Dataset Information

Biotransformation of arsenic by a Yellowstone thermoacidophilic eukaryotic alga.

ABSTRACT: Arsenic is the most common toxic substance in the environment, ranking first on the Superfund list of hazardous substances. It is introduced primarily from geochemical sources and is acted on biologically, creating an arsenic biogeocycle. Geothermal environments are known for their elevated arsenic content and thus provide an excellent setting in which to study microbial redox transformations of arsenic. To date, most studies of microbial communities in geothermal environments have focused on Bacteria and Archaea, with little attention to eukaryotic microorganisms. Here, we show the potential of an extremophilic eukaryotic alga of the order Cyanidiales to influence arsenic cycling at elevated temperatures. Cyanidioschyzon sp. isolate 5508 oxidized arsenite [As(III)] to arsenate [As(V)], reduced As(V) to As(III), and methylated As(III) to form trimethylarsine oxide (TMAO) and dimethylarsenate [DMAs(V)]. Two arsenic methyltransferase genes, CmarsM7 and CmarsM8, were cloned from this organism and demonstrated to confer resistance to As(III) in an arsenite hypersensitive strain of Escherichia coli. The 2 recombinant CmArsMs were purified and shown to transform As(III) into monomethylarsenite, DMAs(V), TMAO, and trimethylarsine gas, with a T(opt) of 60-70 degrees C. These studies illustrate the importance of eukaryotic microorganisms to the biogeochemical cycling of arsenic in geothermal systems, offer a molecular explanation for how these algae tolerate arsenic in their environment, and provide the characterization of algal methyltransferases.

SUBMITTER: Qin J

PROVIDER: S-EPMC2664070 | biostudies-literature | 2009 Mar

REPOSITORIES: biostudies-literature

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Biotransformation of arsenic by a Yellowstone thermoacidophilic eukaryotic alga.

Qin Jie J Lehr Corinne R CR Yuan Chungang C Le X Chris XC McDermott Timothy R TR Rosen Barry P BP

Proceedings of the National Academy of Sciences of the United States of America 20090310 13

Arsenic is the most common toxic substance in the environment, ranking first on the Superfund list of hazardous substances. It is introduced primarily from geochemical sources and is acted on biologically, creating an arsenic biogeocycle. Geothermal environments are known for their elevated arsenic content and thus provide an excellent setting in which to study microbial redox transformations of arsenic. To date, most studies of microbial communities in geothermal environments have focused on Ba ...[more]

PMID: 19276121

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Project description:Purpose: We aimed at i) obtaining insight into how a thermophile organism reacts to cold stress, and ii) evaluating the impact of HGT candidates on the acclimation process to temperature decrease. Methods: The experimental design followed a temperature shift timeline: after two weeks of cultivation at 42°C, constant illumination (90 μE) and constant shaking (160 rpm) in photoautotrophic conditions the first sampling took place (Hot_T48_1) and the cultures of G.sulphuraria were swiftly moved to 28°C ( = cold temperature). "Cold" samples were taken after 3h (Cold_T3_2), 12h (Cold_T12_3) and 48h (Cold_T48_4). After cold treatment at 28°C for 48 hours, the G. sulphuraria was then switched to 46°C for 48 hours (="Hot"). Again, samples were taken after 3h (Hot_T3_5), 12h (Hot_T12_6) and 48h (Hot_T48_7). Altogether, a 48h temperature timeshift at 28°C and successive recovery at 46°C were targeted for sampling. Results: Galdieria sulphuraria is a unicellular red alga that lives in hot, acidic, toxic metal-rich, volcanic environments, where few other organisms survive. Its genome harbours up to 5% of genes most likely acquired through horizontal gene transfer. These genes probably contributed to G. sulphuraria’s adaptation to its extreme habitats, resulting in today’s polyextremophilic traits. Here, we applied RNA-sequencing to obtain insights into the acclimation of a thermophilic organism towards temperatures below its growth optimum and to study how horizontally acquired genes contribute to cold acclimation. A decrease in growth temperature from 42 °C/46 °C to 28 °C resulted in an upregulation of ribosome biosynthesis, while excreted proteins, probably components of the cell wall, were downregulated. Photosynthesis was suppressed at cold temperatures, and transcript abundances indicated that C-metabolism switched from gluconeogenesis to glycogen degradation. Folate cycle and S-adenosylmethionine cycle (one-carbon metabolism) were transcriptionally upregulated, probably to drive the biosynthesis of betaine. All these cold-induced changes in gene expression were reversible upon temperature increase. Numerous genes acquired by horizontal gene transfer displayed pronounced temperature-dependent expression changes, corroborating the view that these genes contributed to adaptive evolution in G. sulphuraria.

Dataset Information

Biotransformation of arsenic by a Yellowstone thermoacidophilic eukaryotic alga.

Publications

Biotransformation of arsenic by a Yellowstone thermoacidophilic eukaryotic alga.

Similar Datasets

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