Northeastern forests are becoming warmer (W), which brings reduced winter snowpack and increased soil freeze thaw cycle events (FTC). W+FTC can change soil temperature, redox status, and nutrient availability, with consequences on microbial populations that drive ecosystem functioning. Microbes can undergo evolutionary adaptation to environmental changes on short timescales, with unknown effects on microbial mediated nutrient cycling. We hypothesized that metal cycling and denitrifying genes are under selection from W+FTC. We utilized a long-term experimental climate change experiment to grow anaerobic microbial enrichment consortias, and then recovered hundreds of high and medium quality metagenome-assembled-genomes (MAGs). We identified non-neutrally evolving genes in MAG populations using the population genetics test Tajima D. Our preliminary analysis revealed genes important for anaerobic nutrient cycling were impacted by W+FTC and that genes exhibited non-random evolutionary patterns. This suggests W+FTC induces balancing selection and positive selection. Future work will investigate molecular signatures of microbial evolution to W + FTC in MAGs and bacterial isolates using interspecies and intraspecies selection proxies such as Tajima D and the ratios between nonsynonymous and synonymous mutations.

‍