Morris Rockenmacher, Howard A. James, Sanford S. Elberg
1952 Journal of Bacteriology  
The chemically defined culture media for Pasteurella pestis which were formulated by Rao (1939, 1940a, b), Berkman (1942) , Doudoroff (1943) , and Herbert (1949) did not support the growth of any of the 27 strains available in this laboratory. This report describes the.development of a chemically defined medium which was evaluated in terms of the following criteria: yields of viable cells, minimum size of inoculum, suitability for maintamin g virulence on repeated subculture, and as a solid
more » ... um. METHODS AND MATERIALS Stock cultures were ntained at 5 C on nutrient agar-horse blood (5 per cent) slants. Virulent strains were injected into guinea pigs at approximately 6month intervals, the orga ns recovered from the infected spleens and used for preparing fresh stock slants. The virulence of the cultures for mice was assayed by subcutaneous inoculation, and LD,o values were calculated by the method of Reed and Muench (1938). Only unselected, thoroughly washed organisms were used in testing the synthetic casen medium. The cells were carefully removed from stock slants and washed in 3 to 5 changes of Sorensen's phosphate buffer (0.03 m, pH 7.2). The size of the inoculum was approximated turbidimetrically and the number of viable cells was determined by surface plating. The use of small numbers of washed, unselected organi minimized any influence on growth which might result from a carryover of nutrient materials or from the selection of variants capable of growth in the chemically defined medium. The composition of the medium, which is designated SC (synthetic casein) because it approximates the amino acid composition of casein, is shown in table 1. The amino acid concentrations were based on data for the composition of casein from Cohn and Edsal (1943) . Although added growth factors are not needed for growth in the synthetic casein medium, certain ones are listed in the table to record those which were tested and to which reference is made in the text. The usual stringent precautions were observed in preparing glassware and
doi:10.1128/jb.63.6.785-794.1952 fatcat:u2mmziq2m5ampbodtabtdvozeu