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Over the years, Clostridium botulinum has been separated into four groups (I IV), depending on how proteolytic the strains are as well as other physiological traits.  The term proteolytic refers to the ability of the strains to hydrolyze proteins, such as egg albumem or casein.  These difference within the species, signifies adaptations made by the organism, depending on its location.  The table on the Classification page shows the differences between these groups. But proteolytic research is not the only type of research done on C. botulinum adaption.  There have also been studies on three particular resistances that spores possess heat resistance, radiation resistance, and resistance to other agents.


                    Heat Resistance                     


Generally, with food processing, heat is a key element to preservation and the destruction of bacteria.  Since C. Botulinum does quite enjoy the lovely habitat that improperly preserved foods provide, resistances in types A, B, and E have developed.  In particularly, group I (strains A and B in this case), resistance to temperature is high.  Spores in these strains can survive in temperatures in the upwards of 120 degrees Fahrenheit.  This resistance to heat is largely attributed to the temperature at which the cultures are grown.

                   Radiation Resistance             


The concept of using radiation to eliminate potential dangerous bacteria is a double-edged sword.  With too much radiation, the bacteria are indeed eliminated, but the food itself changes so much it tastes terrible.  With too little, weak bacteria are destroyed, but stronger ones, such as C. botulinum have free reign.


?       Resistance to Other Agents        ?


There are a number of other resistances that different types of C. botulinum possess.  One example would be the resistances to detergent-chlorine complexes and iodophor compared to those in regular chlorine.  In this instance, the resistance for the impure chlorine were much higher than those in regular chlorine (the chemicals still killed the bacteria it just took longer).  Another example would be the resistance that C. botulinum spores have to ultraviolet light.  For an unknown reason, all strains tend to possess some sort of protection against harmful ultraviolet rays.


These resistances make C. botulinum one tough organism, but how does it reproduce?  Check it out on the Life History page.


Pictures on this page courtesy of Microsoft Clip Art.


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 Author - Phil Strandwitz (

Published April 17th, 2008