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217 



THE BACTERIAL ORIGIN OF THE GUMS OF THE 

 ARABIN GROUP. 



XI. — The Nutrition of Bacterium acaci^e. 



By R. Greig Smith, D.Sc, Macleay Bacteriologist to the 



Society. 



(Plates xi.-xii.) 



In the first two papers of this series it was shown that when 

 £acf. acacim and JBact. metarahinum were sown upon the surfaces 

 of plates of saccharose-potato-tannin agar, they produced 

 luxuriant slimes, and that from the slimes arabin and metarabin 

 could be obtained. Since the medium produced so much slime it 

 was extremely probable that it contained the nutrients which 

 were best adapted to assist the bacteria in producing gum. The 

 medium consisted of saccharose 5%, tannin 0*3%, agar 2%, and 

 potato-juice or extract. The latter is the unknown quantity. 

 It would be necessary to determine the composition of the potato- 

 juice to arrive at a knowledge of the nutrition of the bacteria, 

 and two methods might be adopted for this purpose. Either the 

 juice may be analysed, or one might experiment with various 

 single nutrients in the hope of finding a clue which would lead 

 to the desired end. I chose the latter alternative, chiefly because 

 by doing so there was the probability of increasing the yield of 

 slime by using nutrients which might not be in potato-juice. 



Preliminary experiments. — According to Dammar and Rung 

 (Chemisches Handworterbuch), potato-extract should contain 

 reducing sugars, 'asparagine, traces of amido-acids, peptone, 

 solanine and gums. The albuminoids would be removed during 

 the preparation of the extract. The chief of these nutri.e^nts are 

 the reducing sugars and the asparagine; the other constituents 

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