## 2 Results and Discussion
### Determination of the Modes of Action of EOEP on B. cereus Using Synchrotron FTIR Microspectroscopy
#### 2.4.2 Principal Component Analysis (PCA) of the FTIR Spectra from \(B\). cereus Treated with EOEP  
We conducted PCA to justify this multivariate data set and differentiate changes between untreated cells and treated cells. Here, we showed clear data segregations between untreated cells and treated cells of the scores for the PC1 (variability; 60%) and PC2 (variability; 23%), as shown in Figure 5. The PCA score plot shows that spectra from a cell treated with 0.1% EOEP for 0, 6 and 12 h on \(B\). _cereus_ can be clustered separately along PC1 and PC2. Moreover, a grouping of the spectra represents significant differences between untreated (0 min) and treated cells (6 and 12 h) that can be correlated with changes in the molecular composition of \(B\). _cereus_, including fatty acid (2925 cm\({}^{-1}\)), protein (1630 cm\({}^{-1}\)), and mixed region, which characterizes the cell membrane and DNA/nucleic acids (1240 and 1085 cm\({}^{-1}\)). The PCA results correspond to the time-kill assay, as previously described, as the EOEP at concentration 0.1% showed bactericidal effect against \(B\). _cereus_ within 6 h and continuously throughout 12 h. Interestingly, the negative and positive spectral variations indicated by the PC1 and PC2 loading plots that were oppositely correlated to each other at 1630 cm\({}^{-1}\) may indicate a higher level of amide I of \(\beta\)-pleated sheet structures in the proteinaceous content of treated cells compared to untreated cells. Additionally, the oppositely correlated PC1 and PC2 at 1240 and 1085 cm\({}^{-1}\) may reflect considerable level of nucleic acids, DNA and RNA of the treated and untreated cells. Our findings reveal the mode of action of the EOEP targeted on the phosphodieser of the nucleic acids, including DNA and RNA and the proteinaceous substances of cells, in particular, amide I.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Wave**} & \multirow{2}{*}{**Possible Biomolecule Contributors**} & \multicolumn{2}{c}{**Contact Time**} & \multirow{2}{*}{**References**} \\ \cline{3-4}  & & 0 h & 6 h & 12 h \\ \hline
3295 & Amid A in Proteins & 246.37 \(\pm\) 0.01b & 475.86 \(\pm\) 0.06a & 414.12 \(\pm\) 0.01a & [36,38] \\
2925 & Fatty acids & 159.49 \(\pm\) 0.01c & 299.66 \(\pm\) 0.03a & 274.81 \(\pm\) 0.01b & [36,37,39] \\
2851 & Fatty acids & 107.39 \(\pm\) 0.00b & 190.44 \(\pm\) 0.02a & 177.77 \(\pm\) 0.01a & [35,37] \\
1650 & Proteinaceous content of cell & 340.63 \(\pm\) 0.02c & 398.52 \(\pm\) 0.10a & 808.40 \(\pm\) 0.05b & [32,37,40] \\
1630 & Proteinaceous content of cell & 272.01 \(\pm\) 0.005e & 609.91 \(\pm\) 0.07a & 514.76 \(\pm\) 0.03b & [32,37,41] \\
1541 & Proteinaceous content of cell & 221.51 \(\pm\) 0.01b & 572.58 \(\pm\) 0.06a & 493.14 \(\pm\) 0.03a & [37,41,42] \\
1444 & Cell membrane (lipids, proteins) & 79.61 \(\pm\) 0.00b & 211.66 \(\pm\) 0.02a & 189.53 \(\pm\) 0.01a & [35,43] \\
1400 & Cell membrane (amino acids, fatty acids) & 89.56 \(\pm\) 0.01b & 244.34 \(\pm\) 0.03a & 215.35 \(\pm\) 0.01a & [36,37,44] \\
1240 & Phosphodiesters in nucleic acid & 69.24 \(\pm\) 0.01b & 277.30 \(\pm\) 0.03a & 245.85 \(\pm\) 0.01a & [37,45] \\
1085 & DNA and RNA, phospholipids & 92.20 \(\pm\) 0.00b & 334.54 \(\pm\) 0.04a & 308.73 \(\pm\) 0.01a & [32,37,45] \\ \hline \hline \end{tabular} Values are given as mean \(\pm\) standard deviation. a–b Different letters in the same row indicate significant differences between the means obtained in [PERSON]’s test (\(p\leq 0.05\)).  
\end{table}
Table 3: Band area (\(\times\) 10\({}^{-3}\) cm\({}^{-1}\)) and band area changes of \(B\). _cereus_ treated with 0.1 % \(\forall\)/\(\forall\) of EOEP.