1923) 



CAMP — CITRIC ACID AS A SOURCE OF CARBON 



253 



of sugar used but without the citric acid, using KNO. as nitrogen 



grown in triplicate in 100-cc. flasks, 





source. 



The fungi were 



and the results are found in table ix, the weights of the mats 

 representing averages of 3. 



TABLE IX 



GROWTH OF FUNGI ON CITRATE WITH VARIOUS N SOURCES 



Mineral nutrients, regular cone. 



Mineral nutrients, ^ cone. 



Daya 



KNO, 



[ Pep- 



NH,NO, tone 



Blank 



167 



199 



225 





20 



209 



208 



213 





20 



47 



111 



168 





33 



297 



347 



325 



22 



22 



160 



171 



155 



15 



22 



210 



134 



273 



13 



45 



44 



75 



151 



14 



28 



280 



275 



295 



16 



20 



From these experiments we may draw certain general con- 

 clusions to be used in future culture work. None of the fungi 

 would make any rapid or luxuriant growth with the citrate 

 ion as the sole source of carbon but some would utilize it if a little 

 sugar was allowed at the start. Organisms 2, 3, 9, and probably 



I 



6, grew very well on the free citric acid, unneutralized, after they 

 were once started with a small amount of sugar (1 gm. per liter 

 was sufficient). Organisms 4, 5, 7, 11, and probably 16 (judging 

 from later work), would not make more than slight use of un- 

 neutralized citric acid even after being given a good start with 

 sugar, the free citric acid being probably lethal to the mycelium. 

 In most cases peptone was the best source of nitrogen in connec- 

 tion with the citrate radical, although there was no considerable 

 advantage over KNOi or NH«NO, in many cases, and with Dip- 

 lodia NH<NO» would seem to make a more favorable nitrogen 

 source than either peptone or KNO* In interpreting the results 

 where various sources of nitrogen were used it is to be noted that 

 Phomopsis Citri and Penicillium digitatum showed very little 

 use of citric acid and that Alternaria Citri showed little use in 

 the presence of KNO t and NH 4 NOi. None of these results are 

 to be taken as final in any sense. No culture work which only 



