INGREDIENTS OF CULTURE MEDIA 261 



A complete discussion of the methods for the determination of indole is given 

 under Bacto-Tryptone on page 53. 



Investigation of the usefulness of Bacto-Tryptone in other fields has demon- 

 strated a number of industrial applications. The National Canners Association, 

 in its "Bacterial Standards for Sugar,"^ specified the use of Tryptone media for 

 the detection of the organisms causing "flat sour" spoilage of canned goods and 

 also for detecting the presence of "sulfide spoilage" organisms in sugar.^ 



In his studies of the thermophilic bacteria of milk, Prickett^ developed a 

 medium containing Bacto-Tryptone which possessed excellent growth-stimulating 

 properties for these organisms. Bowers and Hucker^ also demonstrated the advan- 

 tages of culture media containing this peptone for propagating bacteria from 

 milk. An extensive survey of the use of the Bowers and Hucker medium for plate 

 counts of milk has been summarized by Yale.^*^ A modification of this medium, 

 still utilizing Bacto-Tryptone as the peptone, was originally recommended in 

 "Standard Methods for the Examination of Dairy Products,"^^ Seventh Edition, 

 1939, of the American Public Health Association for standard plate counts of 

 milk. The report of Abele^- analyzes in detail the results of extensive comparative 

 studies made with Tryptone Glucose Extract Milk Agar, and the former standard 

 Nutrient Agar. The use of the Tryptone medium has been continued since its 

 original introduction as a medium for the plate count of milk, and is specified in 

 the current Ninth Edition of "Standard Methods for the Examination of Dairy 

 Products."^^ The usefulness of Bacto-Tryptone as an ingredient of culture media 

 for the examination of milk is further shown by its use in the medium for the 

 total bacterial plate count of certified milk^* in which medium it may be em- 

 ployed alone or in conjunction with Proteose Peptone. 



Among the many other uses for Bacto-Tryptone that may be mentioned, Mc- 

 Clungi° in a study of anaerobic bacteria utilized a 1 per cent solution of Tryptone 

 as a basal medium for studying the physiological characteristics of Clostridia. 

 These organisms grew sparsely in the medium containing only Tryptone, but 

 developed rapidly in the presence of a utilizable source of carbon. Thus profuse 

 growth and also increase in hydrogen ion concentration served as criteria for the 

 utilization and fermentation of the test compound by these organisms. Spray^^ 

 utilized Tryptone for the propagation of anaerobes and McCoy^^ prepared the 

 antigens for her serological studies of the Clostridia in a 1 per cent Tryptone 

 Medium containing 0.5 per cent dextrose. Bowers and West^^ used Tryptone in 

 their studies on the streptococci and pneumococci and Moberly^^ employed this 

 peptone for the cultivation of Lactobacillus acidophilus. Pringsheim and Pring- 

 sheim^^ reported that Bacto-Tryptone renders the growth of Porphyridium 

 cruentum more vigorous and lasting. The best liquid medium for the growth of 

 this organism is sea water plus one half volume of Beijerinck solution with 0.2 

 per cent added Bacto-Tryptone. In 3-4 weeks a dense red mucilaginous growth is 

 formed. 



A typical quantitative analysis of Bacto-Tryptone is given on page 265. 



1 Am. J. Pub. Health, 11:834:1921. "^ Standard Methods for the Examination of 



2 J. Bact., 25:623:1933. Dairy Products, 7th Edition : 21 : 1939. 

 ' Pure Culture Study of Bacteria, 5: No. 3:1947. ^ Am. J. Pub. Health, 29:821:1939. 



* Centr. Bakt., I Abt., 76:1:1915. "Standard Methods for the Examination of 

 8 Standard Methods for the Examination of Dairy Products, 9th Edition: 93: 1948. 



Water and Sewage, 9th Edition: 230: 1946. ^* Methods and Standards for the Production of 



• Bacterial Standards for Sugar, 1935. Certified Milk, 1 953-54- 

 ''J. Assoc. Official Agr. Chem., 21:457:1938. ^^ J. Bact., 29:189:1935. 

 «Tech. Bull., 147, N. Y. State Agr. Exp. Sta., i« J. Bact., 32:135:1935. 



1928. " J. Bact., 34:321:1937. 



»Tech. Bull., 228, N. Y. State Agr. Exp. Sta., is Am. J. Pub. Health, 26:880:1036. 



1935- 19 Zentr. Bakt., II Abt. Orig., 96:329:1937. 



10 Am. J. Pub. Health, 28:148:1938. 80 j. Ecology, 37:57:1949. 



