Abstract
Caves are nutrient-limited and dark subterranean ecosystems. To date, attention has been focused on geological research of caves in China, whilst indigenous microbial diversity has been insufficiently characterized. Here, we report the fungal diversity in the pristine, oligotrophic, karst Heshang Cave, central China, using a culture-dependent method coupled with the analysis of the fungal rRNA-ITS gene sequences. A total of 194 isolates were obtained with six different media from 14 sampling sites of sediments, weathered rocks, and bat guanos. Phylogenetic analysis clustered the 194 sequenced isolates into 33 genera within 15 orders of three phyla, Ascomycota, Basidiomycota, and Zygomycota, indicating a high degree of fungal diversity in the Heshang Cave. Notably, 16 out of the 36 fungal genera were also frequently observed in solution caves around the world and 23 genera were previously found in carbonate cave, indicating potential similarities among fungal communities in cave ecosystems. However, 10 genera in this study were not reported previously in any solution caves, thus expanding our knowledge about fungal diversity in cave ecosystems. Moreover, culturable fungal diversity varied from one habitat to another within the cave, being the highest in sediments, followed by weathered rocks and bat guanos as indicated by α-diversity indexes. At the genus level, Penicillium accounted for 40, 54, and 52% in three habitats of sediments, weathered rocks, and bat guanos, respectively. Trichoderma, Paecilomyces, and Aspergillus accounted for 9, 22, and 37% in the above habitats, correspondingly. Despite of the dominance of Penicillium in all samples, β-diversity index indicated significant differences between each two fungal communities in the three habitats in view of both the composition and abundance. Our study is the first report on fungal communities in a natural pristine solution cave system in central China and sheds light on fungal diversity and functions in cave ecosystems.
Highlights
Fungi are eukaryotic and organotrophic microorganisms, comprising at least 1.5 million species (Hawksworth, 2001), most of which are uncharacterized despite their significant roles in nature
Most of the isolates were recovered with Martin agar (MA) (47, 24%), Czapek agar (CZA) (44, 23%), Potato dextrose agar (PDA) (43, 22%), and Sabouraud agar (SDA) (39, 20%) media, indicating the applicability of these media in isolating cave fungi
colony forming units (CFUs) counts on PDA in the three habitats were the highest in sediments followed by bat guanos and weathered rocks with a value of (3.6 ± 0.001) × 103 CFU.g−1, (9.81 ± 0.07) × 102 CFU.g−1, and (1.79 ± 0.03) × 102 CFU.g−1, respectively
Summary
Fungi are eukaryotic and organotrophic microorganisms, comprising at least 1.5 million species (Hawksworth, 2001), most of which are uncharacterized despite their significant roles in nature. High indigenous microbial diversity, unique metabolic features, and ecological functions within the domains of bacteria, archaea, and fungal groups have been observed in caves via both culture-dependent and culture-independent methods (Høeg, 1946; Caumartin, 1963; Bastian et al, 2010; Wang et al, 2010b; Vanderwolf et al, 2013; Pusz et al, 2015). The interactions between these subterranean microbes and caves have been elucidated (Groth et al, 1999; Engel et al, 2001; Spear et al, 2007; Onac and Forti, 2011). It has been shown that both the number and community composition of airborne fungi are strongly correlated with numbers of cave visitors (Wang et al, 2010b) and activities of arthropods (Bastian et al, 2010; Shapiro and Pringle, 2010; Porca et al, 2011; Ogórek et al, 2013; Griffin et al, 2014)
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