Evolution and Mechanisms of Thermotolerance in Cyanobacteria

University Of Chicago, Chicago IL

Investigators

Abstract

Phytoplankton are tiny organisms that form the base of food webs in lakes, rivers, and oceans, and sometimes cause harmful algal blooms. Understanding how phytoplankton respond to changing temperatures is crucial, but we currently lack the knowledge to predict their future state. Our project investigates a type of phytoplankton called cyanobacteria that thrive in hot springs. We will analyze their genetic adaptations and responses to temperature changes, both over short timescales and across long-term laboratory evolution. This will help us uncover how they survive extreme heat. We will then test how well our findings apply to cyanobacteria in freshwater sources across the U.S. This research will help predict which phytoplankton are most vulnerable to warming and explore ways to engineer heat-resilient cyanobacteria that produce supplements, biofuels, and other valuable products. We will also create educational programs to train future scientists in cutting-edge biological data analysis and engage the public in how microbiology can inform our understanding of life on earth. Phytoplankton responses to warming are mechanistically poorly understood, limiting our ability to predict their future fitness, forecast harmful algal blooms, or cultivate them effectively for bioproducts. This project aims to elucidate thermal adaptation mechanisms in cyanobacteria by integrating heat stress responses with eco-evolutionary processes. We will leverage thermophilic cyanobacteria that evolved across natural temperature gradients approaching the upper thermal limit for oxygenic photosynthesis, likely leaving strong genomic signatures of thermal adaptation. First, we will identify genomic features—including amino acid frequencies and gene content—that predict optimal growth temperature (OGT) in cyanobacteria. We will then test these models in mesophilic cyanobacteria and metagenomic data from freshwater samples, including NSF’s NEON data, to identify thermally maladapted species. Second, we will distinguish adaptive from maladaptive heat stress responses. This involves analyzing transcriptomic and metabolomic responses of isolates with varying heat-stress survival, using sparse canonical correlation analysis to link gene expression patterns with metabolite profiles and thermal tolerance. Third, we will investigate the role of horizontal gene transfer (HGT) in rapid thermotolerance evolution through laboratory selection experiments introducing thermotolerant donor DNA to maladapted strains and comparing these findings to the contribution of HGT in natural populations. This research will generate novel, testable insights into cyanobacterial thermal adaptation, providing frameworks for predicting phytoplankton traits from genomes, engineering thermotolerance in industrial strains, and utilizing HGT-facilitated artificial evolution. Furthermore, we will develop workshops to train students in advanced biological data analyses and engage in outreach to inform the public about the importance of algae and cyanobacteria. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.