In laboratory flasks containing just two teaspoons of media, scientists document how rapid adaptation between bacteria and viruses produce complex ecological networks. Credit: Josh Borin, UC San Diego
Key points:
- After just 3 weeks in a small closed laboratory flask, an accelerated evolutionary arms race between Escherichia coli bacteria and viruses resulted in several generations of evolutionary adaptations.
- As bacteria and viruses underwent co-evolution, repeating patterns of evolutionary development occurred, including nestedness and modularity.
- Virus phages and bacteria can be used as a model system to understand general evolutionary principles.
Darwin conceived evolution as a slow, gradual process during which species inherit adaptations incrementally over generations. However, today’s biologists have developed a method to observe evolutionary changes on much more accelerated timescales.
In a study, published in Science, researchers put Escherichia coli bacteria and viruses together in a small closed laboratory flask to study coevolution in real time. As viruses infect bacteria, the bacteria evolve new defensive measures to combat these attacks. In turn, viruses counter bacteria’s adaptations with their own evolutionary changes to evade any defensive measures.
After just three weeks in the flask, the accelerated evolutionary arms race resulted in several generations of evolutionary adaptations.
“We see how coevolution between bacteria and phage drive the emergence of a highly complicated ecological network,” explained Justin Meyer, professor at UC San Diego. “Evolution doesn’t have to be slow and gradual as Darwin thought.”
As bacteria and viruses adapted to each other over time, two evolutionary patterns emerged. First, they exhibited nestedness in which narrow interactions between bacteria and virus specialists are “nested” within a broader range of generalist interactions. Additionally, there was modularity such that interactions between species form modules within specialized groups, but not between groups.
This research offers new insight into how intricate ecological networks develop across disparate ecosystems ranging from food webs in the savanna to microbes in the ocean. Scientists can also use these perspectives on microbial evolution to reframe treatment in the face of SARS-CoV-2 virus adaptations in response to antibodies and vaccines.
“We show that evolution can produce complex ecological networks quickly from very little external help,” said Meyer. “So we can use phage and bacteria as a model system to understand general evolutionary principles and help show how life on Earth has evolved into such diverse and complex ecosystems from simple beginnings.”