Light-harvesting by antenna-containing xanthorhodopsin from an Antarctic Pseudanabaenaceae cyanobacterium
Bibliographic record
Abstract
Microbial rhodopsins are light-sensitive proteins vital to various phototrophic and sensory processes in microorganisms. Xanthorhodopsins, with their dual chromophore system involving retinal and carotenoids, have been predominantly studied in the extreme halophilic bacterium Salinibacter ruber and in the early-branching thylakoid-less cyanobacterium Gloeobacter violaceus, where they facilitate light-driven outward proton pumping. However, their distribution, binding specificity, and ecological significance in cyanobacteria remain poorly understood. Here we report the incidence of xanthorhodopsin genes in cyanobacterial genomes and characterize psXR, a xanthorhodopsin from an uncultured Antarctic cyanobacterium from the filamentous family of Pseudanabaenaceae that binds a hydroxylated carotenoid antenna. Through bioinformatic, spectroscopic, functional and structural analyses, we determine the properties of psXR and potential physiological roles of cyanobacterial xanthorhodopsins. Our findings suggest xanthorhodopsins' role in modulating light-harvesting efficiency in cyanobacteria, particularly in extreme environments. The antenna binding and associated structural changes likely provide selective advantages for adapting to polar light conditions such as prolonged low light intensities and spectral shifts, contributing to cyanobacterial survival in harsh habitats.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".