Metagenomic insights into microbial biodeterioration of terracotta in the 18th-century-old temple Jor Mandir.

Abstract

Microbial colonisation represents a significant yet underexplored factor contributing to the biodeterioration of terracotta heritage structures in tropical environments. Here, we present a comprehensive multi-analytical investigation of the Jor Mandir complex, an eighteenth-century terracotta monument in eastern India. Culture-based analysis revealed morphologically distinct cyanobacteria that were not detected by metagenomics, underscoring the complementarity of the two approaches. Amplicon sequencing of a composite biofilm sample revealed a microbial community dominated by Cyanobacteria (44.18%), followed by Actinobacteriota (18.61%), Proteobacteria (14.30%), Chloroflexi (10.16%), Acidobacteriota (7.38%), and other minor phyla. Stress-tolerant coccoid taxa such as Chroococcidiopsis and Aphanocapsa, along with filamentous genera including Leptolyngbya, Lyngbya, Oscillatoria, and Phormidium, and heterocystous nitrogen-fixing genera such as Scytonema, Nostoc, and Calothrix, were identified. These organisms exhibited biochemical adaptations, including the production of scytonemin and carotenoids, which contributed to photoprotection and substrate weathering. Elemental profiling indicated associations between the aluminosilicate terracotta matrix and surface-associated biofilm material. GC-MS analysis revealed a range of organic compounds, including fatty acid methyl esters, hydrocarbons, phenolic compounds, and phthalate derivatives, reflecting the chemically complex nature of the biofilm matrix. PICRUSt2-based functional reconstruction further indicated a biofilm community with predicted pathways related to biosynthetic processes, biodegradation pathways, and energy metabolism. Together, these descriptive observations provide a site-specific baseline profile of microbial colonisation and biofilm-associated characteristics on the terracotta surfaces of the Jor Mandir complex and highlight the value of integrating microbiological and physicochemical approaches in future monument monitoring and conservation studies.