The Dielectric Structure, Free Water Content, and Dipicolinic Acid Distribution within Viable Bacterial Spores.
SCIENCE SPECTRUM INC SANTA BARBARA CALIF
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The differential light scattering characteristics of single spores from Bacillus sphaericus and Clostridium filamentosum were measured and recorded for several hundred different spores using an argon-ion laser source lambda 514.5 nm and a special single particle light scattering photometer. Typical recorded light scattering patterns were interpreted analytically by adjusting the parameters of a spherically symmetric model to the data using a least squares fitting procedure. For both species, the average refractive index of the spore cortex was 1.54 plus or minus 0.01, while the average cost refractive index was only 1.47 plus or minus 0.01. The size fluctuations of the cortices were very small and suggest that the cortex structure may well be identical for different spores of the same species. The free water content of spores was found to be negligible since measurements of individual spores suspended in a dry environment for 24 hours showed no changes in time. Spores for which dipicolinic acid had been removed could not be used to obtain satisfactory light scattering patterns for subsequent analyses. A hypothesis is presented that DPA acts as a filler material in the cortex to prevent free water penetration. Author