PS 31-117 - The air mycobiome is decoupled from the soil mycobiome in the California San Joaquin Valley

Background/Question/Methods

Dispersal of airborne and dust-borne spores is central to the assembly and structure of most fungal communities. The majority of fungal pathogens are usually dispersed through the air, which allows establishment in plant or animal hosts at great distances. Understanding the dynamics of fungal spore dispersal in air can aid in preventing or mitigating harmful fungal diseases. Here, we make use of metabarcoding of the internal transcribed spacer region of fungal rDNA to characterize the fungal community in over one thousand samples of soil and settled dust in the San Joaquin Valley of California, the most productive agricultural region in the United States and home to a rapidly growing population of 4.2 million people. We ask the questions: What are the similarities and differences in the assemblages of airborne fungi and the communities of fungi in soils in the San Joaquin Valley? How do these patterns change over space and time? What can we infer about the possible origins of fungal pathogens of humans and plants in the San Joaquin Valley and how does this influence our understanding of the interface between substrates where fungi grow and the air and dust medium by which fungi disperse?

Results/Conclusions

We show that the assemblages of fungi in settled dust are more similar to one another, even when sampled from as far away as 160km, than to the fungal communities in nearby soils. This result is surprising because settled dust sampling was done just above the soil surface, and our expectation was that sampled airborne fungi would reflect the nearby soil fungal community. Our findings indicate that the air and airborne dust medium in the San Joaquin Valley can work to homogenize airborne and dust-borne fungi as low as 50cm above the soil surface. Further, we show that the soil fungal community is distinct from the assemblage of airborne and dust-borne fungi. We hypothesize that persons who spend considerable time outdoors on land whose soil contains few detectable pathogens could still be exposed to airborne fungal spores from elsewhere. The air in the San Joaquin valley is the dispersal medium for multiple fungal species, including the pathogenic fungus that causes Valley fever, Coccidioides, and myriad wild plant and crop pathogens. Our findings may contribute to a better understanding of fungal disease and help to prevent the spread of fungal pathogens of both humans and plants.