ABSTRACT
Soluble arsenic (As) in acidic feed solution may inhibit the copper (Cu) bioleaching process within mine heaps. To clarify the effect of soluble arsenic on the live biomass and bioxidative activity in heaps, toxicological assays were performed using a synthetic feed solution given by a mine company. The microorganisms had previously been isolated from two heap samples at up to 66 m depth, and cultured using specific media for chemolithotrophic acidophiles (pH 1-2) and moderate thermophiles (48°C), for arsenic tolerance assay. The four media with the highest biomass were selected to assay As-resistance; one culture (Q63h) was chosen to assay biooxidative activity, using a heap sample that contained chalcopyrite and covellite. We found that 0.5 g/L of As does not affect living biomass or biooxidative activity on Cu sulfides, but it dissolves Cu, while As precipitates as arsenic acid (H3AsO4·½H2O). The arsenic tolerant community, as identified by 16S rDNA gene sequence analysis, was composed of three main metabolic groups: chemolithotrophs (Leptospirillum, Sulfobacillus); chemolithoheterotrophs and organoheterotrophs as Acidovorax temperans, Pseudomonas alcaligenes, P. mendocina and Sphingomonas spp. Leptospirillum spp. and S. thermosulfidooxidans were the dominant taxa in the Q63-66 cultures from the deepest sample of the oldest, highest-temperature heap. The results indicated arsenic resistance in the microbial community, therefore specific primers were used to amplify ars (arsenic resistance system), aio (arsenite oxidase), or arr (arsenate respiratory reduction) genes from total sample DNA. Presence of arsB genes in S. thermosulfidooxidans in the Q63-66 cultures permits H3AsO4-As(V) detoxification and strengthens the community's response to As.

No MeSH data available.


Soluble Cu (a) and As (b) after 0 (initial), 7, 14, and 21 days of (bio)oxidative assays, in inoculated (experimental) and non-inoculated (control) trials (solid and dotted lines, respectively).
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Fig4: Soluble Cu (a) and As (b) after 0 (initial), 7, 14, and 21 days of (bio)oxidative assays, in inoculated (experimental) and non-inoculated (control) trials (solid and dotted lines, respectively).

Mentions: Experimental cultures that had been inoculated with microorganisms from the chemolithoheterotrophic community Q63h, exposed to the heap sample in the presence of As for 21 days, had more Cu leached (64.2% Cu removed) from Cu sulfides than the non-inoculated controls (48.7% Cu removed) (Fig. 4a). Copper leaching is mediated by acidic dissolution of covellite. On day 21, the concentration of soluble As had decreased by 78.6% in experimental, inoculated flasks, and by 63.4% in control, non-inoculated flasks (Fig. 4b). These results show that the precipitation of As occurs independently of the biomass present. By day 21, the pH had increased slightly, from 1 up to 1.4, while the Eh decreased slightly, from 700 to 650 mV, because of the decrease in Fe(III) concentration. Under these conditions, As precipitates as arsenic acid (H3AsO4).Fig. 4


Community of thermoacidophilic and arsenic resistant microorganisms isolated from a deep profile of mine heaps.

Casas-Flores S, Gómez-Rodríguez EY, García-Meza JV - AMB Express (2015)

Soluble Cu (a) and As (b) after 0 (initial), 7, 14, and 21 days of (bio)oxidative assays, in inoculated (experimental) and non-inoculated (control) trials (solid and dotted lines, respectively).
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4539307&req=5

Fig4: Soluble Cu (a) and As (b) after 0 (initial), 7, 14, and 21 days of (bio)oxidative assays, in inoculated (experimental) and non-inoculated (control) trials (solid and dotted lines, respectively).
Mentions: Experimental cultures that had been inoculated with microorganisms from the chemolithoheterotrophic community Q63h, exposed to the heap sample in the presence of As for 21 days, had more Cu leached (64.2% Cu removed) from Cu sulfides than the non-inoculated controls (48.7% Cu removed) (Fig. 4a). Copper leaching is mediated by acidic dissolution of covellite. On day 21, the concentration of soluble As had decreased by 78.6% in experimental, inoculated flasks, and by 63.4% in control, non-inoculated flasks (Fig. 4b). These results show that the precipitation of As occurs independently of the biomass present. By day 21, the pH had increased slightly, from 1 up to 1.4, while the Eh decreased slightly, from 700 to 650 mV, because of the decrease in Fe(III) concentration. Under these conditions, As precipitates as arsenic acid (H3AsO4).Fig. 4

Bottom Line: We found that 0.5 g/L of As does not affect living biomass or biooxidative activity on Cu sulfides, but it dissolves Cu, while As precipitates as arsenic acid (H3AsO4·½H2O).The results indicated arsenic resistance in the microbial community, therefore specific primers were used to amplify ars (arsenic resistance system), aio (arsenite oxidase), or arr (arsenate respiratory reduction) genes from total sample DNA.Presence of arsB genes in S. thermosulfidooxidans in the Q63-66 cultures permits H3AsO4-As(V) detoxification and strengthens the community's response to As.

View Article: PubMed Central - PubMed

Affiliation: División de Biología Molecular, IPCYT, Camino a la Presa San José 2055, Lomas 4a, 78216, San Luis Potosí, SLP, México, scasas@ipicyt.edu.mx.

ABSTRACT
Soluble arsenic (As) in acidic feed solution may inhibit the copper (Cu) bioleaching process within mine heaps. To clarify the effect of soluble arsenic on the live biomass and bioxidative activity in heaps, toxicological assays were performed using a synthetic feed solution given by a mine company. The microorganisms had previously been isolated from two heap samples at up to 66 m depth, and cultured using specific media for chemolithotrophic acidophiles (pH 1-2) and moderate thermophiles (48°C), for arsenic tolerance assay. The four media with the highest biomass were selected to assay As-resistance; one culture (Q63h) was chosen to assay biooxidative activity, using a heap sample that contained chalcopyrite and covellite. We found that 0.5 g/L of As does not affect living biomass or biooxidative activity on Cu sulfides, but it dissolves Cu, while As precipitates as arsenic acid (H3AsO4·½H2O). The arsenic tolerant community, as identified by 16S rDNA gene sequence analysis, was composed of three main metabolic groups: chemolithotrophs (Leptospirillum, Sulfobacillus); chemolithoheterotrophs and organoheterotrophs as Acidovorax temperans, Pseudomonas alcaligenes, P. mendocina and Sphingomonas spp. Leptospirillum spp. and S. thermosulfidooxidans were the dominant taxa in the Q63-66 cultures from the deepest sample of the oldest, highest-temperature heap. The results indicated arsenic resistance in the microbial community, therefore specific primers were used to amplify ars (arsenic resistance system), aio (arsenite oxidase), or arr (arsenate respiratory reduction) genes from total sample DNA. Presence of arsB genes in S. thermosulfidooxidans in the Q63-66 cultures permits H3AsO4-As(V) detoxification and strengthens the community's response to As.

No MeSH data available.