178 GENERAL MICROBIOLOGY 



stopper, replace the stopper with a sterile cotton plug and 

 note both cultures after twenty-four hours. What occurs 

 in either case? 



6. Which is the better temperature for the growth of 

 this organism? Can you suggest a reason why? What 

 is the natural habitat of this type of organism? Of what 

 importance are they? 



What would you conclude regarding the respiration of 

 phosphorescent bacteria? What term is applied to bacteria 

 exhibiting this phenomenon? Of what importance is this 

 phenomenon? 



7. State your results in full, and draw any conclusions. 

 What practical application of the above may be made? 



REFERENCES 



LAFAR: Technical Mycology, Vol. I, pp. 123-126. 



MARSHALL: Microbiology, (1911), p. 129 



FISCHER, A.: Structure and Functions of Bacteria (1900), pp. 63-64. 



ENZYMES: CLASSIFICATIONS AND REACTIONS 



Enzymes can be classified in several different ways : 



I. According to their place of activity as endo-enzymes 

 (intracellular) or exo-enzymes (extracellular) ; 



II. According to the type of food substance acted upon, 

 as proteolytic (protein-digesting), lipolytic (fat-digesting), 

 enzymes attacking carbohydrates, etc.; 



III. The most satisfactory and inclusive classification 

 is that denoting the chemical reactions produced by 

 the enzyme during its activity. Enzymes may thus be 

 called : 



1. Hydrolytic, the addition of one of more molecules of 

 water to the molecule of the substance acted upon. 



2. Enzymes producing intramolecular changes, i.e., caus- 

 ing a rearrangement of the atoms within the molecule. In a 

 few cases these changes may be hydrolytic (urease) but a 



