Temporary loss of antibiotic resistance by marked bacteria in the rhizosphere of spruce seedlings
Bibliographic record
Abstract
Survival and persistence of two plant growth-promoting rhizobacteria strains in the rhizosphere of young spruce seedlings were evaluated in field plots and soil microcosms. Bacillus polymyxa strain Pw-2R and Pseudomonas fluorescens strain Sw5-RN are spontaneous antibiotic-resistant derivatives of the naturally occurring parental strains B. polymyxa Pw-2 and P. fluorescens Sw5, respectively. Resistance to 200 microg ml(-1) rifamycin in strain Pw-2R, and to 100 microg ml(-1) each of rifamycin and nalidixic acid in Sw5-RN, facilitated monitoring of these bacteria in rhizosphere samples. Strains Pw-2R and Sw5-RN were each inoculated into the rhizosphere of spruce seedlings in field plots as well as in intact soil core microcosms that were incubated under controlled environmental conditions. Bacterial survival data based on the abilities of Pw-2R and Sw5-RN to be re-isolated from rhizosphere samples, and by growing on agar containing antibiotics, were collected over a 2-year period as part of a larger study. The population sizes of both bacterial strains appeared to drop below detection limits by the beginning of the second year as they failed to grow on primary isolation media containing antibiotics. However, strains Pw-2R and Sw5-RN grew on isolation medium with antibiotics if they were first isolated on agar without antibiotics and then replica-plated onto agar media containing antibiotics. A similar temporary loss of antibiotic resistance has been observed with endophytic bacteria, but our results suggest such masking may be of much wider significance than previously thought. If it commonly occurs in rhizosphere colonizing bacteria as well as endophytes, significant underestimates of bacterial population sizes in similar environmental samples may result.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 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 | 0.000 |
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 teacher head, 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".