Carbonatogenic Bacteria in the Maros-Pangkep Karst: Protectors or Threat to Prehistoric Paintings?

Abstract

The Maros-Pangkep karst region hosts prehistoric cave paintings recognized by UNESCO as a world cultural heritage site. The presence of calcium carbonate (CaCO₃) on the surface of these artworks suggests the involvement of carbonatogenic bacteria, which facilitate CaCO₃ production or deposition. While these bacteria have been explored for their potential in stone artwork conservation, their role in either preserving or obscuring prehistoric paintings remains unclear. This study aims to identify carbonatogenic bacteria associated with the Maros-Pangkep cave paintings and evaluate their CaCO₃ precipitation potential. Bacteria were isolated using Calcium Carbonate Precipitation (CCP) medium, and their CaCO₃ precipitation capacity was assessed by measuring precipitate mass and ammonia (NH₃) levels. Molecular identification was conducted using 16S rRNA gene sequencing. Eighteen bacterial isolates were obtained from swab samples collected in Parewe and Bulu Sipong caves, ten of which were identified as carbonatogenic. Among these, two isolates exhibited the highest CaCO₃ precipitation: Ps1-d produced 2.45 ± 0.07 mg/ml CaCO₃ with 946.3 ± 26.3 mg/l NH₃, while Ps8-b produced 1.80 ± 0.05 mg/ml CaCO₃ with 763.4 ± 21.2 mg/l NH₃. Molecular analysis identified Ps1-d as Bacillus cereus strain bk and Ps8-b as Bacillus sp. NCCP-428. These findings have significant implications for both (1) the potential application of carbonatogenic bacteria in the conservation and restoration of stone artworks and (2) the development of strategies to inhibit excessive CaCO₃ deposition to prevent the obscuration of cultural heritage paintings.