# Current Knowledge on the Fungal Degradation Abilities
## 1 Introduction  
The Fungal Kingdom comprises a highly diverse eukaryotic group able to inhabit every ecological niche available on the Planet [1]. The growth and biological activity of fungal species in cultural heritage materials is known to develop serious damages by means of biodetorioration (the undesirable modifications of a valuable material occurring by the action of living organisms) [2, 3]. Fungi are highly versatile, ubiquitous, chemoheterotrophic microorganisms, being able to grow in a vast number of materials and contributing to the development of various biodeterioration phenomena [2, 3]. Such modifications are a result from fungal species settling, development and exploitation of various organic and inorganic compounds present in historic art-pieces and monuments [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]. The fungal biodeterioration of books, paper, parchment, textiles, photographs, paintings, sculptures and wooden materials occurs due to the aesthetic modifications, mechanical pressure and exoenzymatic action [2]. Various components of these materials such as cellulose, collagen, linen, glues, inks, waves and organic binders can be oxidized, hydrolyzed, dissolved, stained or structurally modified as a result of the action of fungal enzymes, pigments and organic acids [2, 3, 7, 8, 9, 10, 11]. A typical and widely known example of these phenomena is known as \"foxing\", the development of red-brownish localized spots, hypothesized to be a result from fungal proliferation and metabolization of organic acids, oligosaccharidesrides and proteic compounds that can stain and modify the constituent materials of many paper-based and photographic supports [3, 8, 13]. Another example of microorganism's attack of organic materials is related to the biodeterioration of human remains, mummies and funery materials, where opportunistic, saprotrophic and highly cellulolytic and proteolytic taxa are able to thrive and trough their actions severely alter them [2, 14, 15]. Complementarily, historic relics mainly composed of inorganic components such as stone,frescoes, glass and ceramics can also suffer deep aesthetical, physical and chemical modifications resulting from fungal grow and action [2; 3; 4; 5; 6; 12; 16]. In these supports, deterioration is caused by hyphae penetration into the substrate, the production and release of extracellular destructive organic acids, enzymes and metabolites and by the the formation of distinct colored outlines as a result of fungi high pigment contents, contribution to biofilm development and chemical reactions with inorganic compounds [2; 3; 4; 5; 6]. Due to the known biodeterioration problems arising from their proliferation, the accurate species identification and a consequent deteriorative profiling of isolates are crucial steps towards the development and the establishment of proper protective measures for the diverse cultural heritage treasures around the world. With the recent development of innovative culture independent methodologies such as -omics technologies, molecular data is becoming increasingly more valuable for the identification of the microbes, the characterization of their metabolic functions and their deteriorative byproducts [17]. Methodologies such as metagenomics, transcriptomics, metabolomics and proteomics revolutionized the field and are increasingly allowing understanding of microbial diversity, but also species specific and holistic contributions to various materials biodeterioration phenomena [17]. These methods are particularly relevant considering that traditional cultivation dependent methodologies hold the disadvantage of being unable to correctly infer microorganism's abundance and only allow the study of active forms, failing to provide information regarding viable non-culturable and non-viable forms [17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27].