MODEL BOUNDARY
A working hypothesis,
open to inspection.
This atlas transcribes Chapter 14, pp. 498–506, of Otangelo Grasso’s X-ray of Life: Volume III (2024). The thermophilic carbon-fixing scenario follows pp. 546–550. The cell is hypothetical; the catalogue combines examples from different organisms.
Working scenario: host-independent growth in an inorganic nutrient environment, with CO₂, a suitable electron donor and acceptor, nitrogen, phosphorus, sulfur, and trace metals supplied. A single compatible carbon-fixation route, respiratory scheme, membrane chemistry, and complete biosynthetic inventory still need selection and validation.
Free-living does not mean independent of the environment. This is neither a reconstructed ancestral cell nor an experimentally demonstrated minimum.
What the connections mean
System and group edges are curator-proposed functional dependencies. An arrow runs from a provider to a recipient. It does not imply physical binding or experimentally established essentiality.
The protein-association layer contains selected relationships described in the book (pp. 302, 315). Solid edges denote reported association; dashed edges denote co-complex membership without asserting a specific pairwise contact. No binding kinetics, structural coordinates, or species-matched interactome are supplied.
SOURCE ACCOUNTING
Make the counts inspectable.
Chapter 14 reports a base subtotal of 1,134, then adds 81 complex subunits to reach 1,215. The book’s own Note 1 assumes those subunits are “not double-counted in their respective categories”, and that assumption does not hold: category 9 is printed at 124 proteins and cannot exclude the 54 ribosomal proteins. 1,215 is therefore inflated by 81, and 1,134 is the figure that survives of the two. The 233 detailed rows sum to 1,155 mixed units, and the gap against 1,134 is not diffuse: the table below locates it in a handful of categories — chiefly Transport Systems, Metal Cluster Assembly and Amino Acid Metabolism — where the printed subtotal is lower than the groups it is said to total.
Neither 1,134 nor 1,155 is a deduplicated protein count. The book counts group memberships; a genome annotation counts genes. Chapter 14 never claims to inventory a specific organism, so 1,134 and the 1,553 annotated proteins of A. aeolicus are not commensurable and are never subtracted from one another. The 1,066 figure quoted in earlier drafts does not appear in the book at all. The book’s 702,700 aa total is also withdrawn here: it exceeds the entire real proteome of A. aeolicus (488,954 aa across all 1,553 proteins) while claiming 338 fewer proteins, and implies a mean length of 578 aa against a real mean of 315.
Where the category boundaries are unambiguous the two routes agree closely: Amino Acid Metabolism 98 against 95 retained, Nucleotide Metabolism 51 against 47, Lipid and Membrane Metabolism 51 against 52. That independent agreement is the best support for the order of magnitude, even where the bookkeeping does not hold.
Alternatives and context-dependent systems
The book includes both Wood–Ljungdahl and reductive TCA components, both mevalonate and MEP pathways, aerobic respiratory complexes alongside anaerobic metabolism, and repeated signaling and homeostasis groups. These should not automatically be combined into a minimal single organism.
Quorum sensing, HGT, extensive defense, specialized metal clusters, and host interactions are retained as source entries. Inclusion here does not establish universal necessity. The “nine enzymes” on p. 546 describe a proposed carbon-metabolism subset, not a complete self-reproducing cell.
Protein lengths and amino-acid totals are transcribed estimates, not verified sequences. For example, DnaK has differing reported lengths on pp. 212 and 302. Protein abundance, copy number, expression state, and gene identifiers are not available.
Research anchors & next validation
Hutchison et al. (2016) · Design and synthesis of a minimal bacterial genome ↗
Environmental conditions shape the nature of a minimal bacterial genome (2019) ↗
These experimental models give context, not validation of this hypothetical cell. Minimal requirements depend on nutrient availability and growth conditions.
Three of those next steps are now done. A reference organism and environment were chosen (Aquifex aeolicus VF5; H₂/O₂, CO₂ via the reductive TCA cycle, 95 °C, chemically defined medium), each required function was mapped to nonredundant gene products with accessions, and the alternative pathways were reconciled — giving 912 proteins individually justified, 303 removed with a stated reason each, and 338 left undetermined. That inventory is under Minimal proteome ↗.
What remains: flux-balance analysis, to test whether the 303 removals are jointly tolerable rather than only individually defensible; and a genetic system for A. aeolicus, which has none. No gene in this genome has ever been deleted, so experimental essentiality categories are empty — 0 of 1,553 — and quantitative growth or knockout predictions still require a validated metabolic model.
Version 02 · Source-grounded exploratory atlas · 24 October 2026