Two <i>rsaM</i> homologues encode central regulatory elements modulating quorum sensing expression in <i>Burkholderia thailandensis</i>
Bibliographic record
Abstract
Abstract The bacterium Burkholderia thailandensis possesses three conserved N -acyl- L -homoserine lactone (AHL) quorum sensing (QS) systems designated BtaI1/BtaR1 (QS-1), BtaI2/BtaR2 (QS-2), and BtaI3/BtaR3 (QS-3). These QS-systems are associated with the biosynthesis of N -octanoyl-homoserine lactone (C 8 -HSL), N -3-hydroxy-decanoyl-homoserine lactone (3OHC10-HSL), as well as N -3-hydroxy-octanoyl-homoserine lactone (3OHC 8 -HSL), which are produced by the LuxI-type synthase BtaI1, BtaI2, and BtaI3, and modulated by the LuxR-type transcriptional regulators BtaR1, BtaR2, and BtaR3. Both btaR1 / btaI1 and btaR2 / btaI2 gene clusters contain an additional gene that is conserved in the Burkholderia genus, homologous to a gene coding for the negative AHL biosynthesis modulatory protein RsaM originally identified in the phytopathogen Pseudomonas fuscovaginae , and hence designated rsaM1 and rsaM2 . We have characterized the function of these two rsaM homologues and demonstrated their involvement in the regulation of AHLs biosynthesis in B. thailandensis strain E264. We measured the production of C 8 -HSL, 3OHC 10 -HSL, and 3OHC 8 -HSL by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) in the wild-type strain and in the rsaM 1 - and rsaM 2 - mutants, and monitored the transcription of btaI 1, btaI 2, and btaI 3 using chromosomal mini-CTX- lux transcriptional reporters. The expression of btaR 1, btaR 2, and btaR 3 was also measured by quantitative everse-transcription PCR (qRT-PCR). We demonstrate that the QS-1 system is repressed by RsaM1, whereas RsaM2 principally represses the QS-2 system. We also found that both rsaM1 and rsaM2 are QS-controlled, as well as negatively auto-regulated. We conclude that RsaM1 and RsaM2 are an integral part of the QS modulatory circuitry of B. thailandensis , and play a major role in the hierarchical and homeostatic organization of the QS-1, QS-2, and QS-3 systems. Importance Quorum sensing (QS) is a global regulatory mechanism of genes expression depending on bacterial density. QS is commonly involved in the coordination of genes expression associated with the establishment of host-pathogen interactions and acclimatization to the environment. We present the functional characterization of the two rsaM homologues designated rsaM1 and rsaM2 in the regulation of the multiple QS systems coexisting in the non-pathogenic bacterium Burkholderia thailandensis , widely used as a model system for the study of the pathogen Burkholderia pseudomallei . We found that inactivation of these rsaM homologues, which are clustered with the other QS genes, profoundly affects the QS regulatory circuity of B. thailandensis . It is proposed that these genes code for QS repressors and we conclude that they constitute essential regulatory components of the QS modulatory network of B. thailandensis , and provide additional layers of regulation to modulate the expression of QS-controlled genes, including those encoding virulence/survival factors and linked to environmental adaptation in B. pseudomallei .
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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".