390 Modern Food Microbiology
Apparent Mechanisms of Resistance
Why these organisms are so resistant to radiation is unclear. The extreme resistance of deinococci
to desiccation has been observed and presumed to be related in some way to radioresistance. The
complicated cell envelope of these organisms may be a factor, but precise data are wanting. All are
highly pigmented and contain various carotenoids, a fact that suggests some relationship to radiation resistance. However, these pigments have been found to play no role in the resistance of D.
radiophilus.
38,44 Some of the chemical events that occur in organic matter after irradiation are outlined in Figure 15–4. The radiolysis of water leads to the formation of free radicals and peroxides, and
radiation-sensitive organisms appear to be unable to overcome their deleterious effects. Chemicals
Figure 15–4 Summary of radiation and postirradiation effects in organic matter. Source: From Bacq and
Alexander
5 reprinted with permission of the authors, Fundamentals of Radiobiology, copyright c
1961, Pergamon Press.