Synergistic nitrogen-sulfur metabolism driving biodeterioration revealed by metagenomic and DNA-SIP analyses at the Chen Cihong residence

Abstract Acid attack on stone cultural heritage is intrinsically linked to microbially driven nitrogen and sulfur cycling, yet the precise acid-producing metabolic machinery remains elusive. By integrating amplicon sequencing, DNA-stable isotope probing (DNA-SIP) and metagenomics, this study unveils a novel synergistic mechanism. A predominance of Candidatus Nitrocosmicus (AOA) and Nitrosospira (NOB) was found on the stone. Following 15 N incubation, active nitrification was confirmed by increased amoA and nxrB gene abundance and the production of 15 NO 2 ⁻ and 15 NO 3 ⁻. Furthermore, elevated norB and nosZ gene levels, alongside 15 NO 2 ⁻ and 15 NO 3 ⁻ depletion, confirmed an active denitrification. Concurrently, Dissimilatory Nitrate Reduction to Ammonium (DNRA) supplied the substrate by ammonia-oxidization, driving an internal nitrogen cycle. Crucially, metagenomics revealed coupling between denitrification and sulfur oxidation, demonstrating a synergistic cycle that accelerates acid production and salt damage. These findings establish a probable link between coupled nitrification-denitrification-sulfur oxidation and stone decay, providing a new conceptual framework for developing targeted biostatic strategies.