Shotgun metagenomics of Sterkfontein Karst groundwater and weathered rock (ghost-rock)

Karst systems represent an important carbon and freshwater reservoirs. Although karst systems have been studied for many years, a new paradigm has emerged that suggests some of them could be formed by ghost rock processes. Contrarily to the classical total karstification, ghost rock karstification leaves in place a weathered rock, called the ghost rock, that can constitute a microbial habitat. The activity of microorganisms in this newly described compartment may affect the entire karst biogeochemical processes.The first results of a geomicrobiological study of the Sterkfontein cave system in South Africa show that these ghost rocks are mainly composed of iron and manganese oxides mixed with organic matter of putative microbial origin. To further understand the microbial community inhabiting these ghost rocks, its specificity compared to groundwater, and its functional impact on the karst system of Sterkfontein, a metagenomic analysis from both ghost rocks and groundwater samples was performed.