EXPERIMENT STATION REPORTS. U\) 



COMPARISON OF THE GROWTH OF DAIRY GERMS ON WHEY, 

 ORDINARY AND 4% LACTOSE AGAR. 



To check up the results obtained by plating the miscellaneous milk 

 organisms, pure cultures of dairy germs (taken from butter), were 

 grown on whey, ordinary and 4% lactose agar. 



Four per cent lactose agar was used in this experiment as it was 

 found to support the growth of the milk germs better than the ordinary 

 {!%) lactose agar, at 37° C. The explanation for this is that the media, 

 in the per cent of lactose, reaches more nearly the composition of milk. 



All media was made according to standard methods, and adjusted 

 to 15° acid. 



Each germ was plated in three series and special care was taken 

 to have like conditions for comparisons. 



METHOD. 



1. Agar streak cultures of each germ, 3 days old were used for 

 making transfers. 



2. The 3 day culture was transferred to a broth tube and grown 48 

 hours. 



3. A loop transfer from (2) was made into 50 cc. of broth and 

 grown 24 hours at 22° C. 



4. With a sterile pipette, 1 cc. of the 24 hour broth suspension was 

 transferred into a 99 cc. dilution flask. (.06% salt solution.) 



Dilutions 1-1,000, 1-10,000, 1-100,000, 1-1,000,000, and 1-10,000,000 

 were made. 



5. Each germ was plated on the different media from the last four 

 dilutions. 



6. Plates were kept 7 days at 22° C. and counts recorded. 



COMPARISON OF THE GROWTH OF DAIRY GERMS, ETC. 



The germs D-L, AS, VI c A, and IV c B, are of the lactic acid 

 type. The other germs, III b G, IV b D, III b C, VIII b E, and VIII 

 b A are associative germs in milk and other dairy products. 



The counts are recorded as number of germs per plate. 



