The interplay between glucose and aromatic compound regulation by two IclR-type transcription factors, LigR1 and LigR2, in <i>Pseudomonas putida</i> KT2440
Bibliographic record
Abstract
Abstract The rhizosphere is a hotspot of microbial activity where plants release a diverse array of aromatic compounds, including shikimate pathway intermediates and monolignols. Pseudomonas putida KT2440, renowned for its metabolic versatility in this niche, uses largely uncharacterized regulatory and enzymatic strategies to utilize these compounds. We investigated two IclR-type transcriptional regulators, LigR1 and LigR2, that control expression of the uncharacterized lig1 and lig2 operons. We demonstrate that ligR1 deletion caused growth defects on glucose and 4-hydroxybenzoate accompanied by cell elongation and aggregation. Structural and functional analyses reveal that LigR1 and LigR2 activate the lig1 operon but repress the lig2 operon. LigR1 binding of 4-hydroxybenzoate induced repression by triggering tetramerization and increasing DNA-binding activity. In contrast, LigR2 responded to quinate, protocatechuate and 4-hydroxybenzoate to potently induce lig2 operon expression by relieving repression. While both operons cooperate in metabolizing these compounds, we propose the lig1 operon mediates influx through its major facilitator superfamily (MFS) transporter (PP_2604), whereas the lig2 operon catalyzes breakdown via a protocatechuate intermediate and the meta-cleavage pathway, supplying oxaloacetate to the TCA cycle. Importantly, we show that P. putida repurposes shikimate pathway intermediates for energy production. These findings challenge the canonical biosynthetic view of the shikimate pathway and redefine the metabolic flexibility of soil pseudomonads. We reveal a novel mechanism enabling P. putida to thrive in the chemically complex rhizosphere and open new avenues for exploring alternate roles of the shikimate pathway, emphasizing transcriptional regulators as tools to deconvolute complex metabolic landscapes. Highlights LigR1 and LigR2 transcriptionally regulate the lig1 and lig2 operons Lig1 operon is required for import of glucose and shikimate-derived compounds Lig2 operon metabolizes shikimate pathway compounds Dysregulated LigR1/LigR2 expression impacts bacterial physiology Graphical Abstract
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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) | 0.000 | 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".