Alternaria tenuissima, a biodeteriogenic filamentous fungus from ancient Oplontis ruins, rapidly penetrates tuff stone in an in vitro colonization test

To integrate the understanding of mycological biodeterioration on artistic-historical heritage, we cultivated Alternaria tenuissima on Neapolitan Yellow Tuff (NYT) tiles for 20 d in a low-carbon environment. The fungus, collected within the UNESCO site of ancient Oplontis ruins (Naples, Italy), was monitored during its early colonization both for the epilithic and the cryptoendolithic growth by using photomicrography-based image analyses. The data were integrated with the count of conidia and the analysis of biochemical proxies in order to evaluate the biological status of the fungus during growth. Additionally, we provided novel and synthetic insights on A. tenuissima 3D growth dynamics, suggesting that visible fungal spots on stone monuments could represent the “iceberg tip” for advanced stone decay. Our results confirm that in vitro tests, coupled with microscopical observations and computer image analysis, are useful tools to evaluate and quantify fungal biomass on a stone substratum, especially in the early steps of fungal colonization.