348 BACTERIOLOGICAL CHEMISTRY 



in which the glucose units are united though the 1 : 6 

 positions. 



Some strains of Str. salivarius and of Sir. bovis syn- 

 thesise a water insoluble dextran, [a]i) + 180°, from 

 sucrose or raffinose, as does Betabacterium verrniforme 

 (probably a Lactobcicillus) from sucrose but not from 

 other sugars. This dextran, too, has [a]o+180° when 

 dissolved in acid or alkali. It is made up of « -glucose 

 units linked through positions 1 : 6, that is, it has the 

 gentiobiose structure. 



Phytomonas tumefaciens excretes into the medium a 

 polysaccharide which has [a]^^-9°, yielding only glu- 

 cose on hydrolysis. Its molecular weight, about 3600, 

 indicates that it is built up of 22 glucose units, probably 

 of pyranose form and joined by ^-linkages. 



Leuconostoc dextranicum, when grown on sucrose, 

 gives a mixture of dextran and a fructosan, but when 

 grown on glucose it yields mainly the dextran and very 

 little fructosan. 



Azotobacter chroococcum gives rise to a gum which 

 appears to consist mainly of an araban since it yields 

 arabinose on hydrolysis. The root nodule bacteria, 

 Bhizobium, also produce a gum which splits up into 

 glucuronic acid, CH0H-(CH0H)3-CH-C00H , and 



glucose on hydrolysis. ! q ^ 



It gives cross reactions with antisera to Types III, 

 VI and XIV pneumococci, probably due to a common 

 cellobiiironic acid structure. The Rh. radicicolum poly- 

 saccharide has the structure : — 



~ H OH CH2O H OH ~ 



— O— , / \ H H / 0\ 



OH H 

 H 



-0— 1\ OH H 



H \| 0/ N K H H 



OH H OH OH 



-0- /I !\ H 



/ OH H \, 



|\ H /l-O- 



