Microbiology of the stalactites from Grotta dei

Grotta dei Cervi is a cave which opens into the Oligocenic Calcarenites at 26 m above sea level on the channel of Otranto, 370 m NE of Porto Badisco, Lecce, southeastern Italy. It was discovered on February 1, 1970. From the geomorphological point of view, the cave is the site of an ancient underground water table. The innumerable concavities which are visible on the roof of the gallery have formed by the effect of the whirling and turbulence of water. The cave consists of a main gallery running NE-SW, from which three cavities branch off running prevalently SW-NE. The total planimetric extent is about 1550 m (the central branch alone runs for 320 m from the entrance). The eastern gallery reaches a depth of 26–28 m below ground in its final stretch. From the western gallery there is an entry to a series of galleries and passages. The central gallery, which reaches sea level at its maximum depth, is blocked, especially at the end, by a major slide and tends towards the surface above. Even the roof of the gallery reaches 15.3 m below ground level. The central gallery contains rock art paintings in red ochre showing stylized, partly faded, figures of men and animals. Black paintings, made with guano, represent cruciform and other geometric figures and sorceries which are difficult to interpret. Because of the wealth of the rock art paintings, the cave was defined by Graziosi [5] as “the shrine of Prehistory” after verifying “the sacred character, in that religious, or rather, magic-religious ceremonies were performed”. The knowledge of microbial communities in caves is scant [6]. Contradictory data can be found in the literature, e.g. that chemolithoautotrophic bacteria are likely to be primary producers in caves [14], or that they play an insignificant role in the cave ecosystem [3]. Microbial communities of caves usually rely on allochthonous input of organic matter which is transported from the surface by water. Dissolved organic carbon content in dripping waters from some caves is highly variable, ranging from < 5 mg C/liter to 2200 mg C/liter [10]. The biodeteriorative role of microbial communities, especially those of actinomycetes growing on hypogean environments which contain rock art or mural paintings, has been emphasized by some authors [6, 7, 11]. We investigated heterotrophic microbial communities from active stalactites from Grotta dei Cervi, Porto Badisco, Italy. This study was of particular interest because the difficult, restricted access to the cave preserves it from external contamination.