SALT EFFECTS IN BACTERIAL GROWTH 519 



the differences in the rate of growth are greatly increased. In 

 other words the H-ion range for optimum growth is widened or 

 narrowed as shown in the table given. 



This factor becomes of practical value in adjusting media 

 for optimum bacterial growth. The figures show that certain 

 ions are of value in pepton media for accelerating the growth 

 of Bad. coll and also for widening the range for optimum growth, 

 while certain other ions narrow the H-ion range and decrease 

 the rate of growth. This would perhaps explain the findings 

 of Cohen and Clark (1919) that culture media adjusted with 

 HCl had a higher limit of growth on the acid side than media 

 adjusted with acetic acid. 



SUMMARY. 



It has been shown that the growth of Bad. coli in 1 per cent 

 pepton medium is accelerated or retarded by different salts in 

 low molecular concentrations. 



The salt effects at various H-ion concentrations vary greatly. 

 Those salts which accelerate growth seem to widen the H-ion 

 range for optimum growth, while those which retard growth 

 seem to narrow the limits for optimum activity. 



Cations and anions are both effective. 



REFERENCES 



Bechhold, H., and Ziegler, J. 1919 In Colloids in biology and medicine, 



by H. Bechhold and J. G. M. Bullowa, p. 55. 

 Brooks, M. M. 1919 Jour. Gen Physiol., 2, 5. 

 Cohen, B., and Clark, W. M. 1919 Jour. Bact., 4, 409. 

 Greaves, J. E. 1916 Soil Science, 2, 443. 

 GusTAFSON, F. G. 1919 Jour. Gen. Physiol., 2, 17. 

 LoEB, J. 1918-1921 Jour. Gen. Physiol., 1918-19, 1, 39, 237, 363, 483, 559; 1919- 



20, 2, 87, 273; 1920-21, 3, 85, 247, 391. 

 Mathews, A. P. 1906 Jour. Infect. Dis., 3, 572. 

 WiNSLow, C.-E. A., AND Falk, I. S. 1919 Abs. Bact., 3, 5. 



