Fungal diversity in carbonate caves across diverse substrates

Background/Question/Methods

Kartchner Caverns, located near Benson, Arizona, is a living carbonate cave renowned for its mineralogical and speleothem diversity. Since its discovery in 1974, special attention has been paid toward preserving the cave in pristine condition. As such, Kartchner Cavers has provided a unique opportunity as an established NSF Microbial Observatory to explore microbial communities in subterranean environments. Broadly, this project seeks to define the microbial diversity that exists inside the cave, correlate this diversity with varied cave substrata, and examine how these organisms functionally contribute to cave ecosystems. The focus of the initial portion of the project has been to define the mycological diversity inside the cave through the development of culture-based libraries as a prelude to non-culture based libraries, DGGE community profiling, and metagenomic analysis of select communities to explore functional properties. Preliminary sampling has been conducted across 22 sites throughout the cave system over five substrate types: soil, clay, guano, ancient guano (>40,000 years-old), and mineral surfaces. The substrates were compared by the number of colony forming units (CFU) per sample, the number of morphologically distinct taxonomic units (MTU) recovered, and the number of genera represented

Results/Conclusions

Initial sampling has resulted in the recovery of 273 isolates representing 125 MTU’s and 29 genera. In comparing CFU’s, the mineral and guano samples had the lowest and highest recovered CFU’s, respectively, and values were far outside the range of the other substrates and were not included in statistical analyses. Comparing recovery from the other substrates, there were significantly higher CFU’s in soil than clay or ancient guano. There was no significant difference between the number of genera found across all five substrates. However, the clay and mineral surfaces had significantly fewer MTU’s than the other substrates. These preliminary results suggest that clay and mineral surfaces support smaller and less diverse communities of micro fungi than other substrates examined in the cave, presumably due to reduced carbon content and other nutrients. Preliminary data also revealed differences in the taxonomic diversity between the two distinct sections of the caverns: one section that harbors a bat population, which had less MTU diversity, and the other section that has not harbored bats for many millennia, which had greater MTU diversity. Currently, DGGE profiles are being generated from recovered total community DNA and compared to help further characterize these communities.