Vol.:(0123456789) 1 3 Facies (2019) 65:18 https://doi.org/10.1007/s10347-019-0564-5 ORIGINAL ARTICLE Study of the euendolithic activity of black meristematic fungi isolated from a marble statue in the Quirinale Palace’s Gardens in Rome, Italy Filomena De Leo 1  · Federica Antonelli 2  · Anna Maria Pietrini 3  · Sandra Ricci 3  · Clara Urzì 1 Received: 4 September 2018 / Accepted: 1 March 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract The present study analyzed the dark patina present on the surface of a marble statue exposed in the Gardens of the Quirinal Palace in Rome, with a special focus on euendolithic black meristematic fungi. The study of the spatial distribution of micro- organisms and their identification were performed by using a multistep approach based on microscopy, cultural analyses, molecular techniques, and embedding resin-casting technique. Black meristematic fungi were observed in the patina. Since morphological features are not sufficient to identify fungi belonging to this group, cultural and molecular analyses were performed. The results highlighted the presence of the species Coniosporium apollinis and of strains related to the genus Knufia (order of Chaetothyriales). The resin-casting embedding technique demonstrated the active penetration of these fungi into the marble grains, thus documenting their true endolithic behavior. The involvement of phototrophic microorganisms present on the surface in the active penetration of the marble was excluded. Keywords Resin embedding-casting technique · Bioerosion · Euendolithic fungi · MCF · Coniosporium apollinis · Knufia Introduction Biological greyish-black patina is one of the most common subaerial biofilms (SAB) widespread on the surfaces of cal- careous substrates and responsible for serious phenomena of biodeterioration of outdoor exposed artworks all over the world (Anagnostidis et al. 1983; Diakumaku et al. 1995; Wollenzien et al. 1995; Gorbushina 2007; Sterflinger 2010; Pinna 2017). Harsh environmental conditions of the stone surface (high solar radiation, scarce water supply, lack of nutrients, fluctuating temperatures, etc.) select a highly versatile group of microorganisms, mainly belonging to cyanobacteria, microalgae, and microfungi. However, the relationship between substrate and species composition varies depending on the environmental factors (e.g., light, water availability, presence of vegetation, etc.), the lithotype, the state of preservation of the substrate, and the different microhabitats present in the artifact (De Leo et al. 1996; Gorbushina 2007; Zakharova et al. 2013; De Leo and Urzì 2015; Isola et al. 2015; Salvadori and Municchia 2016). Very often, black fungi are the only inhabitants of the dark patinas on the rocks (Gorbushina 2003; Urzì 2004). They include ubiquitous hyphomycetes of soil and epiphytic origin that are dominant under favorable environmental con- ditions (e.g., high humidity, abundant nutrients, mild tem- peratures, etc.) and the group of so-called microcolonial fungi (MCF), well adapted to survive and even to grow in extremely harsh and hostile environments such as bare rocks in desert both in hot and cold climates (Staley et al. 1982; Selbmann et al. 2005, 2008; Sterflinger et al. 2012; Salvadori and Municchia 2016). MCF, also known as black meristematic fungi, are charac- terized by isodiametric cell wall expansion concomitant with ongoing cytokinesis and arbitrarily oriented septation (de Hoog et al. 1999). Sometimes, polarized growth featuring This article is part of a Topical Collection in Facies on Bioerosion: An interdisciplinary approach, guest edited by Ricci, Uchman, and Wisshak. * Filomena De Leo fdeleo@unime.it 1 Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale F. Stagno d’Alcontres, 31, 98166 Messina, Italy 2 Department of Innovation of Biological Systems, Food and Forestry (DIBAF), Tuscia University, S. Camillo de Lellis snc, 01100 Viterbo, Italy 3 Biology Laboratory, ISCR, Istituto Superiore per la Conservazione e per il Restauro (ISCR), Via di San Michele, 25, 00153 Rome, Italy