Dissertation Research: Disentangling a Potential Tri-Kingdom Mutualism in the Guiana Shield

Purdue University, West Lafayette IN

Investigators

Abstract

Very different types of organisms can interact in ways that allow them to survive together when they would be unable to survive alone. These interactions can have major impacts on entire ecosystems. This project will test whether termites, bacteria, and a fungus depend on each other in a tropical rainforest. Scientists hypothesize that wood-feeding termites disperse the reproductive structures of a wood-decaying fungus so it can colonize new substrates, that the fungus houses bacteria beneficial to termites, and that the bacteria receive shelter inside the fungus. Because this three-way interaction is built on wood-feeding organisms, results of the study will augment knowledge of how decomposition, or nutrient recycling, occurs in tropical ecosystems. Additionally, this project underscores how much remains to be learned about species interactions, especially in biodiverse ecosystems. This study will investigate a potential tri-kingdom mutualism in the Guiana Shield. Field observations have led to the hypothesis that a wood-decay fungus, Guyanagaster necrorhiza, uses wood-feeding termites as its dispersal agent. Benefits to the termites for consuming G. necrorhiza remain elusive. Recently, it was discovered G. necrorhiza fruiting bodies harbor a community of Enterobacteriaceae, which are frequently identified as important nitrogen-fixing mutualists. This project will test the hypothesis that G. necrorhiza recruits these bacteria from its local environment as part of its dispersal strategy. State-of-the-art genetic sequencing technology will be used to characterize the bacterial communities in G. necrorhiza and substrates of the local environment to determine if and from where G. necrorhiza is recruiting bacteria. If G. necorhiza is recruiting specific bacteria, it is hypothesized that these bacteria fix nitrogen, making the fruiting bodies a rich source of nitrogen for termites. A series of chemical tests will be performed to determine if G. necrorhiza fruiting bodies are nitrogen-enriched, and if this enrichment is due to nitrogen-fixing bacteria that they harbor. If both hypotheses are supported, the conclusion will be that nitrogen-starved organisms, such as wood-feeding termites, feed on G. necrorhiza to supplement their diet and that they subsequently disperse the spores. By using wood-feeding termites as dispersal agents, G. necrorhiza accomplishes spore dispersal targeted to its desired substrate, wood.