Herbicidal Effects of Sulfamethoxazole in <i>Lemna gibba</i>: Using <i>p</i>-Aminobenzoic Acid As a Biomarker of Effect
Bibliographic record
Abstract
Sulfamethoxazole (SMX) is among the most frequently detected antibiotics in the environment, heavily used in both human therapy and agriculture. Like other sulfonamides, SMX disrupts the folate biosynthetic pathway in bacteria, which was recently established as identical to that of plants, raising concerns over nontarget toxicity. Consequently, Lemna gibba was exposed to SMX to evaluate phytotoxic potency and mode of action (MOA) by HPLC-MS/MS measurement of p-aminobenzoic acid (pABA) metabolite levels, a precursor to folate biosynthesis and substrate of the target enzyme dihydropteroate synthase (DHPS). pABA levels were found to increase upon exposure to SMX following an exponential rise to a maxima regression model in a concentration-dependent manner. The EC50 for pABA content was 3.36 microg/L, 20 times lower than that of fresh weight (61.6 microg/L) and 40 times lower than frond number (132 microg/L) responses. These results suggest that, as in bacteria, sulfonamide antibiotics specifically disrupt folate biosynthesis via inhibition of DHPS. Analysis of pABA concentrations appears to provide a sulfonamide-specific biomarker of effect based on MOA with exceptional diagnostic capacity and sensitivity compared to traditional morphological end points. Using the EC50 for pABA content, a potential hazard was identified for L. gibba exposed to SMX, which would not have been detected based upon traditional standardized morphological approaches.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.002 |
| Science and technology studies | 0.000 | 0.009 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| 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".