The Pillars of the Earth

This is a scanning electron microscopy image1 of enigmatic microbial features associated with carbonate minerals from a limestone cave in Spain (Ardales Cave, Malaga). This unusual microorganism resembles beads on a string forming bridges between mineral grains.
Caves are subterranean environments where the precipitation of secondary minerals and microbial growth are enhanced. These subterranean environments might be considered extreme for life, in which highly specialized microorganisms are able to interact with minerals and promote biomineralization. Several geomicrobiological studies have revealed the presence of enigmatic microbial features associated with cave speleothems which are not related to any known microorganism.
The Pillars of the Earth is a historical novel by Ken Follett. Bacteria are pillars of the Earth (Lowe, D. R., 1980. Stromatolites 3,400 Myr old from the Archean of Western Australia. Nature, 284, 441-443).
1This image was performed using a Jeol JSM-7001F field emission scanning electron microscope at Instituto Superior Técnico (University of Lisbon, Portugal), with secondary X-rays mode and an acceleration voltage of 15 kV, on a sample previously sputter coated with a thin gold/palladium film.