Tuesday, 24 May 2005

This presentation is part of: Graduate Posters

Study of pH-response of Bacillus subtilis spores

Elizabeth M. Bonvouloir, Pace University, New York, NY and Sergey V. Kazakov, Pace University, Pleasantville, NY.

An approach to study electrochemical behavior of bacterial spores is proposed and tested by measuring pH in the exterior to Bacillus subtilis spores. The approach is based on the statement that properties of an ionic reservoir can effect on the properties of the external solution and can change the concentration of ions in the exterior to spores. The structure of Bacillus spores, particularly, the properties of the spore cortex, a peptidoglycan cross-linked polymer (negative net charge, high level of mobile ions, high degree of freedom of ions movement, ability to change volume in response to ionic changes or water content), allow one to consider a spore as a natural ionic reservoir. The objective of the present work is to examine the ability of Bacillus subtilis spores to accumulate and release ions and to expand or contract in response to external conditions. The potentiometric titration curves for Bacillus subtilis spores were obtained to show that each spore behaves like almost infinite ionic reservoir capable of accumulating billions of protons. The parameters of protonation/deprotonation kinetics were extracted from the time-resolved measurements of establishing an equilibrium pH in spores' suspensions carried out at different conditions effecting on spore germination (extreme pH, temperature, and nutrients). The spore size and shape were monitored using dynamic light scattering and phase contrast optical microscopy. Electrochemical properties of bacterial spores are of great potential for new methods of spore detection and identification and for understanding the phenomenological and molecular mechanisms of germination and sporulation of the Bacillus bacteria.

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