Dataset: Iron use efficiency (IUE) of the model marine ammonia-oxidizing archaea (AOA), Nitrosopumilus maritimus, under controlled laboratory conditions across a range of temperatures and iron concentrations

Trace metal clean culturing experiments were conducted using the marine ammonia-oxidizing archaeon Nitrosopumilus maritimus (urn:lsid:marinespecies.org:taxname:559434) grown in 2.7 L trace metal clean polycarbonate bottles containing 2 L artificial seawater medium supplemented with 1 mM ammonium. All bottles and media were acid-cleaned and treated with Chelex resin to remove trace metal contaminants, and all manipulations were performed under HEPA-filtered conditions to minimize contamination. Cultures were acclimated to experimental conditions (23, 27, and 32 °C; low Fe: 250 nM; high Fe: 1250 nM) for at least six growth cycles prior to measurements. Three biological replicates were established for each treatment.

Carbon fixation rates were determined using 14C-labeled bicarbonate incorporation. Briefly, 45 mL culture subsamples were amended with 14C-NaHCO3 and incubated for 4 hours in the dark. Incubations were terminated by filtration onto 0.1 μm polyethersulfone filters (25 mm), and radioactivity was quantified using liquid scintillation counting.

Particulate organic carbon (POC) was measured by filtering 100–200 mL of culture onto precombusted glass fiber filters (GF75, 0.3 μm), followed by drying (~60 °C) and analysis using an elemental analyzer calibrated with organic standards.

Cellular iron quotas were determined under trace metal clean conditions. Culture samples (200–400 mL) were filtered onto acid-cleaned 0.1 μm polyethersulfone filters and rinsed with EDTA-oxalate to remove extracellular metals. Filters were stored at −20 °C prior to digestion. Samples were digested in 50% nitric acid at 90 °C for 2–3 days, dried, and re-dissolved in 0.1 M HNO3 with indium as an internal standard. Iron concentrations were measured using inductively coupled plasma mass spectrometry (ICP-MS).

Iron use efficiency (IUE) was calculated as the ratio of carbon fixation rate to cellular iron quota.