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Dielectric Study of the Physical State of Electrolytes and Water Within Bacillus cereus Spores

¹ Department of Electrical Engineering, University of Rochester, Rochester, New York 14627
² Department of Microbiology, University of Rochester, Rochester, New York 14627
³ Department of Microbiology and Public Health, Michigan State University, East Lansing, Michigan 48823

ABSTRACT

Dielectric measurements revealed that dormant spores of Bacillus cereus have extremely low conductivities at high frequencies (50 MHz) and so must contain remarkably low concentrations of mobile ions both within the core and in the surrounding integuments. Activation, germination, and outgrowth were all accompanied by increases in conductivity of the cells and their suspending medium, and this result indicated that intracellular electrolytes had become ionized and leaked from the spores. High-frequency dielectric constants of spores were consistent with normal states for cell water. These values increased during successive stages of development from dormant spore to vegetative bacillus, and they could be directly related to increases in cell water content. In all, the results refuted a model of the dormant spore involving freely mobile, ionized electrolytes and supported a model involving electrostatically bound electrolytes.

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