Research Article

A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus

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Science  03 Jun 2011:
Vol. 332, Issue 6034, pp. 1163-1166
DOI: 10.1126/science.1197258
  • Fig. 1

    Growth and electron microscopy of strain GFAJ-1. (A and B) Growth curves of GFAJ-1 grown on the defined synthetic medium amended with either 1.5 mM PO43– (solid circles), 40 mM AsO43– (solid squares), or neither PO43– nor AsO43– (open triangles). Cell growth was monitored both by an increase in (A) optical density and (B) cell numbers of the cultures. Symbols represent the mean ± SD of (A) n = 6 experimental and n = 2 controls and (B) n = 3 experimental and n = 1 control. This was a single experiment with six replicates; however, material was conserved to extend the duration of the experiment to allow material for cell-counting samples. (C and D) Scanning electron micrographs of strain GFAJ-1 under two conditions, (C) +As/–P and (D) –As/+P. (E) Transmission electron micrography of +As/–P GFAJ-1 showed internal vacuole-like structures. Scale bars are as indicated in the figure (11).

  • Fig. 2

    NanoSIMS analyses of GFAJ-1: extracted DNA and whole-cells elemental ratio maps. (A) Agarose gel loaded with DNA/RNA extracted from GFAJ-1 grown (lane 2) +As/–P and (lane 3) –As/+P as compared with (lane 1) a DNA standard. Genomic bands were excised as indicated and analyzed with NanoSIMS. Ion ratios of 75As:12C of excised gel bands are indicated below with 2σ error shown (all values multiplied by 10−6). (B to G) NanoSIMS images of whole GFAJ-1 cells grown either [(B), (D), and (F)] +As/–P or [(C), (E), and (G)] –As/+P. Shown are the ion ratios of [(B) and (C)] 75As:12C, [(D) and (E)] 31P:12C, and [(F) and (G)] secondary electron (SE). Ratios in (B) and (C) are multiplied by 10−4 and in (D) and (E) are multiplied by 10−3. The color bars indicate measured elemental ratios on a log scale as indicated. Length scale is as indicated on images; images contain equivalent pixel density (11).

  • Fig. 3

    X-ray analysis of GFAJ-1 +As/–P described similarity of As coordinated like P in DNA. (A) EXAFS comparisons of the Fourier transformed data for As in model environments and GFAJ-1 (washed and fixed, collected on whole cells). Identification of each spectrum is indicated on the figure and from top to bottom are As-S, As-Fe, and GFAJ-1 data (collected on whole cells) and fit to the GFAJ-1 data (red line). (B) XRF maps indicated the correlation between As, iron (Fe) and zinc (Zn) and not with P with some variability but consistent with the trend that these elements are often found together (fig. S3, element correlation plots). The scale bar in the Zn quadrant of the maps is as designated and applies to all parts of the figure. Given the spatial resolution of these images, the structures identified as containing high As, Fe, and Zn are aggregates of cells. Ranges as indicated in the color bar run from cold to hot, in units of μg cm−2, as follows: As, 0 to 1.6; P, 0 to 40; Fe, 0 to 32.1; and Zn, 0 to 2.8. Standards were used to calibrate signal and background (11).

  • Table 1

    Bulk intracellular elemental profile of strain GFAJ-1. Cells were grown and prepared with trace metal clean techniques (11). Numbers in parentheses indicate replicate samples analyzed. As:P ratios were calculated based on all samples analyzed (11).Units are percent dry weight.

    ConditionAsPAs:P
    +As/–P (8)0.19 ± 0.250.019 ± 0.0097.3
    –As/+P (4)0.001 ± 0.00050.54 ± 0.210.002
  • Table 2

    Intracellular radiolabeled 73AsO4 arsenate distribution. All major cellular subfractions contained radiolabel after cell-washing procedures. Small molecular weight (s.m.w.) metabolites potentially include arsenylated analogs of ATP, NADH, acetyl-CoA, and others (11). SE is shown.

    Solvent (subcellular fraction)Cellular radiolabel recovered (percent of total)
    Phenol (protein + s.m.w. metabolites)80.3 ± 1.7
    Phenol:Chloroform (proteins + lipids)5.1 ± 4.1
    Chloroform (lipids)1.5 ± 0.8
    Final aqueous fraction (DNA/RNA)11.0 ± 0.1
  • Table 3

    Results of fitting arsenic K-edge EXAFS of GFAJ-1. S02 = 1, global amplitude factor and E0 = 13.97, offset for calibration. Type, the coordination type; Number, the coordination number; R, interatomic distance; and σ2, the measure of the static disorder of the shell. See table S2 for comparison to P in P-containing biomolecules (11).

    TypeNumberRσ2
    As-O4.2 (0.6)1.73 (2)0.003 (2)
    As-C2.5 (0.5)2.35 (4)0.003 (2)
    As-C2.2 (0.5)2.92 (6)0.003 (2)

Additional Files


  • A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus
    Felisa Wolfe-Simon, Jodi Switzer Blum, Thomas R. Kulp, Gwyneth W. Gordon, Shelley E. Hoeft, Jennifer Pett-Ridge, John F. Stolz, Samuel M. Webb, Peter K. Weber, Paul C. W. Davies, Ariel D. Anbar, Ronald S. Oremland

    Supporting Online Material

    This supplement contains:
    Materials and Methods
    Figs. S1 to S3
    Tables S1 to S3
    References

    Correction (3 June 2011): Several corrections and clarifications have been made to the text and tables in this file since publication. See the PDF file for the specific changes made.

    The original version can still be accessed here.

    These files are in Adobe Acrobat PDF format.

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