Lake Mendota in Wisconsin changes with the seasons. In winter, it freezes over, and in summer, it blooms with algae. A recent study reveals how these seasonal shifts affect the lake’s bacteria.
Researchers from the University of Texas at Austin conducted a major study over 20 years, analyzing 471 samples of microbes. They focused on how bacteria changed genetically over time. The results were surprising: many bacteria evolved rapidly from one generation to the next, only to return to their earlier forms as the seasons changed. This rapid evolution means that in just one year, these tiny organisms can go through thousands of generations!
The researchers found that 80% of the 2,855 bacterial genomes they studied showed this cyclical evolution. It’s like watching a video play forward and then rewind back to the start. This discovery changes our understanding of how microbial communities develop over time, according to marine scientist Brett Baker from the University of Texas at Austin.
As seasons shift, different strains of bacteria thrive while others fade. About 20% of the species examined showed ongoing genetic changes over several decades. For instance, during the unusually hot and dry summer of 2012, a noticeable change happened in the bacteria’s nitrogen metabolism. With less water flowing into the lake, there were fewer nitrogen-producing algae, which likely influenced the bacteria’s ability to adapt.
Using a supercomputer, researchers created metagenomes from each water sample. This advanced method allows scientists to look closely at genetic sequences from DNA fragments over time.
Imagine each species’ genome as a book and each DNA fragment as a sentence. The team had to identify which sentences belonged to which books and piece them back together.
The outcomes of this study emphasize how ecology and evolution work together. This understanding is crucial for researchers, especially as our planet faces climate change. Knowing which bacteria will thrive helps scientists predict how lakes might absorb carbon and how aquatic food chains will adapt to warmer weather.
Climate change is altering seasons and bringing more extreme weather. While we don’t know exactly how microbes will react to these changes, the study indicates they will continue to evolve in response to both gradual shifts and sudden changes.
The full research is published in Nature Microbiology.
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