Temporal effects on the composition of a population of <i>Sinorhizobium meliloti</i> associated with <i>Medicago sativa</i> and <i>Melilotus alba</i>
Bibliographic record
Abstract
An assessment was made of the impact of temporal separation on the composition of a population of Sinorhizobium meliloti associated with Medicago sativa (alfalfa) and Melilotus alba (sweet clover) grown at a single site that had no known history of alfalfa cultivation. Root nodules were sampled on six occasions over two seasons, and a total of 1620 isolates of S. meliloti were characterized on the basis of phage sensitivity using 16 typing phages. Plant infection tests indicated that symbiotic S. meliloti were deficient in the soil at the time of planting and that these bacteria were present at low density during the first season (<10(2)/g of soil); in the second season numbers increased markedly to about 10(5)/g of soil. Overall, 37 and 51 phage types, respectively, were encountered among the nodule isolates from M. sativa and M. alba. The data indicate significant temporal shifts in the frequency and diversity of types associated with the two legume species. Apparent temporal variation with respect to the frequency of types appeared largely unpredictable and was not attributable to any one sampling time. The results indicate an apparent reduction in phenotypic diversity over the course of the experiment. Differential host plant selection of specific types with respect to nodule occupancy was indicated by significant interactions between legume species and either the frequency or diversity of phage types. Isolates from M. sativa that were resistant to lysis by all typing phages (type 14) were unusual in that they were predominant on this host at all sampling times (between 53% and 82% nodule occupancy) and were relatively homogeneous on the basis of DNA hybridization with 98% of the isolates analysed sharing the same nod EFG hybridization profile. In contrast, those isolates from M. alba comprising type 14 were encountered at low total frequency (2%) and were genetically heterogeneous on the basis of Southern hybridization. The implications of the observed temporal and host plant variation for ecological studies are discussed.
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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 | 0.001 |
| 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 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".