Integration of planktonic bacteria in the biofilm and functional analysis of the Bthur62720 gene in Bacillus thuringiensis
Bibliographic record
Abstract
Bacillus thuringiensis is able to produce a pellicle at the air-liquid interface in glass tubes under static conditions. During biofilm formation, two populations coexist: a sessile floating population and a planktonic population, located in the culture medium beneath the pellicle. Using spectrophotometric measurements, we followed the growth of both populations during the B. thuringiensis 407 pellicle formation. Our results show that while the biofilm biomass increases rapidly, the planktonic population growth drops sharply. This decrease is not observed with the 407 spoOA mutant or for strains unable to form a biofilm, and cannot be attributed to cell lysis or cell sedimentation. Therefore, it is the result of a massive integration of planktonic cells in the preformed pellicle. We also visualized, using epi-fluorescence microscopy, the integration of planktonic bacteria of the 407 strain in its preformed biofilm. The recruited cells are located in restricted areas of the biofilm, where the density of sessile cells is low, revealing a heterogeneous spatial distribution of the immigrant cells within the biofilm. To identify the mechanisms involved in the recruitment of planktonic cells in the biofilm, we screened a bank of mutants of the 407 strain, obtained by random mutagenesis, for their ability to integrate a pre-existing biofilm. One of the mutants in the library is strongly affected in its ability to integrate a biofilm. This deficiency is caused by the disruption of the Bthur62720 gene, which is carried by the BTB-9p plasmid and encodes a 21 kDa protein. This protein has no homolog and in silico analysis predict a signal peptide, a N-terminal domain of unknown function and a C-terminal membrane domain. Using immunocytochemistry and translational fusion assays with GFP, we showed that this protein is parietal, polar and that its N-terminal domain is cytoplasmic. With a specific dye of charged membrane phospholipids, 10-N-nonyl acridine orange, we showed that the deletion of Bthur002_62720 disorganizes the lipid rafts distribution, which appear essentially polar in wild type strain 407. Moreover, this deletion strongly affects linear swimming, but not bacterial tumbling or the presence of flagella. These results allow us to hypothesis that Bthur62720 stabilizes the lipid rafts located at the cell poles. The polar localization of these rafts, required for the clustering of chemoreceptors, would be necessary to ensure a normal chemotaxis function and thus, bacterial swimming.
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 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) | 0.001 | 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".