270 DIFCO MANUAL 



in a medium for culturing Agrobacterium tumejaciens in studying the specific 

 bacteriophage of this organism. Countless other references to the use of this 

 product are to be found in bacteriological literature. 



1 Standard Methods for the Examination of » j. Bact., 36:567:1938. 



Water and Sewage, 9th Edition: 1946. * J. Bact., 29:349: 1935. 



8 Standard Methods for the Examination of 5 J. Bact., 35:429: 1938. 



Dairy Products, 9th Edition: 1948. « Phytopathology, 27:871:1937. 



BAGTO-YEAST EXTRACT (B127) 



Bacto-Yeast Extract is the water soluble portion of autolyzed yeast. The 

 autolysis is carefully controlled to preserve the naturally occurring B-complex 

 vitamins. Bacto-Yeast Extract is prepared and standardized for bacteriological 

 use. It is an excellent stimulator of bacterial growth and is used in culture media 

 in place of, or as an adjuvant to, beef extract. In concentrations of 0.3-0.5 per 

 cent, as it is generally employed, it forms sparklingly clear solutions with a 

 reaction of pH 6.6. 



Bacto-Yeast Extract has been used advantageously in culture media for studies 

 of the bacteria in milk and other dairy products. Its usefulness for this purpose is 

 attested in such reports as those of Prickett^ on the thermophilic and thermoduric 

 bacteria of milk. Since publication of this work, Bacto-Yeast Extract has been 

 used with increasing frequency in the study of the bacterial flora of milk. Among 

 the references to its use for this purpose are those of Hucker and Hucker^ on the 

 number and type of bacteria in commercially prepared infant foods, Breed et al.^ 

 on methods for the examination of thermophiles in dry milk and Downs and his 

 associates* on methods for the study of these organisms in evaporated and con- 

 densed milk. Bowers and Hucker^ have also studied the effect of Bacto-Yeast 

 Extract in media employed for counting bacteria in milk. An increasing number 

 of references to Bacto-Yeast Extract is to be found in bacteriological literature. 

 Hutner^ used this product in a stock broth for the streptococci. Nelson and 

 Werkman''' have used Bacto-Yeast Extract as an ingredient of the medium they 

 employed for cultivation of Lactobacillus brevis. Werkman and his associ- 

 ^|-gs8,9,io,ii have used Bacto-Yeast Extract media for propagating organisms of 

 the propionic acid group. Partansky and McPherson^^ ^5^^ Bacto-Yeast Extract 

 in combination with Bacto-Malt Extract, and Bacto-agar for the growth of molds 

 in their laboratory method for testing the mold resistant properties of oil paints. 



Pringsheim and Robinow^^ in their studies on the cultivation of Caryophanon 

 latum reported very good growth of the organism in agar media containing 

 Bacto-Yeast Extract. Some batches of laboratory made autolysates of Bakers 

 yeast gave excellent results but others were unsatisfactory. They were able to 

 rely on a medium prepared with 0.5 per cent Bacto-Yeast Extract and 0.5 per 

 cent Bacto-Peptone, which was very favorable for isolation and maintenance of 

 the culture. In a survey of ingredients for a medium for the standard plate count 

 for dairy products, Buckbinder and associates^* compared various yeast extracts 

 and showed that media prepared with Bacto-Yeast Extract gave a higher count 

 than similar media prepared with other yeast extracts. 



Bacto-Yeast Extract is an excellent source of B-complex vitamins and is often 

 used to supply these factors in bacteriological culture media. For example, Snell 

 and Strongly used Bacto-Yeast Extract for the preparation of the yeast supple- 

 ment in their medium for riboflavin assay. It has proved to be a valuable ingredi- 

 ent of media used for carrying stock cultures and for preparation of inocula of 



