THE GROWTH OF SACCHARIDE IMACROMOLECULES 319 



incorporation reaction involves a polyrepetitive process rather than the 

 transfer of one or only a few glucose residues to the acceptor site. Hence, 

 one cannot be confident that this system is indeed one of complete cellulose 

 synthesis by a cell-free agent. Nor can it as yet be asserted with any con- 

 fidence that the major donor system involved in cellulose synthesis by this 

 bacteria is indeed UDPG itself rather than an analogue thereof. 



Fig. 3. Morphological elements in cellulose formed from glucose in a dilute 

 suspension of cells of Acetobacter xylhnitn. In addition to the elements listed in 

 the legend of Fig. 2, this field reveals characteristic arrangements ("mats") of 

 polymer in parallel rows of granules or rods apparently patterned by an enclosed 

 framework of ultrastrands. Technique as in Fig. 2, except for the use of a longer 

 reaction time (about 2 hr.). Magnification x 25 000. (Electronmicrograph prepared 

 by Dr. D. Danon and Mr. I. Ohad.) 



A production of electron-microscopically demonstrable cellulosic 

 fibre has been observed by Colvin [8] in A. xyliniim homogenates in- 

 cubated with glucose in presence of adenosine triphosphate. Colvin has 

 also reported that an ethanol extract made from a suspension of cells 

 incubated with glucose contains a solute which on transfer to water assumes 

 a fibrillar form, is alkali-insoluble, and affords glucose on acid hydrolysis. 

 When such an ethanol extract was heated and then supplemented with an 

 ultrafiltered Acetobacter preparation (aqueous extract of a dried suspension 



