primer. We axe going to look for enzymes which 

 could accumulate cellodextrins during develop- 

 ment. 



PAPACONSTANTINOU: Does this cell wall 

 preparation include both spore and stalk? 



B. WRIGHT: Yes, we've looked at both and, 

 from staining reactions with iodine and various 

 other things, we feel that the glycogen moiety is 

 present in both equally. Thus, we think that the 

 material that Gezelius and Ranby studied was, 

 in fact, the material we are studying. This 

 could explain their description of amorphous 

 cellulose, if it really was 50% amorphous 

 glycogen. 



PAPACONSTANTINOU: How can you postu- 

 late the linkage of the glycogen and the cellu- 

 lose? How do you picture it? 



B. WRIGHT: Well, we tried to separate 

 them physically with urea and high salt concen- 

 trations, etc., with very little success. Maybe 

 you could get a very tight physical binding be- 

 tween the cellulose and the glycogen. 



PAPACONSTANTINOU: What I'm wonder- 

 ing is, is it possible that there's an enzyme that 

 is actually attaching alpha- 1, 4 linkages to some 

 part of the cellulose in a straight line of beta-1, 

 4's? 



B. WRIGHT: Yes. 



PAPACONSTANTINOU: You have a free 

 hydroxyl in the 6 position of the hexoses in 

 cellulose and you may be getting an alpha-1, 

 6 to start off the glycogen which will then be a 

 series of alpha-1, 4 linkages. 



B. WRIGHT: We have preliminary evidence 

 for contaminating maltose in the cellulose frac- 

 tion and cellobiose in the glycogen fraction. 



PAPACONSTANTINOU: Oh, fine. 



B. WRIGHT: However, this is all very ten- 

 tative because you don't know how clean the 

 preparations are. There is a soluble fraction 

 and an insoluble fraction, but in each there 

 could be small amounts of the other that were 

 not actually attached. The amount of the radio- 

 active cellobiose is so small that we don't like 

 to make any definite statements until we get 

 more of it. Maybe we can trick the in vitro sys- 

 tem into making more of the cellulose fraction 

 and really analyze it. 



GROSS: How much galactose is in the cell 

 wall? 



B. WRIGHT: I don't know. I guess Maurice 

 Sussman has data on that. Now, his material is 

 soluble, of course; ours is an insoluble poly- 

 saccharide. We've looked for galactose in our 

 preparations and found none. This cell wall 

 material has been accounted for by weight, and 



it is pretty well characterized as a 50-50 mix- 

 ture of cellulose and glycogen. 



GROSS: Well, where is the product of that 

 UDP-galactose transferred? 



B. WRIGHT: That's on the surface, isn't 

 it? 



HANKS: I believe it's associated with the 

 cell wall. 



B. WRIGHT: Yes. 



CANTING: Do you know anything about the 

 average chain length of the glycogen? 



B. WRIGHT: We are now doing that en- 

 zymatically with a combination of phospho- 

 rylase and amylo-1, 6-glucosidase, determining 

 glucose and glucose- 1 -phosphate. Wedon'tknow 

 yet. 



CANTING: I wondered whether it might be 

 changing at the spore stage as compared to the 

 other stages. 



B. WRIGHT: We want to look into that and 

 compare the cell wall glycogen, after it's been 

 separated from cellulose, to the pellet glycogen. 

 Perhaps the cell could be insolubilizing the 

 pellet glycogen, so to speak, as a primer. It'll 

 be interesting if the amoeba membrane enzyme 

 is similar to the cell wall enzyme. It reacts to 

 EDTA the same, and it may be that we can't 

 detect it in its potential role in cell wall syn- 

 thesis because of the lack of alkali-insoluble 

 material. The enzyme may be there earlier, 

 but not bound to insoluble material. 



TS'O: I'd like to raise some, perhaps, naive 

 questions which have been bothering me. In dif- 

 ferentiation, probably the most interesting event 

 is the decision-making process. You have dis- 

 cussed the enzyme-inhibitor levels and rate- 

 limiting processes. I wonder, how do these 

 relate to the real decision-making process? 



B. WRIGHT: I think it is wrong to think in 

 terms of an important decision-making phe- 

 nomenon; I think this never exists. This is a 

 very complex interaction of many things, and 

 it's misleading to look for the one cause. 



GROSS: However, that might be precisely 

 why decision- making is absolutely important. 

 There may be two alternative steps, two stable 

 states, each self-stabilizing as it matures, but 

 one small thing may be the deciding factor. 



B. WRIGHT: However, here we have shown 

 there are numerous small things that are de- 

 ciding factors, since they are all limiting. 



GROSS: Yes, but in vivo presumably only 

 one of them is active. 



B. WRIGHT: No. This is a very complex 

 steady state situation which is as stable as it 

 is and as reproducible as it is precisely be- 



118 



