# Morphological Study of _Bacillus thuringiensis_ Crystals and Spores
## 3 Results
### Anti-Dipteran Strains: Spherical Crystals by Israelensis and Kin  
The three _israelensis_ strains, AM65-52, AR23 and BUPM98, and H3, a novel non-_israelensis_ anti-dipteran strain belonging to a different phylogenetic group, produce spherical crystals. Histograms in Figures 5-8 represent the size distributions of the crystal radius, calculated as shown in Figure 1c. ANOVA univariate analysis showed significant differences between the strains (\(p\) = 0). Multi-comparison HSD tests indicated significant differences among the four strains. The sphere radius increased from the lowest value of 0.370 \(\pm\) 0.003 \(\upmu\)m for the Tunisian BUPM98 strain, to 0.381 \(\pm\) 0.003 \(\upmu\)m for the Lebanese AR23 strain and 0.394 \(\pm\) 0.009 \(\upmu\)m for the reference _B. thuringiensis_ var. _israelensis_ strain AM65-52; and reached the highest value of 0.411 \(\pm\) 0.003 \(\upmu\)m for the Lebanese non-_israelensis_ strain H3.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & & \multicolumn{8}{c}{**(a)**} \\ \hline  & & \multicolumn{8}{c}{**Bipyramidal Crystals**} \\ \hline
**Strain** & \(N\) & **Bipyramidal Height (2 h) (\(\upmu\)m)** & \multicolumn{3}{c}{**Side of the Base (\(\upmu\)m)**} & \multicolumn{3}{c}{**Volume * (\(\upmu\)m\({}^{3}\))**} & \multicolumn{3}{c}{**Aspect ratio**} \\ \hline  & & Average & Unc. & Range & Average & Unc. & Range & Average & Unc. & Average & Unc. \\ \hline HD1 & 1198 & 1.508 & 0.009 & 0.766–2.267 & 0.611 & 0.096 & 0.433–0.898 & 0.188 & 0.002 & 0.416 & 0.006 \\ LIPMKA & 1335 & 1.549 & 0.016 & 0.597–2.930 & 0.554 & 0.119 & 0.305–0.782 & 0.158 & 0.002 & 0.371 & 0.004 \\ BLB1 & 1400 & 1.531 & 0.014 & 0.723–2.685 & 0.582 & 0.116 & 0.369–0.993 & 0.173 & 0.002 & 0.393 & 0.004 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Morphological data of the crystals of the three _B. thuringiensis_ var. _kurstaki_ (a) bipyramidal and (b) cubic crystals for \(N\) measurements.  
Figure 5: **(a)** SEM image of the AM65-52 purified crystals. (**b**) Graph representing the radius size distribution in terms of frequency and cumulative percentage for the spherical crystals.  
Figure 6: **(a)** SEM image of the AR23 purified crystals. (**b**) Graph representing the radius size distribution in terms of frequency and cumulative percentage for the spherical crystals.  
Figure 7: **(a)** SEM image of the BUPM98 purified crystals. (**b**) Graph representing the radius size distribution in terms of frequency and cumulative percentage for the spherical crystals.  
The crystal components of the _israelensis_ strains are highly different than that of H3, with H3 having a peculiar set of crystal proteins (Table 1).  
The morphological data of the spherical crystals and their volumes are summarized in Table 3.  
ANOVA univariate analysis (\(p=0\)) followed by HSD test revealed a small, and yet statistically significant variation among spherical crystal volumes. Crystals of _B. thuringiensis_ var. _israelensis_ strain AM65-52 showed the largest volume of 0.283 \(\pm\) 0.021 \(\upmu\)m\({}^{3}\). Furthermore, the crystal volume of the non-_israelensis_ strain H3 was significantly larger than those synthesized by the _israelensis_ strains AR23 and BUPM98, as indicated by the HSD tests.