Differentiating <i>Bacillus subtilis</i> incorporates valine and methionine carbon into the backbone of specific fatty acids
Bibliographic record
Abstract
Summary Sporulation in Bacillus subtilis has long been a model of cellular differentiation, many aspects of which are well understood. The early stage of this process is of particular interest, especially the interrelationship of regulatory processes with metabolism in response to environmental changes. We analyzed cellular fatty acids as their methyl esters using capillary gas chromatography coupled to mass spectrometry during the transition from vegetative growth to early sporulation phase. Measurement of changes in the content of heavy fatty acid analogs in cultures supplemented with deuterium-labeled valine or methionine, or 13 C-labeld valine, showed that label was incorporated into the backbone of 12-methyltridecanoic and 14-methylpentadecanoic acid, in both sporulating and Δspo0A cultures. These fatty acids were formed starting with isobutyryl-CoA apparently originating only from L -valine-d 8 in cultures so supplemented. Our observations indicate that following vegetative growth a pathway exists from certain amino acids into fatty acid methylene groups, evidently passing through propionyl-CoA. This finding has the potential to deepen understanding of the metabolic basis of cellular differentiation and identify new targets for antibiotics. We also observed a significant, continuous increase in the proportion of 13-methyltetradecanoic acid in fatty acids during the same period in which the pre-spore membrane would be formed. Graphical abstract: Abbreviated Summary Early in at least some Bacillus subtilis differentiation scenarios, a straight-chain metabolite derived from propionyl-CoA is incorporated into fatty acids primed with isobutyryl-CoA possibly derived from cellular protein valine. Concurrently a leucine related fatty acid increases significantly, potentially comprising the predominant pre-spore septum fatty acid component. These processes occur in conjunction with the onset of fatty acid β-oxidation and bulk protein turnover.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.044 | 0.005 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".