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International Journal of Microbiology
Volume 2012, Article ID 579593, 9 pages
Research Article

Electron Beam Irradiation Dose Dependently Damages the Bacillus Spore Coat and Spore Membrane

1Department of Biological Sciences, Kent State University, Kent, OH 44242, USA
2College of Technology, Kent State University, Kent, OH 44242, USA
3College of Public Health, Kent State University, Kent, OH 44242, USA

Received 12 August 2011; Revised 13 October 2011; Accepted 14 October 2011

Academic Editor: David C. Straus

Copyright © 2012 S. E. Fiester et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Effective control of spore-forming bacilli begs suitable physical or chemical methods. While many spore inactivation techniques have been proven effective, electron beam (EB) irradiation has been frequently chosen to eradicate Bacillus spores. Despite its widespread use, there are limited data evaluating the effects of EB irradiation on Bacillus spores. To study this, B. atrophaeus spores were purified, suspended in sterile, distilled water, and irradiated with EB (up to 20 kGy). Irradiated spores were found (1) to contain structural damage as observed by electron microscopy, (2) to have spilled cytoplasmic contents as measured by spectroscopy, (3) to have reduced membrane integrity as determined by fluorescence cytometry, and (4) to have fragmented genomic DNA as measured by gel electrophoresis, all in a dose-dependent manner. Additionally, cytometry data reveal decreased spore size, increased surface alterations, and increased uptake of propidium iodide, with increasing EB dose, suggesting spore coat alterations with membrane damage, prior to loss of spore viability. The present study suggests that EB irradiation of spores in water results in substantial structural damage of the spore coat and inner membrane, and that, along with DNA fragmentation, results in dose-dependent spore inactivation.