Comparing Fungal Secretions to Uncover Carbon Compound Degradation Pathways

Fungal secretions
Pyrenochaeta sp. DS3sAY3a growing in liquid culture. As the fungus grows, brown-colored manganese oxides are formed. Here, the oxides can be seen associated with biomass and suspended in solution. (Carolyn Zeiner)

Their unassuming appearances may cause them to be overshadowed by the plants or animals in their natural habitats, but fungi play key roles in maintaining their ecosystems. From breaking down leaf litter and decaying wood in forests to cleaning contaminated soils and waters, fungal enzymes are being characterized for potential use in a wide variety of energy and environmental challenges.

Fungal secretomes, those collections of all molecules secreted by a cell, contain enzymes that can break down plant cell wall components such as cellulose, hemicellulose and lignin. These capabilities make them of interest to bioenergy researchers looking for cost-effective ways to convert plant mass into sustainable, alternative transportation fuels. In a study published online July 19, 2016 inPlos ONE, a team led by researchers at Harvard University and Woods Hole Oceanographic Institution (WHOI) conducted a comparative analysis of the secretomes of four recently-isolated and sequenced filamentous Ascomycete fungi to learn more about the variety of pathways they deploy to break down carbon compounds.

“While the secretomes of model organisms such as the white-rot Basidiomycete Phanerochaete chrysosporium and members of the Aspergillus genus have been well characterized, little is known about the enzymatic capabilities of environmental isolates. Thus, the mechanisms of carbon degradation by many ubiquitous soil fungi remain poorly understood,” said study first author Carolyn Zeiner, now a postdoctoral research associate at Boston University. “This work suggests that a more taxonomically and mechanistically diverse community of fungal species contributes to environmental lignocellulose degradation beyond the traditional wood-rot Basidiomycetes.”