POLYSACCHARIDES OF MICRO-ORGANISMS 



340 



\\liicli vsliould be compared with that giv^en for Type III 

 pneumococciis on p. 356. 



B. rnesentericus and B. suhtilis when grown on sucrose 

 or raffinose produce levan, a laevo rotatory polysaccharide, 

 [a]D-45-3°, built up of fructofuranose units linked 

 together through positions 2 and 6 : — 



It is not formed when the organisms are growai on melezi- 

 tose, maltose, lactose, glucose, xylose or fructose. That 

 is, a terminal fructofuranose grouping, such as is present 

 in sucrose, 



HCOH 



I 

 HOCH 



I 

 HCOH 



CH 



I 

 CHaOH 



(glucose) 



CH2OH 



(fructofuranose) 



