Seasons Shape Evolution: How Lake Mendota’s Bacteria Adapt in Endless Genetic Loops

 Lake Mendota in Wisconsin undergoes dramatic seasonal changes frozen in winter, blanketed with algae in summer. A groundbreaking study reveals how these shifts force bacteria into an evolutionary time loop.

Led by researchers at the University of Texas at Austin, the study examined 471 microbe samples collected over 20 years, tracking genetic changes across thousands of bacterial species. The findings? Microbes evolve rapidly only to revert back to their original genetic state as seasons cycle.

Key Discoveries:

✔ 80% of the 2,855 bacterial genomes studied showed cyclical evolution—adapting in summer, then reversing in winter, like a video played forward and backward.
✔ With microbes living just days, thousands of generations pass in a single year, making this one of the fastest observed natural evolutionary cycles.
✔ 20% of species exhibited long-term genetic shifts, likely driven by environmental changes like the unusually hot, dry summer of 2012, which altered nitrogen metabolism genes.

How Did Scientists Crack This Genetic Puzzle?

Using a supercomputer, researchers reconstructed metagenomes—piecing together DNA fragments like scattered sentences from hundreds of books.

"Each water sample contained shredded genetic 'pages' from countless bacteria," explains microbial ecologist Robin Rohwer. "Our job was to reassemble each species' genome—like sorting sentences back into the right books."

Why Does This Matter for Climate Change?

The study reveals that ecology and evolution are tightly linked, with bacteria constantly adapting to seasonal shifts. But as climate change disrupts weather patterns, scientists wonder:

• Will microbes keep pace with gradual warming and extreme events?

• How will these changes affect carbon storage in lakes and aquatic food chains?

"This research reshapes our understanding of microbial evolution," says marine scientist Brett Baker. "It’s just the beginning of uncovering how tiny organisms drive big ecological processes."

The study was published in Nature Microbiology, offering a glimpse into nature’s intricate dance of adaptation—one season at a time.

https://doi.org/10.1038/s41564-024-01888-3