426 



Scientific Proceedings (132) 



211 (2171) 



Effect of certain electrolytes on the buffering power of 

 bacterium coli. 1 



By I. S. FALK and H. J. SHAUGHNESSY. 



[From the Department of Public Health, Yale School of Medicine, 

 New Haven, Conn.] 



In the present studies we have developed a technique for the 

 measurement of the power of the bacterial cell to combine with 

 hydrogen and hydroxyl ions. The bacteria show a general ten- 

 dency to simulate amphoteric colloids and we have therefore 

 measured their amphoteric property by the use of titration 

 curves. A bacterial suspension in water or in a particular salt 

 solution is titrated electrometrically with hydrochloric acid and 

 with sodium hydroxide and similar titration curves are obtained 

 for the menstruum alone. From these two sets of curves it 

 is possible to calculate a series of "buffer ratios" by taking the 

 quotients of the amounts of acid or alkali added to shift the 

 P H one unit in the bacterial suspension and in the menstruum 

 alone. Such buffer ratios have been calculated for each P H unit 

 zone between P H 2 and P H 12. The titration cells which have 

 been developed for these experiments are illustrated in the ac- 

 company figure. The buffer ratios for Bact. coli in distilled 

 water, 0.725, M NaCl, 0.145 M CaCL and in 0.580 M NaCl + 

 0.145 M CaCl 2 solutions are presented in Table I. 



TABLE I. 



Average Buffer Ratios for Bacterium coli in Water and in Salt Solutions. 



P H Zone. 



Ratio for Bact. coli in: 





Water. 



0.725 M 

 NaCl 



0.145 M 

 CaCl 2 



0.580 M NaCl 4- 

 0.145 M CaCl 2 



3-2 



0.85 



1.5 



1.0 



1.2 



4-3 



0.77 



1.0 



1.0 



1.3 



5-4 



1.7 



1.8 



0.75 



1.4 



6-5 







1.0 



1.0 



7-6 



8.2 



1.9 





1.3 



7-8 



4.7 



1.4 







8-9 



1.7 



0.75 



1.2 



1.3 



9-10 



2.4 



0.88 



1.5 



0.75 



10-11 



0.59 



0.92 



0.92 



0.91 



11-12 



0.93 



0.68 



0.91 



1.0 



Number of 











experiments 



7 



3 



3 



4 



i Studies reported here were aided by a grant from the Loomis Research 

 Fund of the Yale School of Medicine. 



