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Killing of Bacillus Megaterium Spores by X-rays at the Phosphorus K-edgeThis study continues a progression of experiments on the radiation-induced killing of bacterial spores that began at the Argonne National Laboratory in 1957. A series of aliquots of Bacillus megaterium spores were prepared onto polycarbonate filters and irradiated with photons of 2159 eV compared to 2140 eV energy on the 2-IDB beamline at the Advanced Photon Source. Flux density was approximately 10(exp 18) photons/sec/sq mm. The phosphorous K-edge absorption spectrum in these spores was determined to peak at 2159 eV, wheras 2140 eV was determined to be outside that absorption spectrum. Spores on filters were irradiated at ambient conditions, and were either immediately plated for colony formation after irradiation, or were held for postirradiation exposure to oxygen prior to plating. Slopes of survival curves from the four conditions of irradiation, i.e., two photon energies each comparing immediate plating vs postirradiation holding, were used for quantitative determination of differences in rates of spore killing over a range of radiation doses. It was found that spores irradiated at the phosphorus K-edge were killed 20% more efficiently than when irradiated with 2140 eV photons, and this was true for both immediate plating and postirradiation holding in air. Postirradiation holding in air increased killing efficiency by about 12% for both photon energies compared to plating immediately after irradiation. The increase of killing efficiency with postirradiation holding is less than expected from earlier experiments using relatively low-flux X-rays, and raises the possibility of dose-mitigation by radical-radical recombination in the case of high-flux X-rays from the synchrotron.
Document ID
20010040764
Acquisition Source
Marshall Space Flight Center
Document Type
Conference Paper
Authors
Richmond, Robert C.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Frigo, Sean P.
(Argonne National Lab. IL United States)
Ehret, Charles F.
(General Chronobionics Clarendon Hills, IL United States)
Rose, M. Franklin
Date Acquired
August 20, 2013
Publication Date
January 1, 2001
Subject Category
Life Sciences (General)
Meeting Information
Meeting: 48th Radiation Research Society Meeting
Location: San Juan
Country: Puerto Rico
Start Date: April 22, 2001
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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