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THE KILLING OF CERTAIN BACTERIA BY X-RAYS
1Laboratories of The Rockefeller Institute for Medical Research.
The Journal of Experimental Medicine
|October 30, 2009
Summary
X-rays kill bacteria like Escherichia coli (B. coli) and Salmonella aertrycke (B. aertrycke) exponentially. A single X-ray quantum absorption event causes bacterial death, with only a fraction of absorbed quanta being lethal.
Area of Science:
- Microbiology
- Radiation Biology
- Biophysics
Background:
- Bacterial susceptibility to radiation is a critical area of study for understanding sterilization and radiation effects.
- Previous research has explored the impact of various radiation types on microbial life, but the precise mechanism of X-ray induced bacterial death requires further elucidation.
Purpose of the Study:
- To investigate the lethal effects of copper K X-rays and tungsten tube radiation on Escherichia coli (B. coli) and Salmonella aertrycke (B. aertrycke).
- To determine the relationship between absorbed X-ray energy quanta and bacterial survival.
- To estimate the volume of sensitive cellular components responsible for radiation-induced death.
Main Methods:
- Exposure of B. coli and B. aertrycke cultures to copper K X-rays and soft general radiation from a tungsten X-ray tube (12 KV).
- Measurement of air ionization to quantify absorbed X-ray energy.
- Calculation of average quanta absorbed per bacterium per second (alpha).
- Mathematical modeling of bacterial survival ratios based on absorbed quanta.
Main Results:
- Both radiation types demonstrated a linearly exponential killing effect on B. coli and B. aertrycke.
- The two bacterial species exhibited similar sensitivity to the tested radiations.
- Bacterial death was correlated with the absorption of single X-ray quanta.
- Approximately 1 in 20 absorbed quanta resulted in bacterial death.
Conclusions:
- The study supports a single-hit mechanism where the absorption of one X-ray quantum can lead to bacterial death.
- The sensitive cellular targets responsible for lethality constitute a small fraction (less than 0.06) of the total bacterial volume.
- These findings provide insights into the biophysical mechanisms underlying X-ray inactivation of bacteria.
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