Biology Department Chair, Professor of Biology Portland State University, United States
Abstract: Mushroom-forming fungi are hosts to bacterial communities both within their hyphospheres and within their fruitbody tissues. Compared to the microbiomes of plant and animal hosts, very little is currently known about those of fungi, including how they vary among hosts as well as how they influence the health of their hosts. Mushroom-forming fungi fulfill key roles within terrestrial ecosystems (e.g., as mycorrhizal partners in forests, or as decomposers of woody materials) and some are of economic importance as food crops, and thus understanding their relationships with their microbiomes will likely prove useful in understanding how their ecological and economic functions may be affected under increasing anthropogenic impact.
In order to assess the effect of mushroom taxonomy and lifestyle on microbiome composition we sampled hyphosphere soil and fruitbody tissue from ca. 200 mushrooms spanning eight taxonomic orders within Agaricomycotina and three separate lifestyles (mycorrhizal, saprobic, and parasitic). Bacterial communities were characterized via 16S metabarcoding using MiSeq sequencing. Bacterial communities were compared between the hyphosphere and tissue, as well as amongst taxonomic orders and lifestyles using PERMANOVA to test for overall differences in community composition, and the ANCOMBC R package to test for differentially abundant taxa. In ongoing work, PICRUSt will be used to predict gene content from 16S data, and similar comparisons will be made based on predicted functional profiles.
A total of 883 quality-filtered amplicon sequence variants (ASVs) were recovered. Of these, about 1/3 were present only in the hyphosphere, 1/3 present only in fruitbody tissue, and 1/3 present in both. Hyphosphere and tissue communities differed significantly from one another, and both hyphosphere and tissue communities differed significantly among host orders. We hypothesize that these differences will be found to be driven by a subset of ASVs with differing abundances between the hyphosphere and the fruitbody, and potentially with differing abundances among host orders. Additionally, we expect ongoing analyses to reveal differences in communities between host lifestyles.
Our results indicate that bacterial communities associated with fungal fruitbodies are not simply subsets of those associated with the larger organism within the hyphosphere. The taxonomy of the host is predictive of community composition both within the hyphosphere and within fruitbody tissue, and the same is predicted to be true of host lifestyle. The present study examines a large taxonomic and ecological breadth of hosts, offering new insights into the diversity and potential function of fungal microbiomes.
