CHAPTER 7 



Bacterial Multiplication 



GROWTH CURVES 



METHODS FOR DETERMINING TOTAL BACTERIAL NUMBERS 



Breed smears 



Wright's proportional count technic 



Hemocytometer method 



Opacity method 



Centrifuge method 



TECHNICS FOR DETERMINING VIABLE BACTERIAL COUNTS 

 Broth dilution method 

 The plate count 



GROWTH CURVES 



The speed with which a microorganism will multiply under a 

 standard set of conditions is predictable, but minor variations in 

 any factor affecting growth of organisms will alter the growth rate. 

 Such considerations as the concentration and availability of food, 

 pH, temperature, moisture, presence of accessory growth-stimulat- 

 ing substances, surface tension, and the accumulation of waste 

 products have a direct bearing on growth curves. 



Growth of higher forms of plant and animal life involves an 

 increase in size which accompanies an increase in the number of 

 cells comprising a given tissue or structure of the body. Bacterial 

 growth, on the other hand, is usually used as a synonym for multi- 

 plication. Bacteria grow to a predetermined size and stop if 



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