Basile Arianna, Riggio Filippo Pasquale, Tescari Marco, Chebbi Alif, Sodo Armida, Bartoli Flavia, Imperi Francesco, Caneva Giulia, Visca Paolo
Department of Science, Roma Tre University, Viale G. Marconi 446, 00146 Rome, Italy.
Department of Science, Roma Tre University, Viale G. Marconi 446, 00146 Rome, Italy; Biology Laboratory, Supporto ALES S.p.A. c/o Istituto Centrale per il Restauro (ICR), Via di S. Michele, 25, 00153 Rome, Italy.
Sci Total Environ. 2025 Jan 1;958:178135. doi: 10.1016/j.scitotenv.2024.178135. Epub 2024 Dec 19.
Pink biofilm formation on stone monuments and mural paintings poses serious harm to cultural heritage preservation. Pink biofilms are globally widespread and recalcitrant to eradication, often causing recurrences after restoration. Yet, the ecological drivers of pink biofilm formation and the metabolic functions sustaining the growth of pigment-producing biodeteriogens remain unclear. In this study, a combined approach integrating physicochemical investigations, scanning electron microscopy, 16S rRNA sequence-based analysis of the prokaryotic community, metagenomic deep sequencing, and metabolic profiling, was applied to determine the etiology of rosy discoloration of ancient frescoes in the Gelati and the Martvili Cathedrals (Georgia). Martvili samples showed greater diversity than Gelati samples, though Actinomycetota predominated in both samples. Rubrobacter-related sequences were detected in all sampling sites, showing an overwhelming abundance in Gelati samples. Reconstruction of metagenome-assembled genomes (MAGs) and phylogenetic analyses highlighted significant intra-genus diversity for Rubrobacter-related sequences, most of which could not be assigned to any formally described Rubrobacter species. Metabolic profiling of the Gelati metagenomes suggests that carbon-fixing autotrophic bacteria and proteinaceous substances in the plaster could contribute to sustaining the chemoorganotrophic members of the community. Complete pathways for β-carotene and bacterioruberin synthesis were identified in Rubrobacter MAGs, consistent with the Raman spectroscopy-based detection of these pigments in fresco samples. Gene clusters for the synthesis of secondary metabolites endowed with antibiotic activity were predicted from the annotation of Rubrobacter MAGs, along with genes conferring resistance to several antimicrobials and biocides. In conclusion, genome-resolved metagenomics provided robust evidence of a causal relationship between contamination by Rubrobacter-related carotenoid-producing bacteria and the rosy discoloration of Georgian frescoes, with relevant implications for rational biodeteriogen-targeted restoration strategies.
石碑和壁画上粉色生物膜的形成对文化遗产保护造成了严重危害。粉色生物膜在全球广泛分布且难以根除，修复后常复发。然而，粉色生物膜形成的生态驱动因素以及维持产色素生物劣化剂生长的代谢功能仍不清楚。在本研究中，采用了一种综合方法，包括物理化学研究、扫描电子显微镜、基于16S rRNA序列的原核生物群落分析、宏基因组深度测序和代谢谱分析，以确定格鲁吉亚 Gelati 和 Martvili 大教堂古代壁画玫瑰色变色的病因。Martvili 样本的多样性高于 Gelati 样本，尽管放线菌门在两个样本中均占主导地位。在所有采样点均检测到与红杆菌相关的序列，在 Gelati 样本中含量极高。宏基因组组装基因组（MAG）的重建和系统发育分析突出了与红杆菌相关序列的显著属内多样性，其中大多数无法归入任何正式描述的红杆菌物种。Gelati 宏基因组的代谢谱分析表明，石膏中的固碳自养细菌和蛋白质物质可能有助于维持群落中的化学有机营养成员。在红杆菌MAG中鉴定出了β-胡萝卜素和细菌红素合成的完整途径，这与壁画样本中基于拉曼光谱对这些色素的检测结果一致。从红杆菌MAG的注释中预测了具有抗生素活性的次生代谢物合成基因簇，以及赋予对几种抗菌剂和杀生物剂抗性的基因。总之，基因组解析宏基因组学为与红杆菌相关的产类胡萝卜素细菌污染与格鲁吉亚壁画的玫瑰色变色之间的因果关系提供了有力证据，这对合理的针对生物劣化剂的修复策略具有重要意义。
