Lake Mendota in Wisconsin goes through amazing changes with the seasons. In winter, it freezes over, and in summer, it’s often covered in algae. A recent study reveals how these seasonal shifts influence the evolution of the lake’s bacteria.
Researchers from the University of Texas at Austin spent years collecting and analyzing 471 samples of lake microbes. They focused on the genetic changes happening in these tiny organisms over two decades. The findings are fascinating: thousands of bacterial species evolve through the seasons, then often revert back to nearly the same genetic state as the cycle repeats.
Microbes have short life spans, often just a few days, so these genetic changes can happen across thousands of generations in a single year. About 80% of the 2,855 bacterial genomes studied displayed this cyclical evolution, almost like a film playing forwards and then in reverse.
“This study changes how we see microbial communities and their evolution over time,” says marine scientist Brett Baker from the University of Texas at Austin. He believes this is just the start of discovering more about microbial life in nature.
The researchers noticed these microbes respond to environmental changes. Different bacterial strains would rise and fall in dominance depending on the season. Approximately 20% of the species showed more consistent genetic changes spanning many years.
An interesting case occurred in 2012 when the lake faced an unusually hot and dry summer. The bacteria’s nitrogen metabolism genes changed significantly that year, likely due to decreased nitrogen levels from less water flow affecting the lake.
Using a supercomputer, the team analyzed the genetic sequences in water samples, a technique known as metagenomics. This method helps scientists closely examine DNA fragments over time.
Robin Rohwer, a microbial ecologist from the University of Texas, compares the genome of each species to a book, where DNA fragments are like sentences. “To put the books back together, you need to figure out which fragments belong to which book,” he explains.
The study highlights the link between ecology and evolution, suggesting they are connected rather than separate processes. This is vital for researchers, especially in a world facing climate change. Understanding which bacteria will thrive can help predict how lakes absorb carbon and influence aquatic food chains as seasons change.
Climate change is altering seasons, increasing temperatures, and causing extreme weather events. “We don’t know exactly how microbes will react to these changes, but our study indicates they will evolve in response to these gradual and sudden shifts,” Rohwer says.
The research is a significant step in understanding the impact of environmental changes on microbes. It was published in Nature Microbiology.
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Source linkgenetic variations, University of Texas at Austin, ecology and evolution
