Conclusion These observations revealed that carbon assimilation, energy acquisition and arsenic
metabolism of these strains are linked. However, they do not share a common mechanism, since metabolisms required for growth and carbon assimilation are stimulated in T. arsenivorans in the presence of arsenic, but repressed in Thiomonas sp. 3As. Further Cytoskeletal Signaling inhibitor work is needed to test if a common mechanism occurs to regulate carbon assimilation and arsenic response in other Thiomonas strains. However, to our knowledge, this is the first example of such a link between arsenic metabolism and carbon assimilation. Methods Culture media All strains except T. arsenivorans were routinely cultured on m126 (modified 126 medium) gelled or liquid medium. Medium m126 contains: (g L-1) yeast extract (YE; 0.5); Na2S2O3 (5.0); KH2PO4 (1.5); Na2HPO4 (4.5); MgSO4·7H2O (0.1); (NH4)Cl (0.3), adjusted to pH 5.0 with H2SO4 prior to sterilisation. T. arsenivorans was routinely cultured on a modified MCSM medium (MCSM)  with vitamins and trace elements omitted, yeast extract added to a final concentration of 0.5 g L-1 and Na2S2O3 to a final concentration of 2.5 g L-1. Variations of these media included omitting yeast extract and/or thiosulfate. Where no yeast extract was included, trace elements were added, as described previously . Where required, the media were gelled by the addition of 12 g L-1 agar
(final concentration). buy CP-690550 arsenite (As(III)) and arsenate (As(V)) were added to media to the desired concentration from sterile stocks of 667.4 mM of the metalloid ion in ddH2O, from NaAsO2 (Prolabo) and Na2HAsO4·7H20 CP673451 clinical trial (Prolabo) salts, respectively. Physiological tests Minimum inhibitory concentration (MIC) experiments were performed using gelled media, amended with a range of concentrations of either arsenite or arsenate. Concentrations of 10, 5.0, 2.25, 1.25 and
0 mM As(III) or 100, 50, 25, 12.5, 6.3 and 0 mM As(V) were tested at Selleckchem Staurosporine 30°C for up to 10 days. The ability of each strain to oxidise arsenite was tested in triplicate, in liquid media amended with 0.67 mM arsenite. Detection of As(III) and As(V) was performed by inductively coupled plasma-atomic emission spectrometry (ICP-AES) as described by Weeger et al. . To test the ability of each strain to grow in the absence of a reduced inorganic sulfur source or organic carbon source, pre-cultures grown in standard media were harvested by centrifugation at 10 K g for 10 min, washed and resuspended in a basal medium (m126 medium with no thiosulfate or yeast extract). These were then used to inoculate the test liquid media and incubated at 30°C for 10 days. Soluble sulfate concentrations were determined turbidimetrically by the formation of insoluble barium sulfate, as described by Kolmert et al. . Bacterial growth in media containing YE was assessed using optical density at 600 nm.