GENE CONVERSION 26-12 



Experiment I. If the "extra" fermenters were the result of the 

 transfer of a substrate -dependent cjrtoplasmic entity, they should 

 lose their ability to ferment in the absence of substrate. Conse- 

 quently, cultures 1194, 1195, 1196, 1197, 1198, 1199, 1200, 1201, 

 1208, 1209, 1210, 1211, and their parents 554, 557, 571, and 573 

 were transferred daily in glucose broth for 11 successive transfers 

 and then tested on glucose, galactose, melibiose, and maltose in the 

 standard manner in small fermentation tubes. No previous nonfer- 

 menters fermented a new sugar. The only exception to the diagno- 

 sis made according to our regular custom immediately after isola- 

 tion, was that culture 557 failed to ferment maltose until after 12 

 days, and a subculture remained negative. The interesting thing is 

 that 1194, 1195, 1196, 1197, and 1198 which had received their abil- 

 ity to ferment maltose from 557 were apparently stable. 



Experiment n. Cultures 1208, 1209, 1210, and 1211 were shak- 

 en in M/30 KH2PO4 without substrate for 8 days; then aliquots were 

 taken from each flask and each aliquot was "fed" a few drops of 

 either (1) glucose or (2) galactose or (3) melibiose or (4) maltose 

 or (5) starved. This was done in the hope of "deadapting" the cells 

 by forcing them to form adaptive enzymes to other substrates. 

 Starvation was then continued for 10 days. Then glucose was added 

 to each for 1 day; the cultures were streaked, 2 colonies were se- 

 lected at random from each plate; these were combined, suspended 

 in buffer, and used to inoculate separate broth fermentation tubes 

 containing the 4 different sugars: glucose, galactose, melibiose, 

 and maltose. All cultures fermented rapidly (1-3 days) with the 

 following exceptions: (1) 1210 from glucose to galactose, 6 days; 

 (2) 1210 from maltose to galactose, 4 days; (3) 1208 from maltose 

 to galactose, 4 days. However, 1210 initially required 5 days to 

 ferment galactose and 1208 was also slow on galactose initially. 

 Therefore, this extensive attempt to remove "cytoplasmic" com- 

 ponents was completely negative. In fact, the only diminution was 

 in a parent which must have carried a fermenter gene for many 

 tetrads which originated from it subsequently segregated regular- 

 ly. The precaution of setting up one glucose tube as a control for 

 the detection of "dead" cultures was unnecessary. 



Experiment HI. Since mass transfers might have maintained 

 mixtures (which could be separated by colony isolation) 5 individual 

 colonies each from 573, 1208, 1209, 1210 and 1211 were tested on 

 the 4 sugars according to the procedure outlined above. There were 

 only 2 exceptions: 2 isolates of 1208 failed to ferment maltose. 



Experiment IV. Then five colonies were isolated from each 

 of the "treated" cultures (starved or fed one of the four sugars) de- 

 rived from culture 1208 from Experiment II (a total of 30 cultures). 

 These 30 cultures were transferred in glucose broth for 11 succes- 

 sive days and each of the five transfers from (1) the original tube. 



