Is *Candidatus* (*Ca.*) Desulforudis audaxviator-style self-sufficiency in the Bacillota_B deep-anchor cohort or absent from the cultured cohort?

Two projects disagree on whether Ca. Desulforudis audaxviator, the lineage that exemplifies extreme biosynthetic self-sufficiency in the deep subsurface, belongs to the genome cohorts they analysed. The Bacillota_B report lists one of this organism’s genomes in its anchor cohort and reads deep-clay gene-content expansion as consistent with self-sufficiency. ₁ The clay report states that its cultured cohort does not include such extreme self-sufficient lineages. _1,2 The disagreement bears on how far cultured-genome results represent self-sufficient lineages, the question of biosynthetic-self-sufficiency-and-cultivation. The corpus does not currently settle it.

Evidence Sides

Side A: the self-sufficient lineage is in the anchor cohort, and the expansion is read as consistent with self-sufficiency

• The Bacillota_B report finds gene-content expansion, opposite in direction to the “small is mighty” streamlining finding of Tian et al. (2020). ₁
• The report limits Tian’s claim to the Patescibacteria/CPR (Candidate Phyla Radiation) superphylum, with ≤1 Mbp (million base pairs) genomes and an episymbiotic lifestyle (living attached to a host’s surface). Bacillota_B are anaerobic Firmicutes that grow free-living rather than as episymbionts. ₁
• The report reads the expansion as consistent with the Beaver & Neufeld (2024) self-sufficiency hypothesis. ₁
• It lists Ca. Desulforudis audaxviator genome GB_GCA_020725505.1 in its anchor cohort; Becraft et al. (2021) showed this genome retains full nitrogen fixation, amino-acid biosynthesis and carbon fixation, with no streamlining. ₁

Side B: the cultured cohort lacks the extreme self-sufficient lineages

• The clay report states that the cultured cohort does not include the extreme self-sufficient lineages that Ca. Desulforudis audaxviator exemplifies. _1,2

Cohort definitions differ

• The two reports define their deep anchor cohorts differently: 10 deep-clay Bacillota_B genomes versus 9 unfiltered deep anchors. _1,2
• The Bacillota_B cohort also includes metagenomic genomes and rock-porewater MAGs (metagenome-assembled genomes, which are reconstructed from environmental sequence rather than from isolates). _1,2
• The corpus does not establish how GB_GCA_020725505.1 was recovered. It also does not report how this genome scored on GapMind, a tool that predicts whether biosynthetic pathways are complete. _1,2

Possible Reconciliations

• Hypothesis 1: the cohorts differ in composition. The Bacillota_B anchor cohort also includes metagenomic genomes and rock-porewater MAGs, while the clay report’s statement concerns a cultured cohort. _1,2 On this reading, both statements could hold for their own cohorts.
• Hypothesis 2: cohort membership differs. The genome may fall inside one anchor definition and outside the other, for example if one cohort is filtered by habitat or recovery method and the other is not.
• Hypothesis 3: the expansion has another source. The expansion may come from lineages other than Ca. Desulforudis audaxviator, making the Becraft et al. (2021) citation supporting context rather than evidence drawn from the cohort.

Resolving Work

• Recovery method: Retrieve assembly metadata for GB_GCA_020725505.1 in the KBase Data Lakehouse and classify it as isolate, MAG or single-cell genome, to show whether it can belong to a cultured cohort.
• Cohort overlap: Compare the 10 deep-clay Bacillota_B genomes against the 9 unfiltered deep anchors by set overlap, to show which genomes sit in both cohorts.
• GapMind scoring: Score GB_GCA_020725505.1 with GapMind alongside the clay cohort, to show whether it appears self-sufficient under the clay report’s pathway criteria.
• Expansion in verified isolates: Recompute the Bacillota_B gene-content expansion restricted to genomes with verified isolate provenance, to show whether the expansion holds within cultured genomes.