3l8 SHLOMO HESTRIN 



Z. Gromet-Elhanan in our laboratory likewise attempted to repeat the 

 result described by Greathouse, and used for this purpose the same strain 

 in conditions which resembled as closely as possible those used by the 

 earlier workers. We have been unable in our laboratory to obtain any 

 significant synthesis of cellulose in this homogenate system. 



Fig. 2. Cellulose fibres formed from glucose in a dilute suspension of cells of 

 Acetobacter xyliuiim. Fine filaments (" ultrastrands "), whose thickness as estimated 

 by measurement of shadow length is about 15 A, are seen both in solitary dis- 

 positions and in intertwisted bundles ("composite fibre"). Along the length of 

 some of the latter, aggregations of rods and granules ("amorphous formations") 

 are seen. Photograph was taken at a reaction time of 20 min. Intercellular space 

 at zero time was free from polymer. Specimen is mounted on a collodion film and 

 was freed from non-polymeric solutes by filtration over agar (Kellenberger's 

 technique). Pt shadow-cast (shadow ratio, i :6). Ahignification x 50000. (Elec- 

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



The work of Glaser [7] has demonstrated that UDPG labelled in the 

 glucose moiety incorporates ^^C into cellulose in the presence of a sub- 

 cellular particle prepared from A. xylinmn. Mr. I. Ohad in our laboratory 

 has successfully repeated this experiment. However, it should be noted 

 that the cellulose-synthesizing activity manifested by this particle prepara- 

 tion is very poor. It has, moreover, not as yet been shown that the observed 



