The species of **bacteria** in a **Wisconsin lake** are constantly evolving in an endless cycle from which they do not seem to be able to escape.
According to a new study published in Nature Microbiology, researchers found that, over the course of a year, most of the individual bacteria species in Lake Mendota **evolve rapidly** in response to the dramatic **seasonal changes**.
Bacteria: rapid evolution and repetitive cycle
The **genetic variants** of the bacteria increased and decreased over generations, but hundreds of species reverted to nearly identical copies of what they had been genetically before about a thousand generations of evolutionary pressures.
**Individual microbes** have a lifespan of only a few days, so scientists compared **bacterial genomes** to examine changes in the species over time. This seasonal change repeated year after year, as if evolution were a movie that repeated itself over and over.
Research and key findings
“I was surprised that such a large portion of the **bacterial community** was experiencing this kind of change,” said Robin Rohwer, a postdoctoral researcher at the University of Texas (UT) in Austin. Rohwer led the research, first as a doctoral student at the University of Wisconsin-Madison and then at UT.
Lake Mendota undergoes significant changes from one season to another: during winter, it is covered in ice, and during summer, **it is covered in algae**. Bacterial strains that adapt best to a set of environmental conditions outcompete other strains during one season, while other strains thrive in different seasons.
Unique temporal series of metagenomes
The team used a unique archive of 471 **water samples collected** over 20 years from Lake Mendota by McMahon, Rohwer, and other UW-Madison researchers.
For each water sample, they assembled a metagenome, all the **genetic sequences** of DNA fragments left by bacteria and other organisms. This resulted in the longest temporal series of **metagenomes** ever collected from a natural system.
“This study is a radical shift in our understanding of how **microbial communities** change over time,” said Brett Baker, a study co-author. “This is just the beginning of what these data will tell us about microbial ecology and evolution in nature.”
Have you checked out our YouTube channel yet? Subscribe now!
