Bacterial calcification in limestone caves

Bacteria were isolated from cave deposits and sub‐cultured using several media containing calcium salts. Calcification began shortly after inoculation, the results being broadly similar in all media. Calcite spheres or hemispheres with a radiating fibrous structure were produced by impregnation of bacterial capsules. Colonies developed shells of calcite due to the impregnated capsules. The study of the cave deposits themselves revealed calcite structures very similar to the capsule impregnations found in the laboratory cultures. From this it would appear that bacteria become calcified in vivo in some limestone caves.