Biofilms Confer Resistance to Simulated Extra-terrestrial Geochemical Extremes
Bibliographic record
Abstract
1 A bstract Biofilms improve microbes’ resistance to a variety of extreme physical and chemical conditions on Earth. The discovery of putative aqueous environments on other planetary bodies such as Mars motivates an interest in understanding the viability of life, and the potential role of biofilms, in previously unexplored geochemical extremes. We investigated the loss of viability of planktonic cells and biofilms of Sphingomonas desiccabilis (a Gram-negative, desiccation resistant, soil crust-forming organism) to simulated Martian brines. These brines were produced from geochemical modelling of past aqueous environments on Mars, and their high sulfate concentrations make them different to most terrestrial brines, although similar briny environments have been found in locations such as the Basque Lakes in Canada or in deep subsurface groundwater systems. Biofilms grown on basaltic scoria were subjected to the simulated martian brines and the viability of cells was measured over time and compared to equivalent planktonic cultures. Crystal violet assay was used to measure how the biomass of the biofilms changed over time in response to the brines. While certain brines were highly hostile to microbial viability, we found that biofilms that were desiccated prior to being treated with brines maintained viability over a longer treatment period when compared to planktonic cells. Our results show that biofilms confer short-term protection to the harsh osmotic, ionic, and acidic conditions of Mars-relevant brines. However, in the most extreme simulated brines, even biofilms eventually lost viability. By demonstrating that biofilms confer protection to conditions that are potentially analogous to current day recurrent slope lineae (thought to be produced by the flow of briny fluids) on Mars, our results show that contaminant biofilm-forming microorganisms may have a greater chance of surviving in so-called ‘Special Regions’ on Mars, with implications for planetary protection in missions that aim to explore these regions.
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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 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| 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".