CHAPTER 8 



Effects of Physical Forces on Bacteria 



TEMPERATURE RADIATIONS 



MOISTURE ULTRASOUND 



PRESSURE SURFACE TENSION 



ROCKING AND SHAKING 



Bacteria are composed of protoplasm, a living substance existing 

 in a rather delicate state of balance. Methods designed to destroy 

 organisms are aimed at tipping this protoplasm out of balance, 

 either by physical or by chemical forces. Once this unbalance has 

 been accomplished, a vital link in the chain of living events is 

 removed and normal metabolism of the cell is prevented. If the 

 tilt is severe enough and if it is prolonged, the cell will die. 



Without going into a great deal of detail relative to theories 

 proposed to explain how physical forces adversely affect bacteria, 

 this chapter will attempt to describe some of the commonlv used 

 physical technics. For students who mav be interested in further 

 readings on this topic, Porter's Bacterial Chemistnj and Flufsiologij 

 is recommended. Additional references covering reviews of spe- 

 cific phases of physical forces on bacteria may also be found in this 

 book. 

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