242 



Journal of Agricultural Research voi.xiii,no.4 



Streptococcus X was found to be abundant in Cheddar and Roquefort 

 cheese. Thirteen representative strains were selected for detailed study. 

 Four of them were from Cheddar, and nine were from imported and 

 experimental Roquefort cheese. In Table II, where the data for this 

 group are summarized, the strains numbered 2 were from Cheddar 

 cheese, and those numbered 96 were from Roquefort cheese. 



Table II. — Characteristics of Streptococcus X 



'■ The minus sign (— ) indicates failure to form acids. 



b Not curdled in 14 days. 



Streptococcus X requires a longer time than S. lacticus to curdle litmus 

 milk. Table II shows that the cultures varied in that respect from 2 to 

 1 2 days. There is a partial reduction, or no reduction of the litmus. In 

 peptone milk curdling usually takes place in one day. There is no 

 crystal formation in milk cultures. 



The most striking differentiation between S. lacticus and Streptococcus 

 X is the large quantity of acetic acid formed in milk cultures by the 

 latter. The quantity of acetic acid produced in m.ilk cultures was deter- 

 mined for 10 strains of this group. With the exception of one culture, 

 2ac, which produced 49.39 c. c. N/jo acetic acid in 500 c. c. of milk, 

 w^hich was somewhat less than was characteristic for the group, the 

 quantity was fairly constant, varying in eight cultures between 57.88 

 and 67.75 c. c. Culture 2ac produced 70 c. c, slightly more than the 

 characteristic quantity of acetic acid. If calculated for i liter of milk, the 

 characteristic quantity of acetic acid produced by this group of strep- 

 tococci is equivalent to 0.7 to 0.8 gm. per liter, or approximately six 

 times the quantity of acetic acid produced by S. lacticus. 



The reduction of the hydrogen-ion concentration in peptone-yeast 

 broth with an initial concentration of Ph = 6.0 was precisely the same for 

 Streptococcus X as for 5. lacticus. Two of the thirteen cultures varied 

 slightly from the characteristic final Ph = 6.8. 



