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Oscillatory dynamics in a bacterial cross-protection mutualism
Eugene Anatoly Yurtsev1, Arolyn Conwill1, Jeff Gore2
1Physics of Living Systems, Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139.
Summary
Microbial cooperation helps bacteria survive antibiotics. Two Escherichia coli strains formed a mutualism, protecting each other against ampicillin and chloramphenicol, enabling survival in harsh environments.
Area of Science:
- Microbiology
- Evolutionary Biology
- Ecology
Background:
- Microbial cooperation is crucial for survival in challenging environments.
- Antibiotic resistance in bacteria often involves cooperative antibiotic deactivation.
- Understanding cooperative antibiotic resistance is vital for clinical and ecological contexts.
Purpose of the Study:
- To investigate cooperative antibiotic deactivation in bacterial populations exposed to multiple antibiotics.
- To examine the population and evolutionary dynamics of cooperating bacterial strains.
- To determine the conditions under which cooperative antibiotic resistance is beneficial or detrimental.
Main Methods:
- Co-culturing two strains of Escherichia coli in the presence of ampicillin and chloramphenicol.
- Implementing daily dilutions of the bacterial coculture to observe population dynamics.
- Analyzing the relative abundance of the two strains over time under varying antibiotic concentrations.
Main Results:
- Two E. coli strains formed a cross-protection mutualism, surviving antibiotic concentrations lethal to individual strains.
- Daily dilutions induced large oscillations in strain abundance, varying by four orders of magnitude.
- Mutualism promoted long-term survival at moderate antibiotic levels but led to population collapse at higher concentrations.
Conclusions:
- Cooperative antibiotic deactivation can create stable cross-protection mutualisms between bacterial strains.
- Population dynamics, including oscillations, are significantly influenced by antibiotic concentrations and cooperative interactions.
- These findings suggest that similar microbial mutualisms may emerge during antibiotic treatments and in natural settings like soil.
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