DEHYDRATED CULTURE MEDIA 39 



BACTO 



FORMATE RICINOLEATE BROTH 



DEHYDRATED 



Bacto-Formate Ricinoleate Broth is used in the confirmed and completed tests 

 for the presence of members of the coliform group in water and sewage examina- 

 tion and for the detection (presumptive) test of members of the coliform group, 

 as given in the "Standard Methods for the Examination of Dairy Products," 

 Ninth Edition, page 131, 1948. Its use is confined to the study of the possible 

 presence of spore-forming lactose-fermenting organisms as given in "Standard 

 Methods for the Examination of Water and Sewage," Ninth Edition, 1946, pages 

 196 and 197. This selective broth may also be used in parallel planting with 

 Lactose Broth in the control of water filtration plant operations as described in 

 Appendix I of the Ninth Edition, page 226. A complete discussion of this me- 

 dium is given on page 60. 



BACTO 



LAURYL TRYPTOSE BROTH (B241) 



DEHYDRATED 



Bacto-Tryptose 20 g. 



Bacto-Lactose 5 g. 



Dipotassium Phosphate 2.75 g. 



Monopotassium Phosphate 2.75 g. 



Sodium Chloride 5 g. 



Sodium Lauryl Sulfate 0.1 g. 



Bacto-Lauryl Tryptose Broth is prepared according to the formula of Mallmann 

 and Darby^ and is recommended for use in the standard tests for the coliform 

 group as specified in "Standard Methods for the Examination of Water and 

 Sewage"-. 



The fermentation of lactose with the production of gas has been used as an 

 indicator of the potability of water for many years. The formation of gas from 

 Lactose Broth constitutes a presumptive test for the coliform group (this terra 

 includes all aerobic and facultative anaerobic Gram-negative non-spore-forming 

 bacilli which are capable of producing gas from lactose)-. Cowls^ showed that 

 the addition of sodium lauryl sulfate to Lactose Broth gave a medium selective 

 for the coliform group. Darby and Mallmann* demonstrated the value of Bacto- 

 Tryptose in the detection of coliform organisms. In a 2 per cent concentration 

 of Bacto-Tryptose the rate of reproduction during the early logarithmic growth 

 phase was increased over that obtained with Bacto-Peptone. The addition of 

 phosphate buffer to the Bacto-Tryptose medium caused a greater growth in the 

 late logarithmic phase and slightly greater increase during the lag phase than 

 did the non-buffered medium. When sodium chloride was added to the medium 

 a marked increase in the rate of reproduction during the lag and early growth 

 phases was observed. Their final medium permitted the so-called "slow lactose 

 fermenters" to produce gas in greater quantities in a shorter period of time. The 

 medium consisted of 2 per cent Bacto-Tryptose, 0.5 per cent lactose, 0.4 per cent 

 dipotassium phosphate, 0.15 per cent monopotassium phosphate, and 0.5 per cent 

 sodium chloride, and had a final reaction of pH 6.8. 



In an attempt to improve the methods used to demonstrate members of the 

 coliform group from water, Mallmann and Darby^ investigated a large number 

 of wetting agents, and showed that sodium lauryl sulfate gave best results as a 



