234 



ZINDER AND LEDERBERG 



tucky, S. Wichita, S. urbana, S. habana, 

 S. altendorf, S. vejle, S. montevideo, 

 E. coli 1, E. coli 2, E. colt 5, E. coli 

 K-12, S. bonariensis, S. florida, and 5. 

 madelia. 



Inter-type transductions. It is not 

 known whether the adsorption of FA 

 is sufficient to indicate susceptibility to 

 genetic transfer, but preliminary data 

 identify a possible receptor group, 

 among which inter-type transductions 

 may be possible. 



5. typhi and S. typhimiiriiim differ 

 in a number of cultural and serological 

 characters. The latter ferments both 

 arabinose and rhamnose while the 

 former does not ferment and is in- 

 hibited by either of these sugars. 5. 

 typhi Watson V was exposed to FA 

 from S. ty phimuriiim and inoculated 

 into Durham fermentation tubes con- 

 taining one per cent of either sugar in 

 nutrient broth. After 24 hours a more 

 luxuriant growth appeared in the FA 

 treated cultures, and acid was pro- 

 duced by 48 hours. From these tubes 

 cultures were isolated that differ from 

 S. typhi only in their ability to fer- 

 ment these sugars. The control cul- 

 tures, without FA, show little evidence 

 of growth and no evidence of fermen- 

 tation. Although 5. typhifmiriimi pro- 

 duces gas from rhamnose and ara- 

 binose, these new forms remain typic- 

 ally anaerogenic. The experiment has 

 also been conducted on agar. Treated 

 cells were plated on EMB arabinose 

 and EMB rhamnose. S. typhi occasion- 

 ally mutates to a noninhibited form 

 (Kristensen, 1948) which was repre- 

 sented by white papillae which were 

 observed on both the experimental and 

 control plates. However, the purple 

 (fermenting) papillae were observed 

 only on the experimental plates. Cul- 

 turally they resembled the fermenting 

 strains isolated after transduction in 

 broth. These results have been repeated 

 with tv^'o other strains of S. typhi. 



Using a streptomycin resistant mutant 

 of S. typhimiiriimi as the source of FA, 

 it has been possible to transfer this 

 character to 5. typhi. Attempts to pro- 

 duce aerogenic fermentation of glucose 

 by 5. typhi by treatment with FA have 

 ail met with failure, possibly owing to 

 insufficiently selective conditions to 

 detect cells transduced for this char- 

 acter. 



5. typhi is antigenically character- 

 ized IX, XII: d, (monophasic) 



while 5. typhimurium is I, IV, V, XII: 

 / — 1, 2, 3. 5". typhi was exposed to FA 

 from S. typhimurium, and transduction 

 of the flagellar antigen was selected 

 for. A tube based upon the myco- 

 logical growth tube (Ryan et al., 1943) 

 was half filled with soft agar contain- 

 ing diluted anti-<^ serum (1/200 of 

 serum titrating to 1/5,000). The cells 

 w^ere heavily inoculated at one side of 

 the tube and watched for migration. 

 In one experiment, two out of four 

 experimental tubes showed migration 

 while the three control tubes showed 

 complete fixation of the inoculum. 

 There was a sharp delineation between 

 the migrating cells and the fixed inocu- 

 lum. The former were fished from the 

 uninoculated end of the tube and 

 tested culturally and serologically. 

 Both of the isolates culturally resem- 

 bled 5. typhi. One of them reacted 

 with anti-i serum while the other did 

 not react with either 5. typhi or S. 

 typhimurium flagellar antiserum and 

 was diagnosed as a ;' phase (KaufT- 

 mann, 1936). The analysis of these two 

 strains was confirmed by Dr. P. R. 

 Edwards. Transduction of the /' anti- 

 gen was obtained from twelve of 

 thirty-one tested inocula of 10^ FA 

 saturated 5. typhi cells, "f phases have 

 appeared occasionally in both experi- 

 mental and control tubes. No / phases 

 were detected in 50 control tests with- 

 out FA. The complete antigenic analy- 

 sis of the "hybrids" is IX, XII: /', . 



