CAREER: Unearthing impacts of leguminous plant co-occurrence on genetic diversity of bacterial mutualists

In nature, organisms often work together in mutually beneficial ways. However, while theory predicts these beneficial relationships reduce variation in both partners, real-world evidence often contradicts this, especially for bacteria that can thrive with or without plant hosts. This project investigates whether plant host presence over time and space helps maintain bacterial variation. The focus is on an ecologically, agriculturally, and economically important interaction between leguminous plants and their mutualistic bacteria, which convert atmospheric nitrogen into a usable form inside structures on plant roots called nodules. This proposal will benefit agricultural production and ecological conservation, prepare the future scientific and agricultural workforce, and connect students at multiple educational levels with ecological and evolutionary concepts, as well as artificial intelligence-enabled image, statistical, and modeling analysis tools. The nitrogen-fixing symbiosis studied here is one of the most ecologically, agriculturally, and economically important plant-bacteria symbioses. Understanding the host drivers of bacterial variation will inform better decision-making in agriculture and restoration projects, boosting the effectiveness of nitrogen-fixing bacteria, which are crucial for eco-friendly farming. Educational programs will develop curricula that foster project-based learning in Pennsylvania high schools through a “Community Symbiosis Curriculum” aligned with new science standards and in undergraduate plant science courses with plant distribution models to build quantitative and computational skills. This initiative supports workforce development by offering hands-on training with educational experts and creating near-peer mentors for high school students, inspiring more young people to pursue careers in agriculture and biotechnology. In nature, organisms interact in complex ways. This project examines mutualism, where both organisms benefit, a relationship that poses a paradox: evolutionary theory suggests mutualisms should reduce genetic diversity, yet empirical data often contradict this, especially for bacterial mutualists that can live with or without hosts. This CAREER project study tests the hypothesis that has received little attention: that variation in host presence and identity explains this diversity. The project has four main goals that leverage both traditional and artificial intelligence-enabled analysis of data from field sampling, greenhouse experiments, and computer-based simulations. First, identify patterns by analyzing characteristics of different plants to understand which ones support which bacteria. Second, conduct multigenerational experiments to determine whether cohabitation with certain hosts promotes bacterial diversity. Third, simulate evolution using AI models to explore how relationships with plants affect bacterial diversity over time. Fourth, collect field samples from legume plants and engage high school and college students in research activities, including an annual outreach event to promote agricultural education. This project focuses on a plant-microbe mutualism with significant implications for food production and nutrient cycling (biological nitrogen fixation). It identifies host traits that maintain mutualist diversity and employs machine learning to link ecological and evolutionary processes in bacteria—an approach rarely applied at these scales. By integrating research and teaching, the project offers unique insights into the evolution of bacterial mutualists, with practical benefits for engineering beneficial plant-microbe interactions. It also creates opportunities for scientists and students to explore ecology, evolution, biotechnology, and artificial intelligence through visible plant-microbe interactions. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broa NSF Award ID: 2541790 | Program: 01003031DB NSF RESEARCH & RELATED ACTIVIT,01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Liana Burghardt | Institution: Pennsylvania State Univ University Park, UNIVERSITY PARK, PA | Award Amount: $1,352,109 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2541790 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2541790.html