The Microbial Diversity of Caves

Abstract

Oligotrophic caves represent an important environment for studying microbial community adaptation, where diversity is likely driven by available energy and nutrient sources, from the heterotrophic breakdown of scant allochthonous organic carbon delivered by vadose-zone groundwater to autotrophic growth using in situ redox-active compounds. While historically cave microbiology was based on cultivation approaches, the inherent bias of such techniques provided an incomplete view of cave diversity. Modern molecular techniques demonstrate that microbial populations in caves are remarkably diverse and demonstrate both community and organismal adaptations to the resource limitation of the subsurface. While most studies in caves have focused on the role and diversity of bacterial populations, the fungi and archaea also appear to play important roles in community structure and energetics, albeit at polar ends of the nutrient spectrum. Together these data suggest that current cave microbiology research is starting to reveal the potential for a cave microbiome that represents the core of microbial diversity in caves.