Function of a Principal Na <sup>+</sup> /H <sup>+</sup> Antiporter, ShaA, Is Required for Initiation of Sporulation in <i>Bacillus subtilis</i>
Bibliographic record
Abstract
ShaA (sodium/hydrogen antiporter, previously termed YufT [or NtrA]), which is responsible for Na(+)/H(+) antiporter activity, is considered to be the major Na(+) excretion system in Bacillus subtilis. We found that a shaA-disrupted mutant of B. subtilis shows impaired sporulation but normal vegetative growth when the external Na(+) concentration was increased in a low range. In the shaA mutant, sigma(H)-dependent expression of spo0A (P(S)) and spoVG at an early stage of sporulation was sensitive to external NaCl. The level of sigma(H) protein was reduced by the addition of NaCl, while the expression of spo0H, which encodes sigma(H), was little affected, indicating that posttranscriptional control of sigma(H) rather than spo0H transcription is affected by the addition of NaCl in the shaA mutant. Since this mutant is considered to have a diminished ability to maintain a low internal Na(+) concentration, an increased level of internal Na(+) may affect posttranscriptional control of sigma(H). Bypassing the phosphorelay by introducing the sof-1 mutation into this mutant did not restore spo0A (P(S)) expression, suggesting that disruption of shaA affects sigma(H) accumulation, but does not interfere with the phosphorylation and phosphotransfer reactions of the phosphorelay. These results suggest that ShaA plays a significant role at an early stage of sporulation and not only during vegetative growth. Our findings raise the possibility that fine control of cytoplasmic ion levels, including control of the internal Na(+) concentration, may be important for the progression of the sporulation process.
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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) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".