Bacterial degradation of sandstone at the UNESCO World Heritage Site Rani-ki-Vav, India: A multi-analytical diagnostic study

Rani ki Vav, a UNESCO World Heritage stepwell in India, exhibits progressive sandstone decay through granular disintegration, and biofilm encrustation. This study integrates mineralogical, metabolomic, and microbiome analyses to resolve in situ biodeterioration pathways. XRD and FTIR identified quartz as dominant phase, with acid-sensitive minerals like kaolinite, and calcite susceptible to dissolution. LC-MS/MS and GC–MS/MS identified a diverse metabolite pool, including organic acids (glycolic acid, vanilpyruvic acid), nitrogen and sulfur species (cyanuric acid, sulforaphane; L‑serine O-sulphate), metal-chelating peptides and their derivatives (cysteinyl‑serine; L-homocitulline), and hydrophobic long-chain compounds. 16S rRNA profiling shows a community dominated by Firmicutes 61.49%, Bacteroidetes 18.53%, Proteobacteria 18.18%, Actinobacteria 1.38%, Cyanobacteria 0.35%. These findings suggests a potential degradation pathways includes (i) biofilm derived moisture retention; (ii) organic and inorganic acid attack on calcite and aluminosilicates; (iii) chelation of Ca +2 , Fe +3 and Al +3 and ion loss; (iv) hydrophobic-patch-induced differential drying and salt crystallization; (v) micro fracturing and exfoliation. Together, multi-instrument dataset reveals a coupled sequence of microchemical processes including acidification, chelation, biofilm-mediated moisture retention, and crystallization pressure that collectively weaken the sandstone matrix. This study demonstrates how integrated spectroscopy and mass spectrometry can elucidate biochemically driven mineral transformations, providing a chemical basis for developing targeted conservation strategies for sandstone heritage.