Halophilic bacteria are colonizing the exhibition areas of the Capuchin Catacombs in Palermo, Italy

Abstract

The Capuchin Catacombs of Palermo, Italy, contain over 1800 mummies dating from the 16th to 20th centuries AD. Their environment is not conducive to the conservation of the remains due to, among other factors, water infiltration, which is producing salt efflorescences on the walls. A multiphasic approach was applied to investigate the halophilic microbiota present in the Catacombs. Enrichment cultures were conducted on media containing different NaCl concentrations, ranging from 3 to 20 %. For screening of the strains, the following two PCR-based methods were used and compared: fluorescence internal transcribed spacer PCR (f-ITS) and random amplification of polymorphic DNA (RAPD) analyses. Results derived from RAPD profiles were shown to be slightly more discriminative than those derived from f-ITS. In addition, the proteolytic and cellulolytic abilities were screened through the use of plate assays, gelatin agar and Ostazin Brilliant Red H-3B (OBR-HEC), respectively. Many of the strains isolated from the wall samples displayed proteolytic activities, such as all strains belonging to the genera Bacillus, Virgibacillus and Arthrobacter, as well as some strains related to the genera Oceanobacillus, Halobacillus and Idiomarina. In addition, many of the strains isolated from materials employed to stuff the mummies showed cellulolytic activities, such as those related to species of the genera Chromohalobacter and Nesterenkonia, as well as those identified as Staphylococcus equorum and Halomonas sp. Furthermore, many of the strains were pigmented ranging from yellow to a strong pink color, being directly related to the discoloration displayed by the materials.

Fig. 1

Mummies displayed along the walls of the Capuchin Catacombs of Palermo, Italy (pictures: Sterflinger)

Fig. 2

a Water migrating horizontally into the walls of the Catacombs. b Salt crusts of sodium chloride on the walls. c Detached salt contaminating other materials (pictures: Sterflinger)

Fig. 3

a Sample W1: rosy discolored wall. b Sample W2: salt efflorescence with yellowish discoloration. c Sample PS: wall showing purple stains. d Sample C3: stuffing material, showing orange to rosy discoloration (pictures: Sterflinger)

Fig. 4

RAPD-PCR patterns of representative strains isolated from a 3 % NaCl, b 10 % NaCl, and c 20 % NaCl media. The number of lanes indicates the number of the strains. Lanes M 1 kb ladder (Fermentas)