## 3 Results
### Wood Deterioration  
SEM image in Figure 6a is a transverse section of _Acacia nilotica_ standard sample. This diffuse-porous wood is characterised by solitary or multiples vessels. Axial parenchyma was vasicentric, aliform lozenge-aliform, and confluent where the homogeneous structure of wood cell walls clearly appeared. On the contrary, the ancient wood sample #1 (Figure 6b) showed an advanced decay in which a wide wood fragmentation was visible. Cell walls look collapsed, and cracked vessels and voids were clearly observable. This led to a porosity and fragility of the wood structure. Such wood cells separations might be attributed to the collapse of middle lamella region that leads to reduction in the homogeneity of the wood structure, causing either fracture or evacuation and cell wall erosion [63]. XRD patterns of the standard sample compared with sample #1 from (2\(\Theta\)) 5\({}^{\circ}\) to 30\({}^{\circ}\) are displayed in Figure 7a. The standard sample shows two diffraction peaks at (2\(\Theta\)) 15.5\({}^{\circ}\) (101) and 22.2\({}^{\circ}\) (200), characteristic of the _Acacia nilotica_ natural fibres [64]. The aforementioned two peaks are attributed to the cellulose I typical crystallographic plane. In sample #1, the intensity of the two above-mentioned main peaks strongly decreased, while a further weak peak appeared at (2\(\Theta\)) 18.04\({}^{\circ}\), that is, the minimum intensity between the above-mentioned peaks; it is usually attributed to the amorphous fractions of lignin, pectins, hemicellulose, and amorphous cellulose. Figure 5: (**a,b**) SEM images (magnification 3000\(\times\)) of sample #1 (pure core wooden sample, inner the statue). Fungal hyphae (panel (**a**)) and spores (panel (**b**)) are visible. (**c,d**) Images of FISH assays under the epifluorescence microscope using the DAPI-stain for all microbial cells (blue, panel (**c**)) and the Cy3-labelled EUB probe for _Bacteria_ (red, panel (**d**)) (magnification 1000\(\times\)). Figure 6: (**a**) SEM image of the _Acacia_ standard wood sample (magnification 600\(\times\)); red arrows indicate the homogeneous structure of wood cell walls. (**b**) SEM image of the sample #1 (Pure core wooden sample; magnification 800\(\times\)). The red arrows indicate the strongly fragmented wood structure. Figure 7: (**a**) XRD patterns of the standard wood sample (thicker upper line) and of the archaeological wood sample #1. (**b**) Average spectra extracted from the FPA images of _Acacia_ standard sample (black line), sample #1, and sample #2 (red and violet lines, respectively). The coloured rectangles highlight the infrared features of interest for cellulose (§), lignin (#), and deterioration products (**v**) (green, orange, and blue, respectively). (**c**–**e**) Optical images (15\(\times\)) of the _Acacia_ standard sample (**c**), sample #1 (**d**), and sample #2 (**e**), obtained with the VIS-IR microscope. The crystallinity index (CrI %), calculated by means of the Segal empirical method, was found to be 67.2% for the _Acacia_ standard sample and 37.7% for the sample #1. The crystallinity index in sample #2 was not measured because the very high amount of inorganic material did not allow to obtain a significant result. The optical images of the _Acacia_ standard sample and the ancient wood samples #1 and #2 collected by the infrared microscope are shown in Figure 7c-e. The _Acacia_ standard sample showed a clear colour and a homogeneous appearance. Well-preserved parallel wood fibres were observed, even after the compression of the sample in the diamond cell. The ancient samples, on the contrary, showed a deep brown/reddish colour and an amorphous appearance, and wood structures were not distinguished, also due to the preparation of the sample (its compression in the diamond cell). Figure 7b shows the average spectra of the _Acacia_ standard (pink line) and the two fragments of ancient wood samples #1 and #2 (green and red lines, respectively) in the fingerprint region (1900-900 cm\({}^{-1}\)).