# FTIR Spectroscopy for Identification and Intra-Species Characterization of _Serpula Iacrymans_
## 1 Introduction  
_Serpula Iacrymans_ is a Basidiomycota of the order Boletales, which is the main agent of brown rot in buildings and historical monuments in Europe, Russia, North America, and Japan [1, 2, 3, 4, 5]. _S. lacrymans_ is rarely detected alone in a building; other wood-degrading fungi accompany it which makes its detection difficult [6, 7]. The observation of brown rot and the analysis of the mycelium and fruiting bodies can direct the identification of wood-damaging fungi to a presence of _S. lacrymans_[8]. When the fruiting bodies or microstructures of the mycelial cords (rhizomorph) characteristic of _S. lacrymans_ cannot be found, a sample must be taken. Two identification approaches are then possible: a classical agar culture technique or a molecular biological approach. The cultivation of the fungus on a nutrient agar medium allows for the specification of its macro and microscopic morphological characters. The main advantage of this cultural approach is low cost, but it is time-consuming and tedious, requires strong expertise, and may not be very discriminating for the related species [3, 9]. As the cultivation of _S. lacrymans_ from samples is often unsuccessful, a molecular biological approach is of interest. Polymerase chain reaction (PCR) amplification and the sequencing analysis of molecular markers in the internal transcribed spacer (ITS) region can identify fungi with varying degrees of discrimination depending on the taxonomical group considered [10]. The universal primer pair, ITS1 andITS4, is used generically for fungal identification; the primer pair, ITS1-F and ITS4-B, can be used to specifically highlight Basidiomycota, and the _S. lacrymans_-specific SL primer can be combined with ITS1 to detect this species [11; 12; 13]. The advantage of this method is that it allows the identification of a fungus regardless of its developmental stage [14]. However, some published studies using species-specific primers to detect _S. lacrymans_ from environmental samples recorded some failures [6; 7; 15].  
Fourier transform infrared spectroscopy (FTIR) is an alternative technique for the characterization and identification of different types of microorganisms, particularly fungi [16; 17; 18; 19; 20]. FTIR is based on the acquisition of a specific spectral signature of each microorganism after cultivation under given conditions. This spectral signature corresponds mainly to the composition of proteins, lipids, nucleic acids and carbohydrates in the biomass. The vibrational spectra of different fungal species have many signals in common and contain a large number of variables requiring the coupling to multivariate statistical analysis methods for their comparison [20]. The reproducibility of FTIR for fungal identification requires the standardization of each step of the analytical protocol: culture conditions, sample preparation and spectral acquisition parameters [21].  
Several protocols using FTIR spectroscopy have been described to identify moulds [19; 20; 22; 23; 24; 25]. Only a few studies have used FTIR to identify wood-decay fungi, but none to identity _S. lacrymans_[26; 27]. In this study, we used different fungal growth conditions and different mycelial harvesting methods to select the best protocol for the identification of _S. lacrymans_ by Attenuated total reflectance (ATR)-FTIR spectroscopy. The goal of this study was to standardize, optimize, and show that FTIR spectroscopy is a suitable method for the identification and discrimination of different strains of _S. lacrymans_.