In a study published in Nature Microbiology, researchers discovered that bacterial species in Lake Mendota, Wisconsin, undergo rapid evolution over the course of a year in response to changing seasons. Despite these changes, most species return to genetic states similar to those prior to evolutionary pressures. The researchers, led by Robin Rohwer, found hundreds of bacterial species undergoing this type of change, revealing a unique pattern of evolution that repeats each year, resembling a movie played on a loop.
The team utilized a collection of 471 water samples taken over 20 years from Lake Mendota to analyze changes in bacterial genomes. By assembling metagenomes from DNA fragments left behind by bacteria, they created a record of genetic sequences over time, resulting in the longest metagenome time series ever collected. This archive provided insights into how microbial communities evolve over time, shedding light on microbial ecology and evolution in natural systems.
In 2012, Lake Mendota experienced unusual conditions, including early ice melt, hot and dry summer weather, reduced water flow, and scarce algae. Many bacteria in the lake underwent significant gene shifts related to nitrogen metabolism, likely in response to these environmental changes. The study found that 1 in 5 bacterial species had major gene changes that played out over years, indicating that microbes can adapt to both gradual and abrupt changes caused by climate change.
Unlike laboratory experiments, Rohwer and Baker’s study involved analyzing bacterial evolution in complex and ever-changing conditions in nature. By using supercomputing resources to reconstruct bacterial genomes from DNA sequences, the researchers were able to analyze over 30,000 genomes from 2,800 different species. This enabled them to understand how bacteria respond to various environmental conditions and how they evolve over time in a natural setting.
The study provides valuable insights into how bacterial communities in Lake Mendota adapt to changing seasons and environmental conditions. It also offers a glimpse into how these microbes may respond to climate change, particularly in the face of extreme weather events predicted for the midwestern U.S. in the coming years. Understanding microbial evolution in natural systems like Lake Mendota can help scientists predict how these organisms may evolve in response to environmental changes.
The research was supported by various organizations, including the U.S. National Science Foundation, U.S. National Institutes of Health, U.S. Department of Energy, and the Simons Foundation. The study highlights the importance of studying microbial evolution in natural settings to gain a better understanding of how these organisms respond to changing environments. Through continued research, scientists hope to unravel the complexities of bacterial evolution and its implications for ecosystem dynamics and climate change adaptation.