| Claim/Topic | Key findings (include quantitative values) | Evidence type | Source (full citation short) | Publication date | URL |
|---|---|---|---|---|---|
| Target identity verification | In *Nitrososphaera viennensis* EN76, **ureC / NVIE_014740** is explicitly identified as the **urease alpha subunit**; it is reported in the same operon as a urea transporter gene **ut / NVIE_014780**, matching UniProt A0A060HK93 annotation (pqac-00000000, pqac-00000001) | Transcriptomics / genome-linked annotation | Qin et al., *Nat Microbiol* | Jan 2024 | https://doi.org/10.1038/s41564-023-01593-7 |
| Primary function and substrate preference in EN76 | *N. viennensis* uses urea as an alternative N/energy source precursor but **prefers ammonia over urea**: apparent **Km(app)** for ammonia **0.68 ± 0.16 µM** versus urea **8.97 ± 1.27 µM**; specific affinity for urea is ~**10-fold lower** than for ammonia (pqac-00000000, pqac-00000012, pqac-00000021) | Culture kinetics | Qin et al., *Nat Microbiol* | Jan 2024 | https://doi.org/10.1038/s41564-023-01593-7 |
| Regulation of ureC1 by nitrogen source | After substrate switching, **ut** and **ureC (NVIE_014740)** transcripts changed by about **10-fold within 24 h**: induced after urea addition and reduced after ammonia addition; by contrast **amt1** remained similar (**1,379 TPM on ammonia vs 1,348 TPM on urea; P = 0.84**) (pqac-00000000, pqac-00000001) | Transcriptomics | Qin et al., *Nat Microbiol* | Jan 2024 | https://doi.org/10.1038/s41564-023-01593-7 |
| Physiological switching behavior | Urea-grown EN76 showed immediate O2 consumption when low urea (**10–20 µM**) or ammonia (**20–40 µM**) was added, but ammonia-grown cells given **10 µM urea** showed no immediate O2 uptake until after ammonia depletion, indicating repression of urea use during ammonia growth; EN76 maintained growth without a pronounced lag during transition (pqac-00000002, pqac-00000010) | Physiology / microrespirometry | Qin et al., *Nat Microbiol* | Jan 2024 | https://doi.org/10.1038/s41564-023-01593-7 |
| Cellular role of urea in EN76 | NanoSIMS-based single-cell data indicate AOM use urea mainly as an **N source rather than C source**; in soil AOA *N. viennensis*, urea-derived C was only ~**0.1%** during ammonia growth, increasing to **0.5–1.1%** after urea depletion, while bicarbonate-derived C remained much larger (**13 ± 4.5% → 8.0 ± 3.5%**) (pqac-00000018) | Single-cell isotope tracing | Qin et al., *Nat Microbiol* | Jan 2024 | https://doi.org/10.1038/s41564-023-01593-7 |
| Localization of urease system | Across tested ammonia oxidizers including EN76, **no extracellular urease activity** was detected; no **signal peptides** were found in urease genes and no nearby secretion-system genes were found, supporting **cytoplasmic localization** of urease/ureC1 (pqac-00000004, pqac-00000008, pqac-00000011) | Enzyme assay + comparative genomics | Qin et al., bioRxiv | Aug 2023 | https://doi.org/10.1101/2023.08.04.551995 |
| Broader AOA genomic context | Review/genomic survey of **70 nitrifier genomes** found urea to be the most commonly encoded LDON substrate; AOA generally carry **ureABC** plus **ureDEFG** and use archaeal transporter types **dur3** and/or **utp** rather than bacterial **urtABCDE**; experimental urea use is confirmed for **N. viennensis EN76** (pqac-00000005, pqac-00000020) | Comparative genomics / review | Liu et al., *Front Microbiol* | Dec 2023 | https://doi.org/10.3389/fmicb.2023.1273211 |
| Initial discovery of urease capacity in EN76 | Draft genome of EN76 contained a contig with a **potential urease operon/urease gene cluster**, leading the authors to propose that this soil AOA could use **urea instead of ammonia as sole energy source**; this provided the first genome-based indication for ureC1 function in this organism (pqac-00000006, pqac-00000007) | Genomics / culture characterization | Tourna et al., *PNAS* | Apr 2011 | https://doi.org/10.1073/pnas.1013488108 |
| Soil archaeal prevalence of urease potential | Across 12 major soil Nitrososphaeria lineages, **85.7–89.8%** of AOA in surveyed soils were estimated to encode **urease** (based on **ureC** relative to **amoA/rpoB**), indicating urea use is widespread among soil archaeal nitrifiers related to *Nitrososphaera* (pqac-00000020) | Soil metagenomics / expression-focused ecology | Zhao et al., *ISME J* | Aug 2023 | https://doi.org/10.1038/s41396-023-01493-y |
| Environmental significance of archaeal ureC | In dark-ocean metagenomes, **ureC** occurred in **39%** of deep-sea cells regionally and **10–46%** globally (median ~**36%**); on average **25%** of deep-sea cells assimilated urea-derived N (or **60%** of active cells), and urea-based nitrification occurred at all sampled depths at one site (pqac-00000013, pqac-00000014, pqac-00000015, pqac-00000016) | Environmental metagenomics + rates | Arandia-Gorostidi et al., *ISME J* | Jan 2024 | https://doi.org/10.1093/ismejo/wrae230 |
| Quantitative urea contribution to marine nitrification | Southern Ocean data showed Thaumarchaeota-associated **ureC** abundance was variable (highest mean **1.2 × 10^6 copies L^-1** in CDW); mean **ureC/rrs ~0.14** overall. Ammonia oxidation averaged **10.9 nmol L^-1 d^-1** versus urea oxidation **2.6 nmol L^-1 d^-1** (or **1.5** excluding outliers), suggesting urea makes a significant but smaller, context-dependent contribution to nitrification (pqac-00000017) | Environmental rates + qPCR/metagenetics | Hollibaugh et al., preprint/2023 study | 2023 | URL not available in retrieved context |


*Table: This table compiles organism-specific and ecosystem-level evidence relevant to ureC1 (NVIE_014740) in *Nitrososphaera viennensis* EN76, emphasizing verified identity, biochemical role, regulation, localization, and recent quantitative findings from 2023–2024 literature.*