Comparison of quasielastic light scattering and laser diffractometry as nondestructive probes into the structure of Bacillus sphaericus spores produced at different temperatures

Abstract

Quasielastic light scattering (QLS) and laser diffractometry (LD) are relatively novel nondestructive procedures for estimating the sizes of bacterial spores in suspension. This study for the first time directly compared the two with a destructive procedure, namely, scanning electron microscopy (SEM), for quasispherical spores of Bacillus sphaericus. Because of the different physical aspect measured, the sizes derived by QLS and LD are, as could be expected for spores with an exosporium, significantly different. The larger estimates obtained by QLS (1.70, 1.58, and 1.14 μm for spores produced at 15°C [BS15], 20°C [BS20], and 30°C [BS30], respectively) than by LD (0.56 [BS15], 0.58 [BS20], and 0.52 [BS30] μm) and SEM (0.64 [BS15], 0.58 [BS20], and 0.70 [BS30] μm) are explained in terms of the detection by QLS, LD, and SEM of different spore layers and the degree of nonsphericity of the latter.