## 3 Results
### Distribution and Identification of the Isolated Fungi  
A total of 186 fungal colonies were recovered from Muong Cultural Space Museum (\(n=49\)), Museum of Biology (\(n=73\)), and Thu Museum (\(n=64\)) samples. Analysis of morphological and spore features of fungal isolates primarily classified them into 40 distinct clusters (Figure 2). Specifically, the most remarkable diversity and highest abundance of fungal species were found in Thu Museum samples (\(n=18\)), followed by the Muong Cultural Space Museum samples (\(n=16\)) and Museum of Biology samples (\(n=6\)). Notably, at least three different fungal species were found in each glass sample, indicating co-contamination. Thus, the disinfection of fungal-contaminated optical equipment would face a significant challenge.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Place**} & \multirow{2}{*}{**Glass Sample**} & \multicolumn{2}{c}{**Evaluation of the Extent of Fungal Growth *} \\ \cline{3-4}  & & **Hyphal Surface Coverage (\%)** & **Harmful Grade** \\ \hline \multirow{4}{*}{Muong Cultural Space Museum,} & BXMA1 & \(29\pm 1.2\) & 2 \\  & BXMA2 & \(35\pm 1.5\) & 3 \\  & BXMA3 & \(26\pm 1.3\) & 2 \\  & BXMA4 & \(21\pm 1.2\) & 2 \\  & BXMA5 & \(21\pm 1.5\) & 2 \\ \hline \multirow{4}{*}{Museum of Biology,} & BTBB1 & \(28\pm 1.5\) & 2 \\  & BTBB2 & \(41\pm 1.7\) & 3 \\  & BTBB3 & \(27\pm 1.6\) & 2 \\  & BTBB4 & \(43\pm 2.1\) & 3 \\  & BTBB5 & \(48\pm 1.4\) & 3 \\ \hline \multirow{4}{*}{Thu Museum, Vinh} & BMLC1 & \(41\pm 1.6\) & 3 \\  & BMLC2 & \(36\pm 1.8\) & 3 \\ \cline{1-1}  & BMLC3 & \(34\pm 1.6\) & 3 \\ \cline{1-1}  & BMLC4 & \(25\pm 1.3\) & 2 \\ \cline{1-1}  & BMLC5 & \(43\pm 2.2\) & 3 \\ \hline \hline \end{tabular}
*ISO 902-11 interpretation for the coverage of a glass surface with fungal hyphae: \(>\)0 to 10\(\%\) (Grade 1)—restricted fungal growth; \(>\)10 to 30\(\%\) (Grade 2)—intermittent spread fungal colonies (visible with the naked eye); \(>\)30 to 70\(\%\) (Grade 3)—a substantial amount of fungal growth (easily visible); \(>\)70\(\%\) (Grade 4)—massive fungal growth.  
\end{table}
Table 1: The extent of fungal hyphae on eyepiece samples.  
Figure 1: (**a**) The binocular model. (**b**) Binocular eyepieces contaminated with fungi. (**c**) Image captured using light microscopy at a magnification of 60\(\times\). (**d**) The estimation of hyphae covering the glass surface treated by the ImageJ tool. (**e**) SEM image exhibiting the fungal growth and colonization on the eyepieces (image at a magnification of 1000\(\times\), scale bar = 10 \(\upmu\)m). (**f**) Yellow arrows indicate fingerprinting/etching of fungal hyphae on the surface of eyepieces after the cleaning procedure (image at a magnification of 2000\(\times\), scale bar = 10 \(\upmu\)m).  
The molecular identification based on the ITS sequencing revealed high similarities (between 99 and 100%) to known fungal species belonging to 14 genera, including _Penicillium, Byssochlamys, Talaromyces, Cladosporium, Photopsis, Neopestalotiopsis, Trichoderma, Copriellus, Perenniporia, Curvularia, Pithonyces, Pseudopithomyces,_ and _Apergillus_ (Figure S1). _Apergillus_ (43.8%) and _Penicillium_ (31.3%) were the two predominant fungal genera, followed by species of the genus _Curvularia_ (4%). The comparative sequence analyses combined with the clustering tree analysis further allowed us to assign 40 different fungal species (Figure S1). Fungal strains distributed throughout the tree in multiple single branches demonstrate high genetic diversity in both local and regional scales.