## 3 Results
### FTIR Analysis  
By means of FTIR analysis, it was possible to determine the biochemical and structural differences that were present in the investigated bacilli.  
In the obtained spectra, based on the work of [PERSON] et al. [19], the peak wavenumbers were assigned [19] (Table 1).  
Figure 2 reports both the structural similarities and the differences between the regions of the spores obtained from the studied bacilli that were investigated in the FTIR spectra.  
In the region referring to lipids and amide III (2800-3000 cm\({}^{-1}\)), peaks were present at 2854 and 2940 cm\({}^{-1}\) for the SBP3 spore spectrum, at 2852 and 2938 cm\({}^{-1}\) for the BHO spore spectrum and at 2850 and 2925 cm\({}^{-1}\) for the BSU spore spectrum.  
In the region of amide I, attributed to amino acids and polypeptides (1560-1660 cm\({}^{-1}\)), evident peaks were present at 1630 and 1620 cm\({}^{-1}\) in the SBP3 and the BHO spectra, respectively, and at 1655 cm\({}^{-1}\) in the BSU spectrum, suggesting different spore protein structures.  
The frequency of the peaks attributable to the ring vibrations of carbohydrates (1000-1250 cm\({}^{-1}\)) differed from each other, suggesting that each spore possesses a unique carbohydrate structure as well as that in the nucleic acid bands (900-1000 cm\({}^{-1}\)).  
Figure 1: Scanning electron micrographs (bar: 1 \(\upmu\)m) of spores from (**A**) \(B\). _horneckiae_ SBP3, (**B**) \(B\). _horneckiae_ DSM 23495T and (**C**) \(B\). _subtilis_ 168. Arrows indicate the exosporium layer.  
The FTIR analyses, coupled with the wavelet analysis of spectra from SBP3, BHO and BSU spores, are shown in Figure 3.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Wavenumber Values (cm\({}^{-1}\))** & **Band Assignment** & **References** \\ \hline \multicolumn{3}{c}{H-bond and OH group of alcohol, phenols and} \\
3300–3200 & organic acid including nucleic acids and & [20] \\  & proteins amide A & \\
3100–3000 & n(C-H) of cis C=H bonds & [21] \\ \(\sim\)2925 & Lipids & [21] \\
1700–1750 & Protein and esters of muramic acid and ester & [22] \\  & fatty acid group & \\
1660–1628 & Amide I peptitic conformation & [23] \\ \(\sim\)1548 & Amide II peptitic conformation & [24] \\ \(\sim\)1380 & CH\({}_{2}\) and CH\({}_{3}\) bending from lipids, DPA amide III & [25] \\ \(\sim\)1066 & Ring vibrations of carbohydrates & [21] \\ \(\sim\)966 & CH conjugated trans, trans isomers & [26] \\ \(\sim\)780 & Nucleic acids, sugar-phosphate vicration & [27] \\ \hline \hline \end{tabular}
\end{table}
Table 1: FTIR band assignments for the functional groups according to [PERSON] et al. [19].  
Figure 3: Comparison among FTIR spectra using the coefficient of the wavelet correlation between spores: (**A**) _B. subtilis_ (BSU) 168 vs. _B. horneckiae_ SBP3(SBP3); (**B**) _B. horneckiae_ DSM 23495\({}^{\text{T}}\) (BHO) vs. _B. horneckiae_ SBP3; and (**C**) _B. subtilis_ 168 (BSU) vs. _B. horneckiae_ DSM 23495\({}^{\text{T}}\) (BHO).  
Figure 2: FTIR spectra of spores from _B. horneckiae_ SBP3 (SBP3), _B. horneckiae_ DSM23495\({}^{\text{T}}\) (BHO) and _B. subtilis_ 168 (BSU).  
This analysis allowed us to distinguish each spore spectrum as a distinctive feature of each strain. The SBP3 spectrum was more similar to that of BHO (XWTC = 0.8771) (Figure 3B) than to that of BSU (XWTC = 0.8200) (Figure 3A). The affinity observed between the BHO and BSU spectra was slightly higher than that between SBP3 and BSU (XWTC = 0.8262) (Figure 3C).