541 



THE BACTERIAL ORIGIN OF THE GUMS OF THE 

 ARABIN GROUP. 



X. — The Pararabin Gum of Sterculia. 



{BaCT, PARARABINUM, n.Sp.) 



Bv^ R. Greig Smith, D.Sc, Macleay Bacteriologist to the 



Society. 



The gum which sometiilies exudes from specimens of Sterculia 

 has been investigated by Maiden,* who found that it consisted 

 essentially of arabin and pararabin. f The latter is presumably 

 a modification of the former, and differs from it in being insoluble 

 in water. Pararabin also differs from arabin, as well as from 

 metarabin or cerasin, in not being hydrolysed upon boiling with 

 dilute sulphuric acid. 



I have already shown that arabin is the product of Bact. 

 acacice, and that metarabin is produced by Bact. metarahinum. 

 It would, therefore, be interesting if an organism capable of 

 forming pararabin could be isolated. Such a result would not 

 only show how diverse can be the gum-products of bacteria, but 

 also how the gums, which were supposed to be secretions of the 

 higher plants in a pathological condition and to have been pro- 

 duced from cellulose, are really the bj^products of the bacterial 

 fermentation of sugars. 



* Maiden, Pharm. Jour. [3] xx., 1890, 381. 

 t Pararabin found in beet-root, carrots, agar-agar, is amorphous, swells 

 in water, is soluble in dilute mineral acids, and is precipitated therefrom by 

 alkalies or alcohol; upon warming with alkalies gives arabin, with dilute 

 H0SO4 no sugar, does not decompose carbonates. — Dammer und Kung, 

 " Chemisches Handwurterbuch." 



