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

当不同种类的生物无法单独生存时，它们可以相互作用，使它们能够共同生存。这些相互作用会对整个生态系统产生重大影响。这个项目将测试白蚁、细菌和真菌是否在热带雨林中相互依赖。科学家们假设，食木白蚁分散了一种腐木真菌的生殖结构，这样它就可以在新的基质上定居，真菌容纳了对白蚁有益的细菌，而细菌在真菌中得到了庇护。由于这种三方互动是建立在以木材为食的生物基础上的，因此研究结果将增加对热带生态系统中如何发生分解或营养循环的认识。此外，该项目强调了物种之间的相互作用，特别是在生物多样性生态系统中，还有多少有待了解。本研究将探讨圭亚那地盾中潜在的三国共生关系。实地观察得出了一种假设，即一种木材腐烂真菌，Guyanagaster necrorhiza，使用食木白蚁作为它的扩散剂。白蚁食用白蚁的益处仍然难以捉摸。最近，人们发现G. necrorhiza子实体中含有一个肠杆菌科菌群，肠杆菌常被认为是重要的固氮共生菌。该项目将验证一种假设，即死亡弧菌从当地环境中招募这些细菌，作为其传播策略的一部分。最先进的基因测序技术将被用于描述死亡弧菌中的细菌群落和当地环境的底物，以确定死亡弧菌是否以及从哪里招募细菌。如果G. necorhiza正在招募特定的细菌，假设这些细菌固定氮，使子实体成为白蚁丰富的氮来源。将进行一系列化学试验，以确定G. necrorhiza子实体是否富含氮，以及这种富集是否由于它们所含的固氮细菌。如果这两种假设都得到支持，那么结论将是缺氮的生物，如食木白蚁，以G. necrorhiza为食来补充它们的饮食，并随后传播孢子。通过使用以木材为食的白蚁作为扩散剂，G. necrorhiza完成了针对其所需基质木材的孢子扩散。

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.