Free tools Windows power users keep installed
One-click scans. No signup required.
In a 2020 laboratory study, Escherichia coli grew in ampicillin when cultured alongside Bacillus subtilis, even though it was sensitive to the drug when grown alone. Meanwhile, B. subtilis—the comparatively tolerant species in isolation—could not grow in the mixed culture. The reversal reflected a change in the bacteria’s shared drug environment, not newly acquired genetic resistance.
What changed when the bacteria were cultured together?
Leticia Galera-Laporta and Jordi Garcia-Ojalvo compared non-resistant strains of B. subtilis and E. coli exposed to moderate concentrations of ampicillin, a β-lactam antibiotic. They tested each species alone and the two together under controlled laboratory conditions.
As an Amazon Associate I earn from qualifying purchases.
| Culture condition | B. subtilis response | E. coli response |
|---|---|---|
| Grown alone with ampicillin | Comparatively tolerant | Sensitive |
| Grown together with ampicillin | Could not proliferate | Could proliferate |
Thus, the pattern seen in monoculture reversed in coculture: the species that had been more sensitive alone could grow in the mixed population, while the comparatively tolerant species could not. The authors’ mathematical model, constrained by the species’ responses when tested separately, predicted this antithetic population response.
How could one species benefit while the other loses?
The authors attributed the reversal to differences between the species in how effectively they inactivated ampicillin. When both were present, those differences altered how much active drug was available to each population. The relevant context was therefore not just a bacterium’s response to ampicillin in isolation, but the drug environment created by the community.
This is a population-level change in growth under the tested conditions. As the authors explain, “what changes here is not the molecular sensitivity of the bacteria to the antibiotic … but rather their collective response to the drug,” because the presence of another bacterial type changes drug availability for each. The full study describes the result and its proposed mechanism.
Does this mean E. coli evolved antibiotic resistance?
No. The experiment does not show that E. coli acquired a genetic mutation or became intrinsically resistant during the study. It shows that its population could proliferate in a particular mixed culture where the shared antibiotic environment differed from the one in a monoculture. Calling that a change in intrinsic drug sensitivity would confuse the bacteria’s underlying sensitivity with their collective growth response.
Rank #2
- Great extension activities for science and biology
- Correlated to standards
- Comprehensive biology vocabulary study
- Fascinating true-to-life illustrations
What does the result mean beyond this experiment?
The study shows why a single-species test may not fully predict what happens when different bacteria encounter an antibiotic together: interactions can change the drug available in the community. That is a reason for caution when interpreting isolated-species results, not a general rule that one bacterium will protect another.
Recommended Free Tools
The work tested one pairing, one antibiotic, and specified strains and laboratory conditions. It does not establish that the same effect occurs in human infections, including infections involving multiple species, or that introducing one species could safely alter another’s response to treatment. It is not evidence for using a probiotic or any other intervention to manipulate antibiotic response. The findings were reported by Galera-Laporta and Garcia-Ojalvo in Science Advances on March 6, 2020.
Quick Recap
Best Value
Rank #3
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
