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GFAJ-1 Is an Arsenate-Resistant, Phosphate-Dependent Organism

Science  27 Jul 2012:
Vol. 337, Issue 6093, pp. 467-470
DOI: 10.1126/science.1218455

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  1. Fig. 1

    Growth behavior of GFAJ-1 on minimal medium containing 10 mM glucose amended with different concentrations of phosphate and arsenate. Cell growth was followed by an increase in optical density at 600 nm (OD600, open circles), or direct cell counting (closed diamonds). (A) Phosphate-dependent growth of GFAJ-1, as determined by OD600. Shown are triplicate growth curves of GFAJ-1 in the presence of 15.4 μM phosphate, as determined by elemental analysis (brown open circles); 12 μM phosphate, mixed from 15.4 μM phosphate medium and <0.3 μM phosphate medium (dark red open circles); 9 μM phosphate, mixed from 15.4 μM phosphate medium and <0.3 μM phosphate medium (red open circles); 4 μM phosphate, as determined by elemental analysis (light red open circles); 1.7 μM phosphate, as determined by elemental analysis (orange open circles); <0.3 μM phosphate, as determined by elemental analysis (pale red-violet open circles); 40 mM arsenate, <0.3 μM phosphate, as determined by elemental analysis (gray open circle). (B) Correlation of stationary phase OD600 and phosphate concentration in the medium. Shown are the results from three independently prepared batches of growth media and precultures. Red circles indicate the absence of arsenate in the growth medium. Black circles indicate the presence of 40 mM arsenate in the growth medium. Medium batch 1 (yellow filled circles); medium batch 2 (light blue filled circles); medium batch 3 (light green filled circles). (C) Phosphate-dependent growth of GFAJ-1 in the presence and absence of arsenate, as determined by OD600 and direct cell counting. Open circles indicate OD600 measurements; diamonds indicate direct cell counts. Shown are representative growth curves of GFAJ-1 cultures in the presence of 40 mM arsenate, 10 μM phosphate (black open circles, black closed diamonds); 10 μM phosphate, no arsenate (red open circles, red closed diamonds); 40 mM arsenate, <0.3 μM phosphate (pale red-violet open circles); and < 0.3 μM phosphate, no arsenate (gray open circles). (D) Dynamics of phosphorus during growth of GFAJ-1 in the presence of arsenate and limited amounts of phosphate. Shown are OD600 measurements (black open circles) and direct cell counts (black closed diamonds) of a GFAJ-1 culture in the presence of 40 mM arsenate and 10.4 μM phosphate, as well as the distribution of elemental phosphorus in the supernatant fraction (red crosses) or the cellular fraction (boxed red crosses). Phosphorus concentrations were determined by ICP-MS.