V. THE KINETICS OF GROWTH 

 OF MICROORGANISMS 



BY C. B. VAN NIEL^ 



THE consensus of opinion, expressed in the preceding chapters, 

 seems to have been that "growth is a very complex phenome- 

 non." I see no reason for amending this verdict when consider- 

 ing the growth of microorganisms. It is true that these creatures appear, 

 even when studied with the best optical or electronic equipment, as 

 rather simple structures; and, compared with higher plants and animals, 

 they certainly do not seem to be as highly differentiated. Nevertheless, 

 they display an astonishing diversity of functions which in many re- 

 spects they share with the trees, oysters, butterflies, and elephants. 



Generally they are found swimming or floating about in an environ- 

 ment containing a more or less abundant variety of chemical compounds. 

 From these they pick up or absorb special ones which as a result of 

 metabolic activities are subsequently converted into cellular constituents. 

 When a large enough quantity and variety of the latter have been pro- 

 duced, and when the individual organism has sufficiently increased in 

 size, it divides into halves, each one of which then repeats the process. 

 This continues until the food supply, or specific ingredients thereof, 

 gives out, or until inhibitory metabolic products begin to interfere with 

 normal development. 



The amazing feature of growth, in a microbial culture as in living be- 

 ings in general, lies in the fact that it involves the manufacture and or- 

 derly arrangement of the manifold structural and functional components 

 which characterize the organism in such a way as to duplicate accurately 

 an existing pattern. How this is accomplished is one of the major bio- 

 logical problems, fundamentally as complex in the lower as in the higher 

 forms of life. On the other hand, the comparative ease of handling 

 microorganisms, their rapid growth, and the opportunity for rigorously 

 controlling various environmental factors all combine to render them 

 favorable material for experimental studies of the basic mechanism of 

 the growth process. 



In several instances the successful resolution of a complex phenome- 

 non into its constituent components, the latter more readily amenable to 

 scientific analysis than the overall event, has resulted from kinetic 



1 Hopkins Marine Station of Stanford University, Pacific Grove, Calif. 



