# Morphological Study of _Bacillus thuringiensis_ Crystals and Spores
## 3 Results
### B. thuringiensis Spore Morphology and Size Distribution
As for the anti-lepidopteran strains, a significant difference was also detected (\(p=0\)). HSD test showed no significant difference between the aspect ratios of LIPMKA and BLB1, \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multicolumn{10}{c}{**Spores**} \\ \hline \hline
**Strain** & **N** & \multicolumn{3}{c}{**Length (\(\upmu\)m)**} & \multicolumn{3}{c}{**Width (\(\upmu\)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** & 44 & 1.343 & 0.092 & 0.824–2.203 & 0.789 & 0.050 & 0.459–1.326 & 0.476 & 0.104 & 0.595 & 0.030 \\
**LIPMKA** & 365 & 1.649 & 0.023 & 0.870–2.767 & 0.8269 & 0.009 & 0.445–1.112 & 0.603 & 0.018 & 0.508 & 0.008 \\
**BLB1** & 212 & 1.459 & 0.053 & 0.395–2.259 & 0.722 & 0.025 & 0.221–1.069 & 0.465 & 0.032 & 0.501 & 0.009 \\
**AM65-52** & 118 & 1.257 & 0.04 & 0.706–1.928 & 0.783 & 0.026 & 0.465–1.142 & 0.426 & 0.036 & 0.636 & 0.026 \\
**AR23** & 823 & 1.503 & 0.014 & 0.673–2.118 & 0.863 & 0.0113 & 0.605–1.884 & 0.584 & 0.012 & 0.605 & 0.014 \\
**BUPM98** & 263 & 1.55 & 0.019 & 1.123–1.957 & 0.8093 & 0.009 & 0.598–1.054 & 0.540 & 0.015 & 0.525 & 0.007 \\
**H3** & 212 & 1.387 & 0.042 & 0.676–2.520 & 0.921 & 0.043 & 0.402–1.463 & 0.620 & 0.049 & 0.754 & 0.072 \\ \hline \hline \end{tabular}  
* Volumes were calculated assuming that spores are ellipsoids with volume \(V\) given by: \(V=\upmu\)_LW\({}^{2}/6\)_, where \(L\) represents the length and \(W\) the width of the spore.  
\end{table} 
Table 4: Morphological data of spores produced by the seven chosen _Bacillus thuringiensis_ strains for \(N\) measurements. Figure 10: Mean values of (**a**) spores aspect ratio and (**b**) volume of spores for the seven strains of _B. thuringiensis._ Error bars are uncertainties computed while taking into account the standard deviation for \(N\) measurements. meaning that they form spores with identical shapes. However, the spores synthesized by the reference _kurstaki_ strain HD1 are more spherical since they are significantly different from those of the two other _kurstaki_ strains. Concerning the spore volumes, two remarks are noteworthy. First, the reference _B. thuringiensis_ var. _kurstaki_ strain HD1 and BLB1 strain produce spores with much smaller volumes than their fellow _kurstaki_ strain LIPMKA, with average volumes of 0.476 \(\pm\) 0.104, 0.465 \(\pm\) 0.032 and 0.603 \(\pm\) 0.018 \(\upmu\)m\({}^{3}\) respectively. Indeed, a significant statistical difference (\(p=0\)) was highlighted and the HSD test distinguished the volume of the LIPMKA strain from those of the two other _kurstaki_ strains. Second, for the strains synthesizing spherical crystals (\(p=0\)), the reference strain AM65-52 produced the less voluminous spores with an average volume of 0.426 \(\pm\) 0.036 \(\upmu\)m\({}^{3}\), compared to more voluminous spores produced by BUPM98, AR23 and H3, with average volumes of 0.540 \(\pm\) 0.015, 0.584 \(\pm\) 0.012 and 0.620 \(\pm\) 0.049 \(\upmu\)m\({}^{3}\), respectively. In this case, the null hypothesis was rejected (\(p=0\)), and the HSD test showed a difference in the statistical data between the spore volume of AM65-52 and the other _israelensis_ strains, whereas no difference was revealed between AR23 and BUPM98. Furthermore, HSD test exhibited a significant difference between AM65-52 and H3.