VOL. 12 (1953) . BIOCHIMICA ET BIOPHYSICA ACTA 4I 



GROWTH AND PHAGE PR(3DUCTI0N OF B. MEGATHERIUM 



i\. KINETICS OF CELL GROWTH, PHAGE PRODUCTION, AND PROTEIN 

 AND NUCLEIC ACID SYNTHESIS IN LYSOGENIC MEGA THERIUM CULTURES 



by 



JOHN H. NORTHROP 

 (with the technical assistance of MARIE KING) 



The Laboratory of the Rockefeller Institute for Medical Research, Department of Bacteriology, 



University of California, Berkeley (U.S.A.) 



Krueger and Northrop found that the increase in phage in the presence of a 

 susceptible organism followed a logarithmic curve just as does the increase in the cell 

 concentration of the suspension. That is, 



— = hj,F and — - = A„o 



dt ^ dt ^ 



Kp = growth rate (constant) of phage 

 Therefore, Kg = growth rate (constant) of cells 



dP _dB Kp (2)* 



In these experiments, the amount of phage added was small compared to the number 

 of cells. The increase in the amount of phage occurs in the cells and each infected cell 

 liberates several phage particles. The reaction, therefore, is exactly the same in general 

 as that of the multiplication of the cells, except that one infected cell forms many phage 

 particles, but one normal cell forms only two cells. It is to be expected, therefore, that 

 the reactions will follow the same course, but with different rates. In both cases the 

 growth constant (fractional rate of increase per unit of time) is independent of the 

 concentration. This is true whether the concentration increase during the course of the 

 reaction, or whether it is increased by adding more P ox B from an outside source. In 

 either case the results agree with the logarithmic equation. 



It has recently been found (Northrop^) that the same relation between phage 

 production and bacterial growth holds in the case of sensitive B. megatherium + C phage 

 when all the cells are infected at the beginning of the experiment. In this system, a 

 dilute cell suspension continues to grow for 2-3 cell divisions after infection and before 

 lysis occurs. The number of phage particles liberated per original infected cell at the end 

 of the reaction is predicted by equation (2). (In the case of resting cells, the increase in 

 RNA must be used instead of the increase in cells.) Under these conditions the multipli- 



This is the same equation as that^found empirically by Huxley -^' -* to represent the relationship 

 between the size of various organs in growing animals or plants. (Any pair of value each of which varies 

 logarithmically with t, must be related by equation (2); the reverse statement, however, is not true. 

 Values of P and B which satisfy equation (2) do not necessarily have any simple relation to the time). 



References p. 50. 



