Overexpression of AdeIJK RND efflux pump in <i>Acinetobacter baumannii</i> using the mini-Tn <i> <b>7</b> </i> T-based single copy induction system can lead to <i> lacI <sup>q</sup> </i> mutation
Bibliographic record
Abstract
ABSTRACT Chromosomal gene complementation with inducible expression is a powerful approach for investigating bacterial gene function. The pUC18T-mini-Tn 7 T system enables isopropyl β-D-1-thiogalactopyranoside (IPTG)-inducible, site-specific genomic integration of genes in single copy via the P tac-lacI q regulatory system. While widely used, limitations remain underexplored. Here, we report a rare and possibly protein-specific but critical caveat of this system during overexpression of AdeIJK, a resistance-nodulation-division efflux pump, in Acinetobacter baumannii . IPTG exposure led to the emergence of IPTG-unresponsive mutants with the loss of IPTG-dependent gene expression. Sequencing identified a shared R197S mutation in lacI , impairing IPTG binding and derepression. These findings underscore the need for vigilant monitoring of regulatory elements when using inducible systems, particularly during the expression of genes whose overexpression is not well tolerated by bacteria. IMPORTANCE Genetic tools are essential for gaining deeper insights into bacterial systems. Though these tools have been of great value in the study of genotype-phenotype relationships, it is equally important to recognize their limitations. We believe this observation will help raise awareness of a potential constraint associated with the widely used mini-Tn7 gene expression system and enable researchers to avoid misinterpretation of experimental results. Being conscious of this limitation, subtle changes that may have otherwise gone unnoticed can be more effectively identified.
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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 | 0.001 |
| 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 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".