Formates by B. coli communis. 



465 



be produced from the carbohydrate. A convenient mixture is 1*5 per cent, 

 carbohydrate and - 5 per cent, sodium formate in 1 per cent, peptone water. 

 It will be found under these circumstances that whereas an organism may 

 give only a few bubbles, or even no gas at~all, from sodium formate peptone 

 water alone, and none at all from glucose peptone water alone, the mixture 

 may yield gas with great rapidity, so that in 20 hours a Durham tube may 

 be completely filled. This increased gas production is due chiefly to the 

 decomposition of the formate, but partly also to gas which may be produced 

 from the sugar when the solution is maintained neutral, as will be described 

 later. 



This increased gas production from formates in the presence of carbo- 

 hydrates is strikingly illustrated in the case of a selected strain of 

 B. coli communis obtained by the chloroacetate method, as will be seen from 

 the following table. The numbers represent millimetres of the tube 

 occupied by gas in the Durham tubes of 45 mm. length. 



Table II. — The Effect of Addition of Carbohydrates and Allied Substances 

 on the Decomposition of Sodium Formate by an Artificially Selected 

 Strain of B. coli communis producing only a Minute Quantity of Gas 

 from Glucose. 



Time. 



Sodium 

 formate. 



Glucose. 



Lactose. 



Mannitol. 



Dulcitol. 



Sorbitol. 



Glycerine. 





(Concentration of the Sugar or Alcohol 2 per cent.) 





hours. 

















12 



Nil 



Nil 



Nil 



Trace 



Nil 



Trace 



Nil 



24 



J) 



>) 



» 



11 





12 





36 





Minute 

 bubble 



Minute 

 bubble 



23 



Ji 



25 



J) 



60 



5> 



No increase 



0-5 



No increase 





No increase 



Trace 



84 



>) 





2 -0 



>> 



3 



>> 



1 



108 



)> 



)i 



3-0 



>) 



30 





1 



132 



JJ 





3-0 



)j 



37 



>> 



1 



Evolution of Gas from the above Carbohydrates and Alcohols after 







Admixture with Sodium Formate. 







(Carbohydrate or Alcohol 1*5 per cent., Sodium Formate - 5 per cent.) 



12 





12 



4-0 



Trace 



Nil 



2 



Nil 



24 





Full 



Full 



10 





10 





36 









34 





Full 





60 









Full 







5 



84 











5 





7 



The following facts should be noted in connection with the experiment 

 described above : — 



