Colonization of Roman tombs by calcifying cyanobacteria

Calcifying cyanobacteria have colonized the tombs of the Necropolis of Carmona (Seville, SW Spain). Scytonema julianum (Frank) Richter was the main colonizer of the cavities and was able to thrive in most tombs, though the tombs differed considerably in architecture and exposure. Scytonema julianum grew on all surfaces not directly exposed to air currents or long periods of sunlight. The distribution of Geitleria calcarea Friedmann was more restricted; it was found in only one tomb, where it coated nearly all of the wall surfaces at the dim end of the lighted zone. Calcification of the sheaths of these two organisms differed in the pattern and location of crystallization. Calcification of Scytonema julianum persisted in culture even under changing conditions. Confocal scanning laser microscopy allowed separate observation of cellular and sheath structures.