## 1 Introduction  
The use of stone as a building material in monuments and artworks is an ancient practice and much of our built heritage is based on this type of material, given its abundance, mechanical and decorative properties and, especially, its durability. Limestone, a sedimentary rock characterized by high levels of calcium carbonate (CaCO\({}_{3}\)), due to its properties and abundance in Portugal, particularly on the central coast, has been widely used in construction, both as a structural and as a decorative material [1]. The weathering of rocks, a fundamental step in the cycles of minerals on our planet, can become an inconvenient process with serious consequences when it affects stone used in construction [1, 2]. This is a more pressing and relevant fact in buildings with historical and cultural value, resulting in immeasurable losses [3]. For several decades, the role of microorganisms in the deterioration of the cultural heritage was neglected, with emphasis being placed mainly on the effect of environmental and chemical factors. Recently, numerous studies have been carried out focusing on the relationship between microorganisms and stone monuments, revealing their relevance in the processes of deterioration of materials used in assets with historical and cultural value [4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18]. Nevertheless, it is impossible to separate the biological action from the physicochemical factors [19]. These agents act together, and in close relation, in an antagonistic or synergistic way, in the deterioration of the stone [1; 2]. In this combined process, their relative importance varies with factors such as environmental conditions, the type of substrate, the state of conservation and location in the monument [20]. Colonization by microorganisms and subsequent biodeterioration, especially in the outdoors, cannot be controlled and is markedly influenced by climate and location [21]. However, in indoor environments, it is mainly influenced by human occupation and associated activities and can (to a certain extent) be controlled, particularly by managing lighting, heating, humidity, and ventilation [21; 22]. The existence of water on the stone surface is considered one of the most determining factors in the occurrence of these phenomena [21; 23]. Fungi are considered one of the most important stone colonizers [24]. They are ubiquitous heterotrophic organisms, metabolically more versatile than other biodeteriogenic agents, a characteristic that allows them to colonize a wide range of substrates, such as wood, metal, and stone, among others. The ability to grow on different substrates, resist extreme environmental conditions and adopt different structural, morphological, and metabolic strategies, makes them highly adaptable organisms capable of thriving in in-hospitable environments [25]. They are particularly active in the biodeterioration of rock through several physical and chemical mechanisms, often with synergistic action, that can result in pitting, mineral dislocation, dissolution and reprecipitation [3; 6; 21; 24; 26; 27]. Additionally, besides the ability to deeply alter stone integrity and structure, some fungi produce pigments (e.g., melanin) that cause chromatic alteration of the rock, an effect considered unaesthetic [6; 26; 27; 28; 29]. Limestones are carbonate rocks with a high intrinsic bioreceptivity, being especially prone to microbial colonization and, consequently, to biodeterioration phenomena. Anca limestone, a subtype of limestone often used in Portuguese monuments, has the highest primary bioreceptivity among different Portuguese lithotypes [17]. Very few studies have been conducted targeting fungal colonization in this particular subtype of limestone, but [PERSON] et al. [16] revealed highly diverse fungal communities in this lithotype, that play an active role in the biodeterioration processes. Until recently, most information available on the colonization of cultural property by microorganisms came from the use of classical microbiology methodologies.