88 



CARBON NUTRITION 



360- 



240- 



a> 

 E 



c 



120 



40 80 120 



Time, hours 



160 



Figure 3. The formation of 

 /3-galactosidase (lactase) by 

 resting mycelium of Neurospora 

 crassa. Arrows indicate time 

 of exposure to the inducing 

 sugar. Redrawn from O. E. 

 Landman, Archives of Bio- 

 chemistry and Biophysics Vol. 

 52, p. 93-100 (1954), by per- 

 mission of Academic Press, Inc. 



themselves support growth only after a long lag, may be explained 

 by postulating that the glucose allows sufficient growth so that an 

 enzyme essential to fructose or mannose utilization can be synthesized. 

 Naturally, some energy must be available for the enzyme synthesis; 

 for resting cells endogenous reserves may be adequate, but with a 

 spore inoculum an exogenous energy source may be necessary. 



Extensive data on the utilization of mixed carbon sources have 

 been reported by Lilly and Barnett (116). Several fungi, e.g., Sordaria 

 fimicola and Thielaviopsis basicola, behave in accordance with the 

 foregoing postulate — they grow on a disaccharide, melibiose for exam- 

 ple, only if a utilizable monosaccharide is available. However, results 

 with Gliomas tix convoluta are not entirely explicable on this basis, 

 unless we postulate, without proof, that the sugar which supplies 

 energy for enzyme synthesis must be present in relatively high concen- 

 tration. These experiments are complicated by the inclusion of 

 asparagine, which supplies some carbon, in the basal medium. 



The results of Steinberg (194) on the utilization of mixed carbon 

 sources by Aspergillus niger are not satisfactorily explained by the 

 hypothesis of enzyme induction. Here a mixture of two unutilizable 

 compounds supports good growth. It is clear, from these results and 

 from those mentioned in the preceding paragraph, that the interaction 

 of different carbon sources requires further study. 



