Collaborative Research: EXPAND: Role of Melanin in the Interactions between a Polyextremotolerant Fungus and its Photoautotrophic Partners

Melanin is a pigment that protects organisms from ultraviolet (UV) radiation and environmental stresses. Polyextremotolerant fungi found in cold deserts, naturally produce melanin, incorporating it into their cell wall and releasing it under certain conditions. In nutrient-poor environments, where organic material is scarce, these fungi may form symbiotic partnerships with photosynthetic organisms like algae and cyanobacteria. Within these partnerships melanin may be exchanged for essential nutrients. Therefore, melanin could be available to help protect partners from UV radiation, cold temperatures, and water scarcity, enabling the survival of biological soil crusts. However, the genetic or metabolic triggers for melanin excretion are not well understood. This project investigates the symbiosis between a polyextremotolerant fungus and its photosynthetic partners, aiming to uncover the triggers regulating melanin production. It also develops predictive models of the metabolic interactions of the entire microbial community and validates these findings using genetic tools. Additionally, the fungus could serve as a valuable resource for large-scale melanin production, with applications in UV-protective products and advanced materials for the aerospace and other industries. Beyond scientific discovery, the project enhances the STEM workforce by implementing educational, outreach and mentoring activities. This project aims to address two key deficiencies in understanding the role of a melanized fungus (Exophiala viscosa) in biological soil crusts: the mechanisms regulating melanin production and excretion, and the lack of experimental evidence for metabolite exchange between the melanized fungus and photosynthetic microbes. To tackle these knowledge deficiencies, the proposed research: 1) utilizes ‘omics’ data to discern the molecular mechanisms regulating melanin production in the fungus, when tri-cultured with an algae and a cyanobacterium; 2) develops and refines microbial community metabolic models to explore inter-species metabolic interactions and assess how carbon and nitrogen sources from the algae and cyanobacterium impact melanin production; and 3) employs genetic tools developed for the melanized fungus to investigate the interactions driving melanin secretion, applying targeted gene editing informed by the modeling framework. Aided by mathematical modeling and experimental validation, this directed experimental design investigates specific one-on-one interactions among “keystone” microbial species to understand the community dynamics and foster symbioses critical for community survival. This approach promises a deeper understanding of microbial interactions, which differs from typical microbial ecology metagenomics-focused studies that do not provide detailed molecular insights into microbial interactions. 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.