Abstract
We investigated the effect of varying storage time and storage temperature on fungal species’ isolation as part of a case study of Illinois cave sediment samples. A deeper understanding of cave fungal communities may influence eco-epidemiology studies of emerging or re-emerging cave fungal pathogens. Using culture-dependent techniques, we isolated geophilic fungi from homogeneous cave sediment samples from three Illinois caves. Each sample was stored under five different temperatures ranging from −80 °C to 22 °C. Cave sediment was periodically removed at five different time periods from 48 h to 1 year, serially diluted with distilled water, lawn plated onto two different media, and monitored for fungal colonies. We isolated colonies and confirmed identity through nrDNA sequence similarity. Our results suggest that storage time was more important than storage temperature for the isolation of a wide diversity of geophilic fungal taxa. Importantly, our results show that varying storage conditions will alter both the kind of taxa and abundance of those taxa, suggesting that comparative studies of fungal diversity across studies should employ similar storage conditions. Lastly, future investigations should utilize multiple genetic markers because the fungal barcode region lacked species-level resolution for many isolates within common Illinois geophilic fungal genera.
Highlights
Understanding microbial community composition using culturebased isolation techniques remains foundational for fungal research requiring phenotypic and physiological information for a multitude of basic biological questions as well as biomedical and industrial applications [1]
Identified genera/group isolated over the entire storage time and storage temperatures were Apiotrichum/Trichosporoni group, Cladosporium, Debaryomyces, Epicoccum, Mortierella, Myriodontium, Oidiodendron, Penicillium, and Pseudogymnoascus/Geomyces group (Table 1)
The results of this study support our hypothesis that altering both the sample storage time and storage temperature effectively increased the overall diversity of cave fungal genera isolated from cave sediment samples (Table 1); only storage time was statistically significant for the overall community
Summary
Understanding microbial (fungi and bacteria) community composition using culturebased isolation techniques remains foundational for fungal research requiring phenotypic and physiological information for a multitude of basic biological questions as well as biomedical and industrial applications [1]. Current culture-dependent isolation techniques use a range of media that support the growth of a wide range of fungi. Inhibitory compounds can be added to suppress the growth of fast-growing fungi [6] or bacteria [8]. One alternative to changing the culture medium or using inhibitory compounds is to vary the incubation temperature. This approach underscores that fungal growth and spore germination temperature requirements vary between individual fungal species. Some fungal spores require heat or cold treatment to activate germination [10]
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