Abstract
The microbial diversity within cave ecosystems is largely unknown. Ozark caves maintain a year-round stable temperature (12–14 °C), but most parts of the caves experience complete darkness. The lack of sunlight and geological isolation from surface-energy inputs generate nutrient-poor conditions that may limit species diversity in such environments. Although microorganisms play a crucial role in sustaining life on Earth and impacting human health, little is known about their diversity, ecology, and evolution in community structures. We used five Ozark region caves as test sites for exploring bacterial diversity and monitoring long-term biodiversity. Illumina MiSeq sequencing of five cave soil samples and a control sample revealed a total of 49 bacterial phyla, with seven major phyla: Proteobacteria, Acidobacteria, Actinobacteria, Firmicutes, Chloroflexi, Bacteroidetes, and Nitrospirae. Variation in bacterial composition was observed among the five caves studied. Sandtown Cave had the lowest richness and most divergent community composition. 16S rRNA gene-based metagenomic analysis of cave-dwelling microbial communities in the Ozark caves revealed that species abundance and diversity are vast and included ecologically, agriculturally, and economically relevant taxa.
Highlights
Caves, caverns and other karst formations represent unique ecosystems that are relatively unexplored due to their subsurface location
Our results are in agreement with other molecular microbial microbial communities in oligotrophic cave environments are phylogenetically diverse [2,5,10], but studies, showing that microbial communities in oligotrophic cave environments are with a certain degree of stable microbial community structure
Our results add evidence to a growing number of studies that have shown that the microbial diversity in caves goes well beyond samples being brought by water, air, or animals [53]
Summary
Caverns and other karst formations represent unique ecosystems that are relatively unexplored due to their subsurface location. The lack of sunlight precludes photosynthesis except at cave openings where photosynthesis occurs at low levels. Most cave ecosystems are heterotrophic and depend upon organic materials that fall in through cave openings, carried by water, or deposited by cave animals that travel to the surface. Cave biologists focus on the macro-biological communities of caves while ignoring microbial life [4]. The microbial diversity within the soils, streams and ponds in caves is largely unknown. While the lack of sunlight prevents the cavern from being an ideal habitat for most light-dependent macro-organisms, studies have shown that microbial life is diverse, including
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