PHYSIOLOGICAL CLASSIFICATIONS 153 



10. Compute the weight of the bacteria in the flask of 

 distilled water at its highest count. 



What is the smallest amount that may be weighed on the 

 ordinary analytical balances? Conclusions? 



11. Plot curves to show whether bacteria are decreasing 

 or increasing. Offer a logical explanation for the direction 

 the curve takes in each instance. 



12. Note the conditions under which distilled water is 

 obtained and dispensed in the laboratory. Why is the 

 distilled water not sterile? 



13. By what process of distillation may distilled water be 

 obtained free from microorganisms? What several factors 

 outside of errors in technic may have influenced your 

 results? 



14. What would be the comparative influence of a large 

 and a small inoculation upon the number of B. coli surviv- 

 ing the 5 days sojourn in the distilled water? 



16. State your results in detail, draw any possible con- 

 clusions and point out any practical applications. 



REFERENCES 



MARSHALL, C. E.: Microbiology, pp. 88-89. 



FISCHER, ALFRED : Structure and Functions of Bacteria, pp. 52-54. 

 PRESCOTT and WINSLOW: Elements of Water Bacteriology, 3d Ed. 

 pp. 151-153. 



SOME PHYSIOLOGICAL CLASSIFICATIONS OF 

 BACTERIA 



Bacteria are often classified, in general terms, according 

 to their functions, into: 



Saprogenic, or putrefactive bacteria; 



Zymogenic, or fermentative bacteria; 



Pathogenic, or disease-producing bacteria. 

 According to their food requirements, into : 



Prototrophic, requiring no organic food (e.g., nitrifying 

 bacteria) j 



