Nano3

¹⁵³Gd(III) chloride and ²³³U(VI) nitrate were purchased from Eckert & Ziegler Isotope Products (Valencia, CA). ¹⁷⁷Lu(III) chloride was purchased from Perkin Elmer Health Sciences (Shelton, CT). A Pu(IV) chloride stock solution containing a 50/50 mixture (Bq/Bq) of ²⁴¹Pu and ²⁴²Pu and a stock solution of ²⁴³Am(III), prepared by dissolution of ²⁴³Am₂O₃ in 1 M HNO₃, were from LBNL inventory. ²²⁵Ac(III), ²⁴⁹Bk(III), and ²⁴⁹Cf(III) were obtained as chlorides from ORNL. A ²⁵³Es(III) perchlorate solid sample was provided by Prof. J. Shafer (Colorado School of Mines). 343HOPO was from LBNL inventory^{14 (link)}. Standard solutions of 0.1 M and 6.0 M HNO₃ (BDH VWR Analytical), 70% HNO₃ (Sigma Aldrich), NaNO₃ (>99%, ACS grade, VWR), sodium lactate (Sigma Aldrich), TODGA (>99%, Technocomm Ltd.), HDEHP (>95%, Merck), tributyl phosphate (TBP, >98%, Alpha Aesar), kerosene low odor (Alpha Aesar), DTPA (>98%, TCI), and Ultima Gold LLT (Perkin Elmer) were used as received. All solutions were prepared using deionized water purified by a Millipore Milli-Q reverse osmosis cartridge system. Stocks were stored at 8 °C in the dark between experiments.

A. platensis PCC7345 was obtained from the Pasteur Culture Collection (PCC, Paris, France). Stock cultures were grown in a sterile filtrated modified Zarrouk medium containing (g/L): 16.8 NaHCO₃ (99.5%, VWR Chemicals, Darmstadt, Germany), 0.5 K₂HPO₄ (99%, Carl Roth, Karlsruhe, Germany), 2.5 NaNO₃ (99.9%, VWR chemicals, Darmstadt, Germany), 1.0 K₂SO₄ (99.5%, VWR chemicals, Darmstadt, Germany), 1.0 NaCl (99%, Carl Roth, Karlsruhe, Germany), 0.2 MgSO₄∙7H₂O (99%, Carl Roth, Karlsruhe, Germany), 0.04 CaCl₂∙2H₂O (99%, Carl Roth, Karlsruhe, Germany) [11 (link)], and 100 µL/L of Hutner’s trace element solution [49 ]. A. platensis stock cultures were maintained in 300 mL Erlenmeyer flasks at 26 °C, 150 rpm, and 75 µmol/m²s fluorescent light (light/dark cycles of 16/8 h, WB750, Mytron Bio- und Solartechnik GmbH, Heilbad Heiligenstadt, Germany). Liquid stock cultures were sub-cultivated every two weeks to prevent aging and cell death.

NaNO₃ was obtained from VWR international (Lutterworth, Leicestershire, UK). Sodium nitrite (NaNO₂), N-ethylmaleimide (NEM), Nonidet™ P 40 Substitute, mercuric chloride (HgCl₂) and 1 M hydrochloric acid (HCl) were obtained from Sigma-Aldrich Ltd. (Gillingham, UK). S-nitrosoglutathione (GSNO) was obtained from Enzo Life Sciences (Exeter, UK). Sodium iodide (NaI), potassium iodide (KI), iodine (I₂), acetic acid (99.5%), ethylenediaminetetraacetic acid (EDTA), vanadium (III) chloride (VCl₃), potassium ferricyanide, sulfanilamide and methanol were obtained from Fisher Scientific (Loughborough, Leicestershire, UK). Lithium-heparin tubes were obtained from Becton Dickinson UK Ltd. (Wokingham, UK). Cannulas were obtained from Becton Dickinson Insyte-WTM (Madrid, Spain). NO₃⁻-rich beetroot juice (BR; beetroot juice containing 6.4 mmol of NO₃⁻ per 70 ml; “Beet It Sport”) and NO₃⁻-depleted beetroot juice (PL; beetroot juice containing 0.04 mmol of NO₃⁻ per 70 ml) were obtained as gifts from James White Drinks Ltd. (Ipswich, UK). The reagents and buffers were made up in ultrapure water (18.2 MΩ/cm) unless otherwise indicated.

We used the S. robusta strain PONTON36 (24.0 ± 0.6 μm), which is accessible at the Belgian Coordinated Culture Collection of Microorganisms (bccm.belspo.be, accession number DCG 0462). Cultivation was performed in 40‐ml TC flasks (Sarstedt, Germany) in buffered artificial sea water (ASW) modified after Maier & Calenberg (1994) at 18°C in a 12:12 hr light:dark regime with cool‐white fluorescent lamps at approximately 35 μmol photons m⁻² s⁻¹. The nutrient concentrations in the medium were set at 621 μM NaNO₃ (VWR Chemicals, Leuven, Belgium), 15 μM K₂HPO₄ (Roth, Karlsruhe, Germany), and 246 μM Na₂SiO₃·9 H₂O (Sigma‐Aldrich, Steinheim, Germany).